Hello @Dimitris_Derm.,
Welcome to the Maxon developers forum and its community, it is great to have you with us!
Getting Started
Before creating your next postings, we would recommend making yourself accustomed with our forum and support procedures. You did not do anything wrong, we point all new users to these rules.
- Forum Overview: Provides a broad overview of the fundamental structure and rules of this forum, such as the purpose of the different sub-forums or the fact that we will ban users who engage in hate speech or harassment.
- Support Procedures: Provides a more in detail overview of how we provide technical support for APIs here. This topic will tell you how to ask good questions and limits of our technical support.
- Forum Features: Provides an overview of the technical features of this forum, such as Markdown markup or file uploads.
It is strongly recommended to read the first two topics carefully, especially the section Support Procedures: How to Ask Questions.
About your First Question
I am not quite sure how your question is meant, but the loop and ring selection tools are accessible in the API. When you are literally asking for the algorithm, we cannot share that, as declared in our Support Procedures:
We will not reveal non-public functionalities of our APIs.
When you just want to use the tools programmatically, SendModelingCommand is the way to go. We also have a dedicated section in our examples for them.
Cheers,
Ferdinand
Result
Code
"""Demonstrates how to use the loop selection command in the Python API.
The script creates a cylinder, makes it editable, and then performs a loop selection based on two
vertices and a polygon index. Finally, it inserts the modified object into the active document and
updates the scene.
"""
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.
"""
# Instantiate a cylinder and insert it into a temporary working document.
cylinder: c4d.BaseObject = mxutils.CheckType(c4d.BaseObject(c4d.Ocylinder))
temp: c4d.documents.BaseDocument = mxutils.CheckType(c4d.documents.BaseDocument())
temp.InsertObject(cylinder)
# Make the object editable. We could also build the caches and get the cache, but since the
# subject is here SMC, we can also use SendModelingCommand and MODELINGCOMMAND_MAKEEDITABLE.
res: list[c4d.BaseObject] | bool = c4d.utils.SendModelingCommand(
c4d.MCOMMAND_MAKEEDITABLE, list=[cylinder], mode=c4d.MODELINGCOMMANDMODE_ALL, doc=temp)
if not res:
raise RuntimeError("Failed to make object editable.")
# The cylinder is now editable.
cylinder: c4d.PolygonObject = res[0]
# Now we are going to do the loop selection. These are the IDs defined in toolloopselection.h:
# MDATA_LOOP_SEL_STOP_AT_SELECTIONS = 1100, // BOOL
# MDATA_LOOP_SEL_STOP_AT_NON_QUADS = 1110, // BOOL
# MDATA_LOOP_SEL_STOP_AT_POLES = 1120, // BOOL
# MDATA_LOOP_FIRST_VERTEX = 1130, // LONG
# MDATA_LOOP_SECOND_VERTEX = 1131, // LONG
# MDATA_LOOP_POLYGON_INDEX = 1132, // LONG
# MDATA_LOOP_BOTH_SIDES = 1133, // BOOL
# MDATA_LOOP_SWAP_SIDES = 1134, // BOOL
# MDATA_LOOP_SELECTION_TYPE = 1140, // LONG (must be SELECTION_NEW, SELECTION_ADD or SELECTION_SUB)
# MDATA_LOOP_SEL_POLYGON_OBJECT = 1150, // LINK
settings: c4d.BaseContainer = c4d.BaseContainer()
# Define the major input, two vertices and a polygon index. You need all three, regardless of the output mode
# you choose in SMC.
settings[c4d.MDATA_LOOP_FIRST_VERTEX] = 2
settings[c4d.MDATA_LOOP_SECOND_VERTEX] = 3
settings[c4d.MDATA_LOOP_POLYGON_INDEX] = 1
# Define the selection mode, this is more cosmetic, as SELECTION_NEW is the default.
settings[c4d.MDATA_LOOP_SELECTION_TYPE] = c4d.SELECTION_NEW
# Carry out the loop selection, targeting edge mode.
res: list[c4d.BaseObject] | bool = c4d.utils.SendModelingCommand(
c4d.ID_MODELING_LOOP_TOOL, list=[cylinder], mode=c4d.MODELINGCOMMANDMODE_EDGESELECTION, bc=settings, doc=temp)
if not res:
raise RuntimeError("Failed to perform loop selection.")
# Scene elements can only be inserted once, the Python API removes nodes automatically when you call InsertObject, but
# C++ does not and there is no guarantee that the Python API babysits you in all cases where you can insert something,
# so it is good practice to ensure scene integrity yourself. (#cylinder is currently part of #temp).
cylinder.Remove()
# Insert the object into our scene, enable edge mode, make the object selected, and push an update event.
doc.InsertObject(cylinder)
doc.SetMode(c4d.Medges)
doc.SetActiveObject(cylinder)
c4d.EventAdd()
if __name__ == '__main__':
main()
