Stefan Röttger

← Scene Graph Flattening | ● | Scene Graph APIs →

Previously the scene graph was implicitly defined. Given an explicit data structure, containing a scene graph, it can be translated into direct rendering commands by the following simple method:

• Apply the camera transformation first
• Walk the graph depth-first (by always keeping one hand on the “railing”).
• Whenever a transformation node is traversed down-wards, remember the actual modeling transformation (by issuing a glPushMatrix command). Then apply the respective local transformation.
• Whenever a geometry node is traversed down-wards, render it with the actual modeling transformation.
• Whenever a transformation node is traversed up-wards, restore the previous modeling transformation (by issuing a glPopMatrix command).

For example the following scene graph

is translated into the following direct OpenGL command sequence

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