Dear community,

We recently got a non-public support request about handling drag and drop events for a custom image control in a dialog. And while we have shown this, drag event handling, multiple times before, I thought it does not hurt to answer this publicly, as this very case - an image control - is quite common, and it does not hurt having a bit more verbose public example for it.

edit: I have updated this topic with new code and a new video, to also handle outgoing asset drag events, and talk a bit about the pros and cons of different approaches, and what you could do when not implementing a code example as I did here, and therefore have a bit more leverage room when it comes to complexity.

In general, doing all this is possible. It is just that not everything is a ready-made solution for you, where you just call a function. At some point you have to "swim" here yourself, as we cannot write your code for you, but I hope the example helps shedding some light on the probably uncessarily complicated drag handling in Cinema 4D.

Cheers,
Ferdinand

Result

Code

"""Provides an example for implementing a custom control that can generate and receive drag events.

The example implements a dialog which holds multiple "cards" (BitmapCard) that display an image
and can receive drag events. The user can drag images from the file system into these cards (file
paths) or drag texture assets from the Asset Browser into these cards. The cards can also generate
drag events themselves, e.g., when the user drags from a card, it will generate a drag event. 
Showcased (selectable via the combo box in the menu of the dialog) are three drag types:

1. File paths: Dragging a card will generate an image file path drag event, which for example could 
   be dragged into a file path field of a shader, onto an object in the viewport, or onto other 
   BitmapCard controls. The advantage of this approach is that we do not have to create
   materials or assets, but can just use the file path directly.

2. Materials: Dragging a card will generate an atom drag event, here populated with a Redshift
   material that has the texture of the card as an input. This material can then be dragged onto
   anything that accepts materials, like objects in the viewport. The disadvantage of this
   approach is that we have to create a material, and that we have to exactly define how the 
   material is constructed.

3. Assets: Dragging a card will generate an asset drag event, here populated with a texture asset
   that has the texture of the card as an input. This asset can then be dragged onto anything that
   texture accepts assets, such as an object in the viewport. The disadvantage of this
   approach is that we have to create an asset.

   - The example also showcases a variation oof this approach, where we exploit a bit how the
     texture asset drag handling works, to avoid having to create an asset.


Overview:

- BitmapCard: A user area control that can receive drag events and generate drag events itself. Here
              you will find almost all the relevant code for drag and drop handling
- BitmapStackDialog: A dialog that holds multiple BitmapCard controls and allows the user to select
                the drag type via a combo box. This dialog is the main entry point of the example
                but does not contain much relevant code itself.
"""
__author__ = "Ferdinand Hoppe"
__copyright__ = "Copyright 2025 Maxon Computer GmbH"

import os
import re

import c4d
import maxon
import mxutils

# The file types that are supported to be dragged into a BitmapCard control.
DRAG_IN_FILE_TYPES: list[str] = [".png", ".jpg", ".jpeg", ".tif"]

# A regex to check of a string (which is meant to be a path/url) already as a scheme (like file:///
# or http:///). The protocol we are mostly checking for is "asset:///", but we keep this regex generic
# to allow for other schemes as well.
RE_URL_HAS_SCHEME = re.compile("^[a-zA-Z][a-zA-Z\d+\-.]*:\/\/\/")

# A non-public core message which need when we want to properly generate asset drag events.
COREMSG_SETCOMMANDEDITMODE: int = 300001000


class BitmapCard(c4d.gui.GeUserArea):
    """Implements a control that can receive bitmap path drag events and generates drag events itself.
    """

    def __init__(self, host: "BitmapStackDialog") -> None:
        """Constructs a new BitmapCard object.
        """
        # The host dialog that holds this card. This is used to access the drag type selected in the
        # combo box of the dialog.
        self._host: BitmapStackDialog = host

        # The image file path and the bitmap that is displayed in this card.
        self._path: str | None = ""
        self._bitmap: c4d.bitmaps.BaseBitmap | None = None

    def GetMinSize(self) -> tuple[int, int]:
        """Called by Cinema 4d to evaluate the minimum size of the user area.
        """
        return 250, 100

    def DrawMsg(self, x1, y1, x2, y2, msg_ref):
        """Called by Cinema 4D to let the user area draw itself.
        """
        self.OffScreenOn()
        self.SetClippingRegion(x1, y1, x2, y2)

        # Draw the background and then the bitmap if it exists. In the real world, we would have to
        # either adapt #GetMinSize to the size of the bitmap, or draw the bitmap in a way that it
        # fits into the user area, e.g., by scaling it down. Here we just draw it at a fixed size.
        self.DrawSetPen(c4d.gui.GetGuiWorldColor(c4d.COLOR_BGGADGET))
        self.DrawRectangle(x1, y1, x2, y2)
        if self._bitmap:
            w, h = self._bitmap.GetSize()
            self.DrawBitmap(self._bitmap, 5, 5, 240, 90, 0,
                            0, w, h, c4d.BMP_NORMALSCALED)

    def Message(self, msg: c4d.BaseContainer, result: c4d.BaseContainer) -> int:
        """Called by Cinema 4D to handle messages sent to the user area.

        Here we implement receiving drag events when the user drags something onto this user area.
        """
        # A drag event is coming in.
        if msg.GetId() == c4d.BFM_DRAGRECEIVE:
            # Get out when the drag event has been discarded.
            if msg.GetInt32(c4d.BFM_DRAG_LOST) or msg.GetInt32(c4d.BFM_DRAG_ESC):
                return self.SetDragDestination(c4d.MOUSE_FORBIDDEN)

            # Get out when this is not a drag type we support (we just support images). Note that we
            # cannot make up drag types ourselves, so when we want to send/receive complex data, we
            # must use the DRAGTYPE_ATOMARRAY type and pack our data into a BaseContainer attached
            # to the nodes we drag/send.
            data: dict = self.GetDragObject(msg)
            dragType: int = data.get("type", 0)
            if dragType not in [c4d.DRAGTYPE_FILENAME_IMAGE, maxon.DRAGTYPE_ASSET]:
                return self.SetDragDestination(c4d.MOUSE_FORBIDDEN)

            # Here we could optionally check the drag event hitting some target area.
            # yPos: float = self.GetDragPosition(msg).get('y', 0.0)
            # if not 0 < yPos < 50 or not self.CheckDropArea(msg, True, True):
            #     return self.SetDragDestination(c4d.MOUSE_FORBIDDEN)

            # After this point, we are dealing with a valid drag event.

            # The drag is still going on, we just set the mouse cursor to indicate that we are
            # ready to receive the drag event.
            if msg.GetInt32(c4d.BFM_DRAG_FINISHED) == 0:
                return self.SetDragDestination(c4d.MOUSE_MOVE)
            # The drag event is finished, we can now process the data.
            else:
                # Unpack a file being dragged directly.
                path: str | None = None
                if dragType == c4d.DRAGTYPE_FILENAME_IMAGE:
                    path = data.get("object", None)
                # Unpack an asset being dragged.
                elif dragType == maxon.DRAGTYPE_ASSET:
                    array: maxon.DragAndDropDataAssetArray = data.get(
                        "object", None)
                    descriptions: tuple[tuple[maxon.AssetDescription, maxon.Url, maxon.String]] = (
                        array.GetAssetDescriptions())
                    if not descriptions:
                        # Invalid asset but we are not in an error state.
                        return True

