Getting Started: Scene Elements

Table of Contents

• Overview
• Working with Documents
• Creating new Objects
• Setting Parameters
• Creating new Materials
• Working with Tags
• Finding Elements in the Document
• Creating Polygon Objects
• Rendering

Overview

• A 3D scene is represented by a BaseDocument.
• The "active" BaseDocument is currently displayed in the Cinema 4D viewport. Other BaseDocument instances can be allocated at any time.
• Cinema 4D must be informed on any change to the "active" BaseDocument by calling EventAdd().
• 3D objects are based on BaseObject and can be inserted into a BaseDocument.
• Tags add additional functionality or data to a BaseObjects. Tags are based on BaseTag.
• Polygon data is represented as PolygonObject objects.
• Materials are based on BaseMaterial. The standard material is represented as Material.
• A given BaseDocumnet can be rendered using the RenderDocument() function.

Working with Documents

A 3D scene is represented as a BaseDocument. A BaseDocument can store objects, materials, takes etc. Cinema 4D can handle multiple documents at once. The document display in the viewport is the active document that can be accessed with GetActiveDocument(). This active document must only be modified in the context of user interaction from the main thread. It must not be edited from within the execution pipeline or from a thread that is not the main thread.

After the active document has been edited, one must call EventAdd() to inform Cinema 4D that something has changed.

See also

• BaseDocument Manual
• Core Messages Manual

  // This example creates a new BaseDocument and inserts it
  // into the application as the currently active document.
 
  // create a new document
  BaseDocument* const newDoc = BaseDocument::Alloc();
  if (newDoc == nullptr)
    return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
 
  // insert document into list of documents
  InsertBaseDocument(newDoc);
  // make document the active document
  SetActiveDocument(newDoc);
 
  // set name
  newDoc->SetDocumentName("new_document.c4d");
 
  // update Cinema 4D
  EventAdd();

Creating new Objects

BaseObject is the base class of all scene objects. Such scene objects can be polygon objects or splines but also generators, deformers, camera objects or lights.

To create a new object one must know the object type's ID. E.g. the ID for a "Cube" is Ocube. A newly created object can simply be inserted into a BaseDocument that will take ownership.

See also Scene Elements Overview.

  // This example creates a new "Cube" object and
  // inserts it into the given BaseDocument.
 
  // create a new cube object
  BaseObject* const cube = BaseObject::Alloc(Ocube);
  if (cube == nullptr)
    return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
 
  // insert object into the BaseDocument
  doc->InsertObject(cube, nullptr, nullptr);

Setting Parameters

The BaseObject class is based on C4DAtom. This means that parameters of objects can be accessed using C4DAtom::SetParameter() and C4DAtom::GetParameter().

For each element type, there is typically a header file that includes the parameter IDs. E.g. for the Ocube object type there is the ocube.h header file.

Different objects are based on fundamental base classes. Ocube is based on Obase so it inherits the base class' parameters which are defined in the corresponding header file (e.g. obase.h).

See C4DAtom Manual.

  // This example changes the name and the size of the given object.
  // The ID PRIM_CUBE_LEN is defined in ocube.h
 
  // set new object name
  cube->SetName("This is a new Cube."_s);
 
  // set size
  const Vector size { 500, 500, 500 };
  const DescID sizeID = ConstDescID(DescLevel(PRIM_CUBE_LEN));
  cube->SetParameter(sizeID, size, DESCFLAGS_SET::NONE);

Creating new Materials

Materials and shaders can be created like objects. Materials must be inserted into the host BaseDocument. A new shader instance must be inserted into a host object. This is typically the material using the shader. BaseMaterial is the base class of all materials. Material is the class representing the standard Cinema 4D material.

See Materials and Shaders Overview.

  // This example creates a new material and a new shader for that material.
 
  // create a new material
  Material* const material = Material::Alloc();
  if (material == nullptr)
    return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
 
  // insert material into the BaseDocument
  doc->InsertMaterial(material);
 
  // create a new shader
  BaseShader* const noiseShader = BaseShader::Alloc(Xnoise);
  if (noiseShader == nullptr)
    return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
 
  // insert shader into the material
  material->InsertShader(noiseShader);
 
  // use shader in the "Color" channel
  const DescID shaderParameterID = ConstDescID(DescLevel(MATERIAL_COLOR_SHADER));
  material->SetParameter(shaderParameterID, noiseShader, DESCFLAGS_SET::NONE);

Working with Tags

Tags are used to add arbitrary data or additional functionality to given BaseObject. Tags that store information are e.g. NormalTag or UVWTag. A TextureTag is used to assign a material to a BaseObject.

See BaseTag and VariableTag Manual and TextureTag Manual.

  // This example creates a new TextureTag and assigns it to the given object.
 
