Let’s look at a simple example: the classic “Red Cone.” First we will look at the file format to see how the various nodes and fields fit together.

Later we will look at the code that creates this hierarchy (although you can probably deduce most of that from your Open Inventor experience).

Here is the traditional Open Inventor scene graph to display a red cone:

#Inventor V2.1 ascii
  Separator
    {
    Material { diffuseColor 1 0 0 }
    Cone {}
    }

#VRML V2.0 utf8
    Transform { 
        children Shape { 
            appearance Appearance { 
                material Material { diffuseColor 1 0 0 } 
            } 
            geometry Cone {} 
        }
    }

#X3D V3.0 utf8
    Transform { 
        children Shape { 
            appearance Appearance { 
                material Material { diffuseColor 1 0 0 } 
            } 
            geometry Cone {} 
        }
    }

For these nodes, the file is exactly the same as the VRML97 file except for the header. For a few nodes, there will be differences between the VRML97 and X3D file formats.

// VRML nodes
SoVRMLTransform *pRoot = new SoVRMLTransform;
SoVRMLShape *pShape = new SoVRMLShape;
SoVRMLAppearance *pApp = new SoVRMLAppearance;
SoVRMLMaterial *pMat = new SoVRMLMaterial;

pMat->diffuseColor.setValue(1, 0, 0);
pApp->material.setValue(pMat);
pShape->appearance.setValue(pApp);
pShape->geometry.setValue(new SoVRMLCone);

pRoot->addChild(pShape);
  

// VRML nodes
SoVRMLTransform root = new SoVRMLTransform();
SoVRMLShape shape = new SoVRMLShape();
SoVRMLAppearance app = new SoVRMLAppearance();
SoVRMLMaterial mat = new SoVRMLMaterial();

mat.diffuseColor.SetValue(1, 0, 0);
app.material.SetValue(mat);
shape.appearance.SetValue(app);
shape.geometry.SetValue(new SoVRMLCone());

root.AddChild(shape);

// VRML nodes
SoVRMLTransform root = new SoVRMLTransform();
SoVRMLShape shape = new SoVRMLShape();
SoVRMLAppearance app = new SoVRMLAppearance();
SoVRMLMaterial mat = new SoVRMLMaterial();

mat.diffuseColor.setValue(1, 0, 0);
app.material.setValue(mat);
shape.appearance.setValue(app);
shape.geometry.setValue(new SoVRMLCone());

root.addChild(shape);

Here is a simple Open Inventor scene graph showing two cones, translated to slightly different positions, and both inheriting the color “red”:

  Separator
    {
    Material { diffuseColor 1 0 0 }
    # Red

      Separator
      {
      Transform { translation -1 0 0 }
      # Translate left Cone
        {
        }
      }

    Separator
      {
      Transform
        {
        translation 1 0 0
        }
      # Translate right Cone
        {
        }
      }
    }
        

  Separator
    {
    Separator
      {
      DEF Red Material { diffuseColor 1 0 0 }
      # Red
        Transform { translation -1 0 0 }
      # Translate left Cone
        {
        }
      }
    Separator
      {
      USE Red Transform { translation 1 0 0 }
      # Translate right Cone
        {
        }
      }
    }

Now each of the second level Separators is more representative of an object bundled with its appearance and position. In order to minimize the memory used by the scene graph and allow the two objects to share a common appearance, we name the Material node in the first object and reference it in the second object. Here is the equivalent VRML scene graph:

  Transform
    {
    children [
      Transform
      {
      translation -1 0 0 # Translate left
        children Shape
        {
        appearance DEF Red Appearance
          {
          material Material
            {
            diffuseColor 1 0 0
            }
          # Red
          }
        geometry Cone
          {
          }
        }
      }
    Transform
      {
      translation 1 0 0 # Translate right
        children Shape
        {
        appearance USE Red geometry Cone
          {
          }
        }
      }
    ]
    }