                    # Check that we are dealing with an image asset.
                    asset: maxon.AssetDescription = descriptions[0][0]
                    metadata: maxon.BaseContainer = asset.GetMetaData()
                    subType: maxon.Id = metadata.Get(
                        maxon.ASSETMETADATA.SubType, maxon.Id())
                    if (subType != maxon.ASSETMETADATA.SubType_ENUM_MediaImage):
                        # Invalid asset but we are not in an error state.
                        return True

                    path = str(maxon.AssetInterface.GetAssetUrl(asset, True))

                if not isinstance(path, str):
                    return False  # Critical failure.

                if (dragType == c4d.DRAGTYPE_FILENAME_IMAGE and
                    (not os.path.exists(path) or
                     os.path.splitext(path)[1].lower() not in DRAG_IN_FILE_TYPES)):
                    # Invalid file type but we are not in an error state.
                    return True

                self._path = path
                self._bitmap = c4d.bitmaps.BaseBitmap()
                if self._bitmap.InitWith(path)[0] != c4d.IMAGERESULT_OK:
                    return False  # Critical failure.

                self.Redraw()  # Redraw the user area to show the new bitmap.

                return True

        # Process other messages, doing this is very important, as we otherwise break the
        # message chain.
        return c4d.gui.GeUserArea.Message(self, msg, result)

    def InputEvent(self, msg: c4d.BaseContainer) -> bool:
        """Called by Cinema 4D when the user area receives input events.

        Here we implement creating drag events when the user drags from this user area. The type of
        drag event which is initiated is determined by the drag type selected in the combo box
        of the dialog.
        """
        # When this is not a left mouse button event on this user area, we just get out without
        # consuming the event (by returning False).
        if (msg.GetInt32(c4d.BFM_INPUT_DEVICE) != c4d.BFM_INPUT_MOUSE or
                msg.GetInt32(c4d.BFM_INPUT_CHANNEL) != c4d.BFM_INPUT_MOUSELEFT):
            return False

        # Get the type of drag event that should be generated, and handle it.
        dragType: int = self._host.GetInt32(self._host.ID_DRAG_TYPE)
        return self.HandleDragEvent(msg, dragType)
    
    # --- Custom drag handling methods -------------------------------------------------------------

    # I have split up thing into three methods for readability, this all could also be done directly
    # in the InputEvent method.

    def HandleDragEvent(self, event: c4d.BaseContainer, dragType: int) -> bool:
        """Handles starting a drag event by generating the drag data and sending it to the system.

        This is called when the user starts dragging from this user area.
        """
        # This requires us to modify the document, so we must be on the main thread (technically
        # not true when the type is DRAGTYPE_FILENAME_IMAGE, but that would be for you to optimize).
        if not c4d.threading.GeIsMainThread():
            raise False

        # Generate our drag data, either a file path, a material, or an asset.
        doc: c4d.documents.BaseDocument = c4d.documents.GetActiveDocument()
        data: object = self.GenerateDragData(doc, dragType)

        # Now we set off the drag event. When we are dragging assets, we have to sandwich the event
        # in these core message calls, as otherwise the palette edit mode toggling will not work
        # correctly.
        if dragType == maxon.DRAGTYPE_ASSET:
            bc: c4d.BaseContainer = c4d.BaseContainer(
                COREMSG_SETCOMMANDEDITMODE)
            bc.SetInt32(1, True)
            c4d.SendCoreMessage(c4d.COREMSG_CINEMA, bc, 0)

        # When #HandleMouseDrag returns #False, this means that the user has cancelled the drag
        # event, one case could be that the user actually did not intend to drag, but just
        # clicked on the user area.
        #
        # In this case we remove the drag data we generated, as it is not needed anymore. Note that
        # this will NOT catch the case that the drag event is cancelled by the recipient, e.g., the
        # user drags a material onto something that does not accept materials.
        if not self.HandleMouseDrag(event, dragType, data, 0):
            self.RemoveDragData(doc, data)
            return True

        # Other half of the sandwich, we toggle the palette edit mode back to normal.
        if dragType == maxon.DRAGTYPE_ASSET:
            bc: c4d.BaseContainer = c4d.BaseContainer(
                COREMSG_SETCOMMANDEDITMODE)
            bc.SetInt32(1, False)
            c4d.SendCoreMessage(c4d.COREMSG_CINEMA, bc, 0)

        return True

    def GenerateDragData(self, doc: c4d.documents.BaseDocument, dragType
                         ) -> str | c4d.BaseMaterial | maxon.DragAndDropDataAssetArray:
        """Generates the drag data for the given drag type.

        Each tile just encapsulates a file path, but we realize dragging them as file paths,
        materials, or assets. So, when the type is material or asset, the drag data must be
        generated from the file path. Which is why we have this method here.
        """
        if not c4d.threading.GeIsMainThread():
            raise RuntimeError(
                "GenerateDragData must be called from the main thread.")

        # The user has selected "File" as the drag type, we just return the file path.
        if dragType == c4d.DRAGTYPE_FILENAME_IMAGE:
            return self._path
        # The user has selected "Material" as the drag type, we create a Redshift material with the
        # texture as input and return that material.
        elif dragType == c4d.DRAGTYPE_ATOMARRAY:
            material: c4d.BaseMaterial = mxutils.CheckType(
                c4d.BaseMaterial(c4d.Mmaterial))

            # Create a simple graph using that texture, and insert the material into the
            # active document.
            maxon.GraphDescription.ApplyDescription(
                maxon.GraphDescription.GetGraph(
                    material, maxon.NodeSpaceIdentifiers.RedshiftMaterial),
                {
                    "$type": "Output",
                    "Surface": {
                        "$type": "Standard Material",
                        "Base/Color": {
                            "$type": "Texture",
                            # Set the texture. When our source is a file we will just have a plain
                            # path, e.g. "C:/path/to/file.png" and we have to prefix with a scheme
                            # (file) to make it a valid URL. When we are dealing with an asset, the
                            # texture path will already be a valid URL in the "asset:///" scheme.
                            "Image/Filename/Path": (maxon.Url(f"{self._path}")
                                                    if RE_URL_HAS_SCHEME.match(self._path) else
                                                    maxon.Url(f"file:///{self._path}"))
                        }
                    }
                })
            doc.InsertMaterial(material)
            return [material]
        # The user has selected "Asset" as the drag type, we create a texture asset and return that.
        elif dragType == maxon.DRAGTYPE_ASSET:
            # So we have to cases here, either that we want truly want to generate an asset drag
            # event or that we just want to piggy-back onto the texture asset drag and drop
            # mechanism of Cinema 4D, which is what we do here.