  // create texture tag
  BaseTag* const textureTag = BaseTag::Alloc(Ttexture);
  if (textureTag == nullptr)
    return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
 
  // assing tag to object
  cube->InsertTag(textureTag);
 
  // assing material
  const DescID materialParameterID = ConstDescID(DescLevel(TEXTURETAG_MATERIAL));
  textureTag->SetParameter(materialParameterID, material, DESCFLAGS_SET::NONE);
 
  // set projection
  const DescID projectionParameterID = ConstDescID(DescLevel(TEXTURETAG_PROJECTION));
  textureTag->SetParameter(projectionParameterID, TEXTURETAG_PROJECTION_UVW, DESCFLAGS_SET::NONE);

Finding Elements in the Document

There are many different ways to access the objects, materials or tags that are stored in a BaseDocument. The user can select objects, materials and tags. The BaseDocument class gives access to these "active" elements. Additionally it is also possible to search for objects by name.

The objects of a scene are organized in a tree. For iterating such a tree see Navigation in Lists and Trees.

See BaseDocument Manual.

  // This example accesses the currently active object
  // and loops over the object's tags. It also loops over
  // the materials in the scene.
 
  // get the active object
  BaseObject* const activeObject = doc->GetActiveObject();
  if (activeObject != nullptr)
  {
    // print the object name
    const String name = activeObject->GetName();
    ApplicationOutput("Active Object: " + name);
 
    // print the name of all tags
    BaseTag* tag = activeObject->GetFirstTag();
 
    while (tag != nullptr)
    {
      const String tagName = tag->GetName();
      ApplicationOutput("Tag: " + tagName);
      tag = tag->GetNext();
    }
  }
 
  // print the name of all materials
 
  BaseMaterial* material = doc->GetFirstMaterial();
 
  while (material != nullptr)
  {
    const String materialName = material->GetName();
    ApplicationOutput("Material: " + materialName);
    material = material->GetNext();
  }

Creating Polygon Objects

A PolygonObject stores point and polygon data. Such a PolygonObject is created and inserted into the BaseDocument like any other object.

  // This example creates a new polygon object.
 
  // define point and polygon count
  const Int32 pointCnt = 4;
  const Int32 polyCnt  = 1;
 
  // create polygon object
  PolygonObject* const polygonObject = PolygonObject::Alloc(pointCnt, polyCnt);
  if (polygonObject == nullptr)
    return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
 
  // insert object into the document
  doc->InsertObject(polygonObject, nullptr, nullptr);
 
  // accees point and polygon data
  Vector*   const points = polygonObject->GetPointW();
  CPolygon* const polygons = polygonObject->GetPolygonW();
 
  const Bool pointsReady = points != nullptr;
  const Bool polygonsReady = polygons != nullptr;
 
  if (pointsReady && polygonsReady)
  {
    // set points
    points[0] = Vector(0, 0, 0);
    points[1] = Vector(0, 0, 100);
    points[2] = Vector(100, 0, 100);
    points[3] = Vector(100, 0, 0);
 
    // set polygon
    polygons[0] = CPolygon(0, 1, 2, 3);
 
    // inform the polygon object that internal data changed
    polygonObject->Message(MSG_UPDATE);
  }
  else
  {
    return maxon::UnexpectedError(MAXON_SOURCE_LOCATION);
  }

Rendering

The function RenderDocument() can be used to render a given BaseDocument.

  // This example creates a BaseBitmap to render the given document using RenderDocument().
 
  // prepare bitmap
  AutoAlloc<BaseBitmap> bitmap;
  if (bitmap == nullptr)
    return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
 
  const Int32 width  = 1280;
  const Int32 height = 720;
 
  const IMAGERESULT imageRes = bitmap->Init(width, height);
  if (imageRes != IMAGERESULT::OK)
    return maxon::UnexpectedError(MAXON_SOURCE_LOCATION);
 
  // define render settings
  RenderData* const rdata = doc->GetActiveRenderData();
  if (rdata == nullptr)
    return maxon::UnexpectedError(MAXON_SOURCE_LOCATION);
 
  BaseContainer renderSettings = rdata->GetDataInstanceRef();
  renderSettings.SetFloat(RDATA_XRES, width);
  renderSettings.SetFloat(RDATA_YRES, height);
 
  // render the document
  const RENDERFLAGS  flags = RENDERFLAGS::NODOCUMENTCLONE;
  const RENDERRESULT res = RenderDocument(doc, renderSettings,
    nullptr, nullptr, bitmap, flags, nullptr);
 
  if (res != RENDERRESULT::OK)
    return maxon::UnknownError(MAXON_SOURCE_LOCATION);
 
  // show result
  ShowBitmap(bitmap);