            # Code for truly generating an asset drag event, where we would store the asset in the
            # scene repository.
            generateAssets: bool = False
            if generateAssets:
                # Get the scene repository and create an asset storage structure for the asset.
                repo: maxon.AssetRepository = doc.GetSceneRepository(True)
                store: maxon.StoreAssetStruct = maxon.StoreAssetStruct(
                    maxon.Id(), repo, repo)

                # Now save the texture asset to the repository.
                url: maxon.Url = maxon.Url(self._path)
                name: str = url.GetName()
                asset, _ = maxon.AssetCreationInterface.SaveTextureAsset(
                    url, name, store, (), True)

                # Create a drag array for that asset. It is important that we use the URL of the
                # asset (maxon.AssetInterface.GetAssetUrl) and not #url or asset.GetUrl(), as both
                # are physical file paths, and will then cause the drag and drop handling to use
                # these physical files, including the popup asking for wether the file should be
                # copied. We will exploit exactly this behavior in the second case.
                dragArray: maxon.DragAndDropDataAssetArray = maxon.DragAndDropDataAssetArray()
                dragArray.SetLookupRepository(repo)
                dragArray.SetAssetDescriptions((
                    (asset, maxon.AssetInterface.GetAssetUrl(asset, True), maxon.String(name)),
                ))

                return dragArray
            # With this case we can piggy-back onto the existing drag and drop texture asset
            # handling of Cinema 4D, without actually having to create an asset. THIS IS A
            # WORKAROUND, we could decide at any moment to change how the drag and drop
            # handling of assets works, possibly rendering this approach obsolete.
            else:
                # The slight disadvantage of this approach (besides it being a hack and us possibly
                # removing it at some point) is that we have to pay the download cost of
                # #self._host._dummyAssetId once. I.e., the user has to download that texture once
                # either by using it in the Asset Browser or by running this code. Once the asset has
                # been cached, this will not happen again.
                #
                # But since we search below in a 'whoever comes first' manner, what is the first
                # texture asset could change, and this could then be an asset which has not been
                # downloaded yet. So, in a more robust world we would pick a fixed asset below. But
                # this comes then with the burden of maintenance, as we could remove one of the
                # builtin texture assets at any time. So, the super advanced solution would be to
                # ship the plugin with its own asset database, and mount and use that. Here we could
                # use a hard-coded asset ID, and would have to have never pay download costs, as
                # the repository would be local.

                # Find the asset by its Id, which we have stored in the dialog.
                repo: maxon.AssetRepositoryInterface = maxon.AssetInterface.GetUserPrefsRepository()
                dummy: maxon.AssetDescription = repo.FindLatestAsset(
                    maxon.AssetTypes.File().GetId(), self._host._dummyAssetId, maxon.Id(),
                    maxon.ASSET_FIND_MODE.LATEST)

                # Setup the drag array with the asset. Note that #asset must be a valid texture
                # asset, so just passing maxon.AssetDescription() will not work. But the backend
                # for drag and drop handling will actually ignore the asset except for type checking
                # it, and use the URL we provided instead.
                dragArray: maxon.DragAndDropDataAssetArray = maxon.DragAndDropDataAssetArray()
                dragArray.SetLookupRepository(repo)
                dragArray.SetAssetDescriptions((
                    (dummy, maxon.Url(self._path), maxon.String(os.path.basename(self._path))),
                ))
            return dragArray
        else:
            raise ValueError(f"Unsupported drag type: {dragType}")

    def RemoveDragData(self, doc: c4d.documents.BaseDocument,
                       data: str | list[c4d.BaseMaterial] | maxon.DragAndDropDataAssetArray) -> bool:
        """Removes generated content when the user cancels a drag event.

        Sometimes the user starts a drag event, but then cancels it, e.g., by pressing the
        escape key. In this case, we have to remove the generated content, e.g., the material or
        asset that we created for the drag event.
        """
        if not c4d.threading.GeIsMainThread():
            return False

        if isinstance(data, list):
            # Remove the dragged materials from the document. Since we are always generating a new
            # material, we can just remove them. That is in general probably not the best design,
            # and a real world application should avoid duplicating materials.
            for item in data:
                if isinstance(item, c4d.BaseList2D):
                    item.Remove()
        elif isinstance(data, str):
            # Here we could technically remove a file.
            pass
        elif isinstance(data, maxon.DragAndDropDataAssetArray):
            # We could remove the asset, but other than for the material, there is no guarantee
            # that we are the only user of it, as the Asset API has a duplicate preventing
            # mechanism. So, the #SaveTextureAsset call above could have returned an already
            # existing asset. Since we could operate with a document bound repository, we could
            # search the whole document for asset references and only when we find none, remove
            # the asset.
            #
            # We use here the little hack that we actually do not create an asset, to just to piggy-
            # back onto the material drag and drop mechanism of assets, so we can just ignore
            # this case.
            pass

        return True


class BitmapStackDialog(c4d.gui.GeDialog):
    """Implements a a simple dialog that stacks multiple BitmapCard controls.
    """
    ID_DRAG_TYPE: int = 1002

    def __init__(self):
        """Constructs a new ExampleDialog object.
        """
        # The user area controls that will generate and receive drag events.
        self._cards: list[BitmapCard] = [
            BitmapCard(host=self) for _ in range(4)]

        # The id for the dummy asset that used to generate 'fake' texture asset drag events. We
        # search for it here once, so that we do not have to do it in the __init__ of each
        # BitmapCard, or even worse, in the HandleDragEvent of each BitmapCard.

        # We could technically also store here the AssetDescription instead of the Id, but that
        # reference can go stale, so we just store the Id and then grab with it the asset when we
        # need it. Which is much faster than searching asset broadly as we do here. In the end, we
        # could probably also do all this in the drag handling of the BitmapCard, but a little bit
        # of optimization does not hurt.
        self._dummyAssetId: maxon.Id | None = None
        if not maxon.AssetDataBasesInterface.WaitForDatabaseLoading():
            raise RuntimeError("Could not initialize the asset databases.")

        def findTexture(asset: maxon.AssetDescription) -> bool:
            """Finds the first texture asset in the user preferences repository.
            """
            # When this is not a texture asset, we just continue searching.
            meta: maxon.AssetMetaData = asset.GetMetaData()
            if (meta.Get(maxon.ASSETMETADATA.SubType, maxon.Id()) !=
                    maxon.ASSETMETADATA.SubType_ENUM_MediaImage):
                return True

            # When it is a texture asset, we store it as the dummy asset and stop searching.
            self._dummyAssetId = asset.GetId()
            return False

        # Search for our dummy asset in the user preferences repository.
        repo: maxon.AssetRepositoryInterface = maxon.AssetInterface.GetUserPrefsRepository()
        repo.FindAssets(maxon.AssetTypes.File().GetId(), maxon.Id(), maxon.Id(),
                        maxon.ASSET_FIND_MODE.LATEST, findTexture)

    def CreateLayout(self):
        """Called by Cinema 4D to populate the dialog with controls.
        """
        self.SetTitle("Drag and Drop Example")
        self.GroupSpace(5, 5)
        self.GroupBorderSpace(5, 5, 5, 5)

        # Build the combo box in the menu bar of the dialog.
        self.GroupBeginInMenuLine()
        self.GroupBegin(1000, c4d.BFH_LEFT | c4d.BFV_TOP, cols=2)
        self.GroupBorderSpace(5, 5, 5, 5)
        self.GroupSpace(5, 5)
        self.AddStaticText(1001, c4d.BFH_LEFT |
                           c4d.BFV_CENTER, name="Drag Events as:")
        self.AddComboBox(1002, c4d.BFH_RIGHT | c4d.BFV_TOP)
        self.GroupEnd()
        self.GroupEnd()

        # Add the BitmapCard controls to the dialog.
        for i, card in enumerate(self._cards):
            self.AddUserArea(2000 + i, c4d.BFH_LEFT | c4d.BFV_TOP)
            self.AttachUserArea(card, 2000 + i)

        # Add items to the combo box to select the drag type.
        self.AddChild(self.ID_DRAG_TYPE, c4d.DRAGTYPE_FILENAME_IMAGE, "Files")
        self.AddChild(self.ID_DRAG_TYPE, c4d.DRAGTYPE_ATOMARRAY, "Materials")
        self.AddChild(self.ID_DRAG_TYPE, maxon.DRAGTYPE_ASSET, "Assets")
        self.SetInt32(self.ID_DRAG_TYPE, c4d.DRAGTYPE_FILENAME_IMAGE)

        return True


# Define a global variable of the dialog to keep it alive in a Script Manager script. ASYNC dialogs
# should not be opened in production code from a Script Manager script, as this results in a
# dangling dialog. Implement a command plugin when you need async dialogs in production.
dlg: BitmapStackDialog = BitmapStackDialog()
if __name__ == "__main__":
    dlg.Open(dlgtype=c4d.DLG_TYPE_ASYNC, defaultw=150, defaulth=250)

Hi,

thanks for the kind words both from Maxon and the community. I am looking forward to my upcoming adventures with the SDK Team and Cinema community.

Cheers,
Ferdinand

Hello @holgerbiebrach,

please excuse the wait. So, this is possible in Python and quite easy to do. This new behavior is just the old dialog folding which has been reworked a little bit. I have provided a simple example at the end of the posting. There is one problem regarding title bars which is sort of an obstacle for plugin developers which want to distribute their plugins, it is explained in the example below.

I hope this helps and cheers,
Ferdinand

The result:

The code:

"""Example for a command plugin with a foldable dialog as provided with the
Asset Browser or Coordinate Manger in Cinema 4D R25.

The core of this is just the old GeDialog folding mechanic which has been
changed slightly with R25 as it will now also hide the title bar of a folded
dialog, i.e., the dialog will be hidden completely.

The structure shown here mimics relatively closely what the Coordinate Manger
does. There is however one caveat: Even our internal implementations do not
hide the title bar of a dialog when unfolded. Instead, this is done via 
layouts, i.e., by clicking onto the ≡ icon of the dialog and unchecking the
"Show Window Title" option and then saving such layout. If you would want
to provide a plugin which exactly mimics one of the folding managers, you
would have to either ask your users to take these steps or provide a layout.

Which is not ideal, but I currently do not see a sane way to hide the title
bar of a dialog. What you could do, is open the dialog as an async popup which 
would hide the title bar. But that would also remove the ability to dock the 
dialog. You could then invoke `GeDialog.AddGadegt(c4d.DIALOG_PIN, SOME_ID)`to 
manually add a pin back to your dialog, so that you can dock it. But that is 
not how it is done internally by us, as we simply rely on layouts for that.
"""

import c4d


class ExampleDialog (c4d.gui.GeDialog):
    """Example dialog that does nothing.

    The dialog itself has nothing to do with the implementation of the
    folding.
    """
    ID_GADGETS_START = 1000
    ID_GADGET_GROUP = 0
    ID_GADGET_LABEL = 1
    ID_GADGET_TEXT = 2

    GADGET_STRIDE = 10
    GADEGT_COUNT = 5

    def CreateLayout(self) -> bool:
        """Creates dummy gadgets.
        """
        self.SetTitle("ExampleDialog")
        flags = c4d.BFH_SCALEFIT

        for i in range(self.GADEGT_COUNT):
            gid = self.ID_GADGETS_START + i * self.GADGET_STRIDE
            name = f"Item {i}"

            self.GroupBegin(gid + self.ID_GADGET_GROUP, flags, cols=2)
            self.GroupBorderSpace(5, 5, 5, 5)
            self.GroupSpace(2, 2)
            self.AddStaticText(gid + self.ID_GADGET_LABEL, flags, name=name)
            self.AddEditText(gid + self.ID_GADGET_TEXT, flags)
            self.GroupEnd()
        return True


class FoldingManagerCommand (c4d.plugins.CommandData):
    """Provides the implementation for a command with a foldable dialog.
    """
    ID_PLUGIN = 1058525
    REF_DIALOG = None

    @property
    def Dialog(self) -> ExampleDialog:
        """Returns a class bound ExampleDialog instance.
        """
        if FoldingManagerCommand.REF_DIALOG is None:
            FoldingManagerCommand.REF_DIALOG = ExampleDialog()

        return FoldingManagerCommand.REF_DIALOG

    def Execute(self, doc: c4d.documents.BaseDocument) -> bool:
        """Folds or unfolds the dialog.

        The core of the folding logic as employed by the Asset Browser
        or the Coordinate manager in R25.
        """
        # Get the class bound dialog reference.
        dlg = self.Dialog
        # Fold the dialog, i.e., hide it if it is open and unfolded. In C++
        # you would also want to test for the dialog being visible with
        # GeDialog::IsVisible, but we cannot do that in Python.
        if dlg.IsOpen() and not dlg.GetFolding():
            dlg.SetFolding(True)
        # Open or unfold the dialog. The trick here is that calling
        # GeDialog::Open will also unfold the dialog.
        else:
            dlg.Open(c4d.DLG_TYPE_ASYNC, FoldingManagerCommand.ID_PLUGIN)

        return True

    def RestoreLayout(self, secret: any) -> bool:
        """Restores the dialog on layout changes.
        """
        return self.Dialog.Restore(FoldingManagerCommand.ID_PLUGIN, secret)

    def GetState(self, doc: c4d.documents.BaseDocument) -> int:
        """Sets the command icon state of the plugin.

        This is not required, but makes it a bit nicer, as it will indicate
        in the command icon when the dialog is folded and when not.
        """
        dlg = self.Dialog
        result = c4d.CMD_ENABLED
        if dlg.IsOpen() and not dlg.GetFolding():
            result |= c4d.CMD_VALUE

        return result


def RegisterFoldingManagerCommand() -> bool:
    """Registers the example.
    """
    return c4d.plugins.RegisterCommandPlugin(
        id=FoldingManagerCommand.ID_PLUGIN,
        str="FoldingManagerCommand",
        info=c4d.PLUGINFLAG_SMALLNODE,
        icon=None,
        help="FoldingManagerCommand",
        dat=FoldingManagerCommand())


if __name__ == '__main__':
    if not RegisterFoldingManagerCommand():
        raise RuntimeError(
            f"Failed to register {FoldingManagerCommand} plugin.")

Dear Community,

this question reached us via email-support in the context of C++, but I thought the answer might be interesting for other users too.

The underlying question in this case was how to project points from object or world space into the texture space of an object with UV data. I am showing here deliberately an approach that can be followed both in C++ and Python, so that all users can benefit from this. In C++ one has also the option of using VolumeData and its methods VolumeData::GetUvw or VolumeData::ProjectPoint but must then either implement a volume shader (as otherwise the volume data attached to the ChannelData passed to ShaderData::Output will be nullptr), or use VolumeData:: AttachVolumeDataFake to access ::ProjectPoint. There is however no inherent necessity to take this shader bound route as shown by the example.

Cheers,
Ferdinand

Result

The script has created a texture with red pixels for the intersection points of the rays cast from each vertex of the spline towards the origin of the polygon object. The script also created the null object rays to visualize the rays which have been cast.

raycast_texture.c4d : The scene file.

Code

You must save the script to disk before running it, as the script infers from the script location the place to save the generated texture to.

"""Demonstrates how to project points from world or object space to UV space.

This script assumes that the user has selected a polygon object and a spline object in the order
mentioned. The script projects the points of the spline object onto the polygon object and creates
a texture from the UV coordinates of the projected points. The texture is then applied to the
polygon object.

The script uses the `GeRayCollider` class to find the intersection of rays cast from the points of
the spline object to the polygon object. The UV coordinates of the intersection points are then
calculated using the `HairLibrary` class. In the C++ API, one should use maxon::
GeometryUtilsInterface::CalculatePolygonPointST() instead.

Finally, using GeRayCollider is only an example for projecting points onto the mesh. In practice,
any other method can be used as long as it provides points that lie in the plane(s) of a polygon.

The meat of the example is in the `main()` function. The other functions are just fluff.
"""

import os
import c4d
import mxutils
import uuid

from mxutils import CheckType

doc: c4d.documents.BaseDocument  # The currently active document.
op: c4d.BaseObject | None  # The primary selected object in `doc`. Can be `None`.

def CreateTexture(points: list[c4d.Vector], path: str, resolution: int = 1000) -> None:
    """Creates a texture from the given `points` and saves it to the given `path`.

    Parameters:
        path (str): The path to save the texture to.
        points (list[c4d.Vector]): The points to create the texture from.
    """
    # Check the input values for validity.
    if os.path.exists(path):
        raise FileExistsError(f"File already exists at path: {path}")
    if not path.endswith(".png"):
        raise ValueError("The path must end with '.png'.")

    # Create a drawing canvas to draw the points on.
    canvas: c4d.bitmaps.GeClipMap = CheckType(c4d.bitmaps.GeClipMap())
    if not canvas.Init(resolution, resolution, 24):
        raise MemoryError("Failed to initialize GeClipMap.")

    # Fill the canvas with white.
    canvas.BeginDraw()
    canvas.SetColor(255, 255, 255)
    canvas.FillRect(0, 0, resolution, resolution)

    # Draw the points on the canvas.
    canvas.SetColor(255, 0, 0)
    for p in points:
        x: int = int(p.x * resolution)
        y: int = int(p.y * resolution)
        x0: int = max(0, x - 1)
        y0: int = max(0, y - 1)
        x1: int = min(resolution, x + 1)
        y1: int = min(resolution, y + 1)
        canvas.FillRect(x0, y0, x1, y1)

    canvas.EndDraw()

    # Save the canvas to the given path.
    bitmap: c4d.bitmaps.BaseBitmap = CheckType(canvas.GetBitmap())
    bitmap.Save(path, c4d.FILTER_PNG)

    c4d.bitmaps.ShowBitmap(bitmap)

def ApplyTexture(obj: c4d.BaseObject, path: str) -> None:
    """Applies the texture at the given `path` to the given `obj`.
    """
    CheckType(obj, c4d.BaseObject)

    # Check the input values for validity.
    if not os.path.exists(path):
        raise FileNotFoundError(f"File does not exist at path: {path}")

    # Create a material and apply the texture to it.
    material: c4d.BaseMaterial = CheckType(c4d.BaseMaterial(c4d.Mmaterial), c4d.BaseMaterial)
    obj.GetDocument().InsertMaterial(material)

    shader: c4d.BaseShader = CheckType(c4d.BaseShader(c4d.Xbitmap), c4d.BaseShader)
    shader[c4d.BITMAPSHADER_FILENAME] = path
    material.InsertShader(shader)
    material[c4d.MATERIAL_COLOR_SHADER] = shader
    material[c4d.MATERIAL_PREVIEWSIZE] = c4d.MATERIAL_PREVIEWSIZE_1024

    # Apply the material to the object.
    tag: c4d.TextureTag = CheckType(obj.MakeTag(c4d.Ttexture))
    tag[c4d.TEXTURETAG_PROJECTION] = c4d.TEXTURETAG_PROJECTION_UVW
    tag[c4d.TEXTURETAG_MATERIAL] = material

def CreateDebugRays(spline: c4d.SplineObject, p: c4d.Vector) -> None:
    """Adds spline objects to the document to visualize the rays from the given `p` to the points of
    the given `spline`.
    """
    doc: c4d.documents.BaseDocument = CheckType(spline.GetDocument(), c4d.documents.BaseDocument)
    rays: c4d.BaseObject = c4d.BaseObject(c4d.Onull)
    rays.SetName("Rays")
    doc.InsertObject(rays)

    for q in spline.GetAllPoints():
        ray: c4d.SplineObject = c4d.SplineObject(2, c4d.SPLINETYPE_LINEAR)
        ray.SetPoint(0, p)
        ray.SetPoint(1, q * spline.GetMg())
        ray.Message(c4d.MSG_UPDATE)
        ray.InsertUnder(rays)

def main() -> None:
    """Carries out the main logic of the script.
    """
    # Check the object selection for being meaningful input.
    selected: list[c4d.BaseObject] = doc.GetActiveObjects(c4d.GETACTIVEOBJECTFLAGS_SELECTIONORDER)
    if (len(selected) != 2 or not selected[0].CheckType(c4d.Opolygon) or
        not selected[1].CheckType(c4d.Ospline)):
        raise ValueError("Please select a polygon object and a spline object.")

    polygonObject, splineObject = selected

    # Get the uvw tag, the points, and the polygons of the polygon object.
    uvwTag: c4d.UvwTag = mxutils.CheckType(polygonObject.GetTag(c4d.Tuvw))
    points: list[c4d.Vector] = [polygonObject.GetMg() * p for p in polygonObject.GetAllPoints()]
    polys: list[c4d.CPolygon] = polygonObject.GetAllPolygons()

    # We are casting here in a dumb manner towards the center of the polygon object. In practice,
    # one should cast rays towards the plane of the polygon object. Or even better, use another
    # method to project the points onto the polygon object, as GeRayCollider is not the most 
    # efficient thing in the world.
    rayTarget: c4d.Vector = polygonObject.GetMg().off
    CreateDebugRays(splineObject, rayTarget)

    # Initialize the GeRayCollider to find the intersection of rays cast from the points of the
    # spline object to the polygon object.
    collider: c4d.utils.GeRayCollider = c4d.utils.GeRayCollider()
    if not collider.Init(polygonObject):
        raise MemoryError("Failed to initialize GeRayCollider.")


    # Init our output list and iterate over the points of the spline object.
    uvPoints: list[c4d.Vector] = []
    for p in splineObject.GetAllPoints():

        # Transform the point from object to world space (q) and then to the polygon object's space
        # (ro). Our ray direction always points towards the center of the polygon object.
        q: c4d.Vector = splineObject.GetMg() * p
        ro: c4d.Vector = ~polygonObject.GetMg() * q
        rd: c4d.Vector = rayTarget - ro

        # Cast the ray and check if it intersects with the polygon object.
        if not collider.Intersect(ro, rd, 1E6) or collider.GetIntersectionCount() < 1:
            continue
        
        # Get the hit position and the polygon ID of the intersection.
        hit: dict = collider.GetNearestIntersection()
        pos: c4d.Vector = mxutils.CheckType(hit.get("hitpos", None), c4d.Vector)
        pid: int = mxutils.CheckType(hit.get("face_id", None), int)

        # One mistake would be now to use the barycentric coordinates that are in the intersection
        # data, as Cinema uses an optimized algorithm to interpolate in a quad and not the standard
        # cartesian-barycentric conversion. In Python these polygon weights are only exposed in a 
        # bit weird place, the hair library. In C++ these barycentric coordinates make sense because
        # there exist methods to convert them to weights. In Python the barycentric coordinates are
        # pretty much useless as we do not have such a conversion function here.

        # Compute the weights s, t for the intersection point in the polygon.
        s, t = c4d.modules.hair.HairLibrary().GetPolyPointST(
            pos, points[polys[pid].a], points[polys[pid].b],
                 points[polys[pid].c], points[polys[pid].d], True)

        # Get the uv polygon and bilinearly interpolate the coordinates using the weights. It would
        # be better to use the more low-level variable tag data access functions in VariableTag 
        # than UvwTag.GetSlow() in a real-world scenario.
        uvw: list[c4d.Vector] = list(uvwTag.GetSlow(pid).values())
        t0: c4d.Vector = c4d.utils.MixVec(uvw[0], uvw[1], s)
        t1: c4d.Vector = c4d.utils.MixVec(uvw[3], uvw[2], s)
        uv: c4d.Vector = c4d.utils.MixVec(t0, t1, t)

        # Append the UV coordinates to the output list.
        uvPoints.append(uv)

    # Write the UV coordinates to a texture and apply it to the polygon object.
    path: str = os.path.join(os.path.dirname(__file__), f"image-{uuid.uuid4()}.png")
    CreateTexture(uvPoints, path, resolution=1024)
    ApplyTexture(polygonObject, path)

    c4d.EventAdd()


if __name__ == '__main__':
    main()

Hi,

that your script is not working has not anything to do with pseudo decimals, but the fact that you are treating numbers as strings (which is generally a bad idea) in a not very careful manner. When you truncate the string representation of a number which is represented in scientific notation (with an exponent), then you also truncate that exponent and therefor change the value of the number.

To truncate a float you can either take the floor of my_float * 10 ** digits and then divide by 10 ** digits again or use the keyword round.

data = [0.03659665587738824,
        0.00018878623163019122,
        1.1076812650509394e-03,
        1.3882258325566638e-06]

for n in data:
    rounded = round(n, 4)
    floored = int(n * 10000) / 10000
    print(n, rounded, floored)

0.03659665587738824 0.0366 0.0365
0.00018878623163019122 0.0002 0.0001
0.0011076812650509394 0.0011 0.0011
1.3882258325566637e-06 0.0 0.0
[Finished in 0.1s]

Cheers
zipit

Dear community,

We will have to touch multiple parts of developers.maxon.net on the 18.01.2024 and 19.01.2024 22.01.2024. This will result in outages of our documentation and the forum these days. I will try to keep the outage times to a minimum and it will certainly not span the whole two days. But especially one task I will do on Friday might take hours to complete and I can only do that on a forum which is in maintenance mode.

Please make sure to download a recent offline documentation in case you plan to do extended development work the next two days. As a result, forum support might also be delayed on these days.

Cheers,
Ferdinand

Hi,

as @Cairyn said the problem is unreachable code. I also just saw now that you did assign the same ID to all your buttons in your CreateLayout(). Ressource and dialog element IDs should be unique. I would generally recommend to define your dialogs using a resource, but here is an example on how to do it in code.

BUTTON_BASE_ID = 1000
BUTTON_NAMES = ["Button1", "Button2", "Button3", "Button4", "Button5"]
BUTTON_DATA = {BUTTON_BASE_ID + i: name for i, name in enumerate(BUTTON_NAMES)}

class MyDialog(gui.GeDialog):

    def CreateLayout(self):
        """
        """
        self.GroupBegin(id=1013, flags=c4d.BFH_SCALEFIT, cols=5, rows=4)
        for element_id, element_name in BUTTON_DATA.items():
            self.AddButton(element_id, c4d.BFV_MASK, initw=100, 
                           name=element_name)
        self.GroupEnd()
        return True

    def Command(self, id, msg):
        """
        """
        if id == BUTTON_BASE_ID:
            print "First button has been clicked"
        elif id == BUTTON_BASE_ID + 1:
            print "Second button has been clicked"
        # ...
        if id in BUTTON_DATA.keys(): # or just if id in BUTTON_DATA
            self.Close()
        return True

Dear development community,

On September the 10th, 2024, Maxon Computer released Cinema 4D 2025.0.0. For an overview of the new features of Cinema 4D 2025.0, please refer to the release announcement. Alongside this release, a new Cinema 4D SDK and SDK documentation have been released, reflecting the API changes for 2025.0.0. The major changes are:

C++ API

• What was formerly has been know as the Classic API has been deprecated in favour of the Cinema API. Alongside this a new cinema namespace has been introduced which contains all the entities which were formerly in the anonymous global namespace known as the Classic API. Plugin authors must adopt their code to this new API, although the changes are not nearly as extensive as for 2024. See the 2025 migration guide for details. Code examples and documentation have been updated to now refer to a Cinema API.
• 2025 uses OCIO as the default color management mode, brings an improved color picker, and made general improvements to the consistency of the OCIO implementation. This had some effects on the underlying OCIO API which are reflected in two new code examples in the OCIO Manual and a new plugin in the SDK.

Python API

• Python also received the update from Classic to Cinema API. But here the change was more of a cosmetic nature confined to the documentation. The c4d package remains the home for all formerly Classic and now Cinema API entities.
• The mxutils package received updates around standardized scene traversal, random number generation, and more.
• Graph descriptions now support variadic ports of arbitrary complexity and explicit port references.

Head to our download section for the newest SDK downloads, or the C++ and Python API change notes for an in detail overview of the changes.

We discovered late in the cycle bugs in the Asset API code examples and OCIO code in the Python SDK. Which is why the publication of the Python SDK and GitHub code examples has been postponed until these bugs are fixed. They should be ready latest by Friday the 13th of September. But the Python online documentation is accessible and error free (to our knowledge).

We had to make some last minute changes to the C++ SDK regarding OCIO code examples. Only the extended C++ SDK contains these changes. The application provided sdk.zip will catch up with the next release of Cinema 4D.

Happy rendering and coding,
the Maxon SDK Team

Cloudflare unfortunately still does interfere with our server cache. And you might have to refresh your cache manually.

When you are not automatically redirected to the new versions, and also do not see 2024.5 in the version selector, please press CTRL + F5 or press CTRL and click on the reload icon of your browser anywhere on developers.maxon.net/docs/ to refresh your cache. You only have to do this once and it will apply to all documentations at once. Otherwise your cache will automatically update latest by 19/07/2024 00:00.

Hi,

sorry for all the confusion. You have to pass actual instances of objects. The following code does what you want (and this time I actually tried it myself ;)).

import c4d

def main():
    """
    """
    bc = doc.GetAllTextures(ar=doc.GetMaterials())
    for cid, value in bc:
        print cid, value

if __name__=='__main__':
   main()

Cheers,
zipit

Dear development community,

On June the 18th, 2025, Maxon Computer released Cinema 4D 2025.3.0. For an overview of the new features of Cinema 4D 2025.3.0, please refer to the 2025.3.0 release notes. Alongside this release, a new Cinema 4D SDK and SDK documentation have been released, reflecting the API changes for 2025.3.0. The major changes are:

C++ API

• After the introduction of the CMake build system generator in Cinema 4D 2025.2.0, the C++ SDK now only supports CMake as its build system generator. The Legacy Build System is no longer supported. When you have not yet switched to CMake, please refer to our Build Systems manual for more information on how to switch to CMake.
• Updated the required Windows SDK version to Windows 10 SDK 10.0.20348.0. You might have to update Visual Studio and install the SDK via the Visual Studio installer app.

Python API

In 2025.3.0, there is a critical issue with c4dpy that will cause it to halt indefinitely when run for the first time. See the c4dpy manual for an explanation and workaround. This issue will be fixed with a hotfix for 2025.3.0.

• Added features to c4d.documents.BatchRender class, to have more control over render settings, cameras, and takes for a given job.
• Added a suite of new code examples around the subject of dialogs, including both simple beginner examples, as well as more complex examples covering subjects such as dynamic GUIs, value and layout persistence, and using resources to define dialogs and string translations. The new examples all begin with the prefix py-cmd_gui_, see our plugin examples overview for details.

Head to our download section to grab the newest SDK downloads, or read the C++ or Python API change notes for an in detail overview of the changes.

Happy rendering and coding,
the Maxon SDK Team

Cloudflare unfortunately still does interfere with our server cache. You might have to refresh your cache manually to see new data when you read this posting within 24 hours of its release.

Hey @lasselauch,

I tried your plugin in 2025.3.1 (Build 2025_3_1_dec42f629989_1872501510) Win and 2025.3.0 (Build 2025_3_0_dd53fd5fe589_1867889325) OSX (closest version I got on my Mac) with a student license and it just loads fine.

GUI Operations in Boot Phase

I noticed that you are creating dialogs and doing file operations while Cinema 4D is booting (i.e., likely within the __name__ == '__main__' context guard of your pyp file). That is absolutely not allowed.

The registration phase is for registering hooks only. Installing, querying web servers, opening fancy dialogs or doing other shenanigans is absolutely not allowed and can very well lead to malfunctions or crashes. For Python plugins this is less severe as for C++ plugins as Python plugins live in their own fake boot bubble and most systems should have been brought up at this point, but you are still poking the bear.

We had not too long ago a similar case but for license validation. Register your plugin hook(s) in the boot phase and nothing else. When you have some simple serial or other logic as shown in the serial example, you can run it also, everything else must be done later. Then once Cinema 4D has fully booted (c4d. C4DPL_STARTACTIVITY has been emitted) or when the user tries to use your plugin, you can do a complex license check using web servers or install dependencies. You can then force a restart with c4d.RestartMe.This could absolutely be the cause for the issues of the user and it working on most systems does not mean anything.

Fig. I: Doing GUI and file operations while Cinema 4D is loading: this is really bad!

Nested Plugin Package

Your download package creates a nested folder, which sort of sets a trap for less experienced users, as linking the outer folder will cause the plugin not to load (due to the limitation of how Python plugins are discovered compared to C++ plugins). I would recommend a flat structure.

TLDR: I would bet money on the user having linked the wrong folder.

Cheers,
Ferdinand

edit:

And just for completeness, here is your plugin loaded from {c4d}/plugins.

Hey @BigRoy,

Thank you for reaching out to us and your question. We do not allow for topics that are a collection of questions from one user. New questions mandate new topics, unless they are clear follow up questions on an existing topic. The reason for this is so that this forum remains a searchable database.

Please create new topics on your own in the future. I have forked your topic.

Your topic is also lacking an actual question. Here I can infer your question, but for more complex subjects I might not be able to. It is important to have a literal question close to the start of your topic. See Support Procedures: How to Ask Questions and the examples below for what makes a good technical question.

From the context I am assuming here the question is:

Is there an API function that returns the full physical file path of a rendered file for a given render setting and in particular the Save > Name format?

The answer is unfortunately that no such function exists. When you need this feature, you have to hard code it yourself.

Cheers,
Ferdinand

Hey @lasselauch,

Thank you for reaching out to us. In general, we do not regulate users of EDU licenses being able to load plugins or not. The screenshot you sent us just tells the user you cannot manually mount the path {c4d}/plugins as it is an auto-mounted plugin search path. With 2025 we added some minor sanity checks for how plugin paths can be added, so that users cannot 'double dip' the same plugin path and with that cause conflicts.

So, when the user created a path {c4d}/plugins, the plugin should simply load from there, no adding as a plugin path required. You can send me your plugin, and I can see if I can load it in an EDU. It is hard to tell with this little information what is going on and where the fault lies.

In {c4d}/plugins you usually do not have write permissions, so when your plugin tries to write to its own root path, that could be an issue. Or the user did not check the console properly and your plugin actually writes something to the console or throws an error. It could of course also be that there is a bug in Cinema 4D.

I would ask the user:

1 - What is the content of the Plugin Manager (does your plugin show up)?
2 - Ask for a screenshot of a scrolled down Python console.
3 - Common mistake are also over-nested plugins. When you have your plugin as:

foo/
└── bar/
    └── my_plugin/
        ├── res/
        └── my_plugin.pyp

mounting /foo/bar/ as a plugin search path will load your Python plugin, mounting foo will not.

Cheers,
Ferdinand

Hey @ECHekman,

Thank you for your question. This is a tricky one. When NodeData::Read is emitted, Cinema 4D is currently reading a file and in the process of deserializing your node; so it indeed is not yet 'fully instantiated', as that is the whole point of the method. You are here not meant to manipulate the scene graph (the node is not yet attached), but read and store data on your plugin hook. I.e., you are supposed to do something with your MyMaterialData and not the GeListNode/BaseMaterial which is being passed in as the first argument of Read.

The common workflow is to read data from the HyperFile which is passed in and store it on your NodeData instance. Passed in is also the important version number (which is called for some odd reason disklevel) of your HyperFile container.

As always, you are bound to the main thread for scene graph manipulations. So, NodeData::Init is not a good candidate when wanting to poke around in the scene graph, as it can be called off main thread and on dettached dummy nodes. A good approach is to hook into NodeData::Message and listen for MSG_DOCUMENTINFO to catch a document just having been loaded. This is for your specific case of wanting to manipulate nodes which have been deserialized. If you want to manipulate node instantiation, MSG_MENUPREPARE is a god choice. But it is only called for nodes which have been instantiated from direct user interactions such as a menu click. So, MSG_MENUPREPARE is not being emitted for nodes loaded from a file.

The drill to do what you want to do would be:

1. [optional] Overwrite NodeData::Read/Write/CopyTo to read, write, and copy custom data, and possibly use/detect different disk levels to catch different versions of a node type being loaded. You would have to match this with incrementing the disk level in your RegisterMaterialPlugin call, so that there are old and new versions of your material type out there.
2. Hook into the document being loaded, check the scene state, and possible data left behind for you by NodeData::Read and ::Init.
3. Manipulate the scene graph to your liking.

Cheers,
Ferdinand

Hey, almost forgot: We have fixed this, an upcoming release will contain the fix . We, however, went with a fix removing the offending call instead of fixing the incorrect progress handler method (which was the issue).

So, in other words: The workaround I showed here won't work in future versions, as the number of progress calls will be halved. Before one got two calls per update when rendering with the preview renderer: One for the correctly working image progress update and one for the buggy generic progress update. We have removed the latter.

Halving the number of calls is more technically correct, since it made no sense to call the progress hook twice per update but will break any plugins that relied on that incorrect behaviour.

Cheers,
Ferdinand

Hey Bruce, multiple people in your company have access. When you do not, reach out to us, so that we can set you up.

Hey,

so, I actually did get it right, I apparently just did not check properly when I tested the common case of second level IDs of dynamic properties starting off at 1000.

Cheers,
Ferdinand

"""Demonstrates how to set values on dynamic input ports of a Condition node in an XPresso tag.
"""

import c4d

from c4d.modules.graphview import GvNodeMaster, GvNode, GvPort, XPressoTag
from mxutils import CheckType

doc: c4d.documents.BaseDocument  # The currently active document.
op: c4d.BaseObject | None  # The primary selected object in `doc`. Can be `None`.


def main() -> None:
    """Called by Cinema 4D when the script is being executed.
    """
    # Create a new XPresso tag with a Condition node.
    null: c4d.BaseObject = CheckType(c4d.BaseObject(c4d.Onull))
    tag: XPressoTag = CheckType(null.MakeTag(c4d.Texpresso))
    master: GvNodeMaster = CheckType(tag.GetNodeMaster())
    doc.InsertObject(null)

    root: GvNode = CheckType(master.GetRoot())
    condNode: GvNode = CheckType(master.CreateNode(root, c4d.ID_OPERATOR_CONDITION, x=200, y=200))

    # Count the number of input ports on the Condition node. For our case, a freshly instantiated
    # node we do not really have to do this, since there will always be static "Switch" port and
    # two dynamic input ports. But when we are working on an existing graph, we have to count the
    # ports to know how many dynamic ports there are.
    inputPorts: list[GvPort] = condNode.GetInPorts()
    portCount: int = len(inputPorts)

    # There is no predefined symbol for this, the implementation counts just ports, so dynamic ports
    # start at 1001 because the input port GV_CONDITION_SWITCH has the ID 1000.
    idDynamicStart: int = 1001

    # Iterate over all dynamic input ports (-1 -> skipping the first static "Switch" port).
    for i in range(portCount - 1): 
        # Define the DescID for the dynamic input port.
        did: c4d.DescID = c4d.DescID(
            # The first desc level for variadic/dynamic ports is always a sub container. For a 
            # condition node where the variadic ports can only be inputs and always are of one type,
            # this is GV_CONDITION_INPUT. Other nodes which can have variadic ports of different 
            # types (like the Python node) have different sub container IDs for inputs and outputs, 
            # e.g., IN_REAL for all real inputs, IN_STRING for all string inputs, OUT_LONG for all 
            # long outputs, etc.
            c4d.DescLevel(c4d.GV_CONDITION_INPUT, c4d.DTYPE_SUBCONTAINER, condNode.GetType()),
            # And the second desc level is the dynamic port ID, starting at 1001 for the first dynamic
            # input port, 1002 for the second dynamic input port, and so on. It unfortunately not very
            # standardized, where these start.
            c4d.DescLevel(idDynamicStart + i, c4d.DTYPE_REAL, 0)
        )
        # Set the value of the dynamic input port to some float value.
        result: bool = condNode.SetParameter(did, float((i + 1) * 10), c4d.DESCFLAGS_SET_0)
        if not result:
            print("Failed to set value on port index:", i)

    # Or another common workflow, we want to set a dynamic port by port label (instead of knowing
    # the index in advance).

    # Find the first port that starts with "Input".
    targetLabel: str = "Input"
    targetPort: GvPort | None = next((port for port in inputPorts 
                                      if port.GetName(condNode).startswith(targetLabel)), None)
    
    # We found a port with that label.
    if targetPort is not None:
        # Unlike in the Nodes API, we cannot set the value on a port directly, we always have to go
        # through the node and use a DescID to identify the port. So we must find the index of the 
        # port in the input ports list to calculate the dynamic port ID.
        index: int = inputPorts.index(targetPort)
        result: bool = condNode.SetParameter(
            c4d.DescID(
                c4d.DescLevel(c4d.GV_CONDITION_INPUT, c4d.DTYPE_SUBCONTAINER, condNode.GetType()),
                c4d.DescLevel(idDynamicStart + (index - 1), c4d.DTYPE_REAL, 0)
            ),
            99.9, # Set the value to 99.9
            c4d.DESCFLAGS_SET_0
        )
        if not result:
            print("Failed to set value on port:", targetPort.GetName(condNode))

    c4d.EventAdd()

if __name__ == '__main__':
    main()

FYI: The RS team just told me that they agree that this is a bug and that they will fix this. Please reach out via our beta forums for details.

So, the code I showed you has an expiration date.

Hey @BruceC,

Thank you for your question. I just checked, and what RS calls the index ratio does not really have much to do with indices and is instead based on the uvw coordinate of a particle. This might be a bug, but you would have to talk with the Redshift team for that. Anyway, find below some Python code to emulate computing that 'index ratio'.

Cheers,
Ferdinand

Result

I emulated your setup:

Code

import c4d
import mxutils

doc: c4d.documents.BaseDocument  # The currently active document.
op: c4d.BaseObject | None  # The primary selected object in `doc`. Can be `None`.


def main() -> None:
    """Called by Cinema 4D when the script is being executed.
    """
    data: c4d.modules.mograph.MoData = mxutils.CheckType(c4d.modules.mograph.GeGetMoData(op))
    uvw: list[c4d.Matrix] = data.GetArray(c4d.MODATA_UVW)
    for i in range(data.GetCount()):
        # That is how the 'index ratio' is computed, it is effectively just the shifted x-component
        # of the uvw coordinate of the particle. The color is then just (ratio, ratio, ratio). Not very
        # 'indexy'.
        ratio: float = 1 - uvw[i].x
        print(f"{i}: {ratio}")

if __name__ == '__main__':
    main()

Hey @ECHekman,

it depends a bit on what you do in your description, which bases you include, and what you consider NodeData instances in your case. Are you actually talking about plain NodeData hooks or are you talking about derived types such as ObjectData?

When we look for example into Ocube.res, we can see it includes Obase:

CONTAINER Ocube
{
	NAME Ocube;
	INCLUDE Obase;  // includes the description base for all objects Obase.res

Which among other things contains the Obaselist group, which is the group you mean.

You could either not include the base description for your node type, or use a modified base which for example hides all elements in that group. But I personally would say that none of these approaches are really a good idea, as Cinema 4D is designed with the assumption that each basic scene element (object, tag, etc.) includes their base description.

Falling to do so, will either make your plugin outright not work, or - when using more 'clever' approaches such as hiding all parameters, or hiding the whole group via GetDDescription or a modified base - severely impact how users can interact with your scene element.

When you implement a plain NodeData hook, you should not see any extra tabs, as plain node hooks should not include any bases.

Cheers,
Ferdinand