Panda3D - Design

Design

Panda3D is a scene graph engine. This means that the virtual world is initially an empty Cartesian space into which the game programmer inserts 3D models. Panda3D does not distinguish between "large" 3D models, such as the model of an entire dungeon or island, and "small" 3D models, such as a model of a table or a sword. Both large and small models are created using a standard modeling program such as Blender, 3ds Max, or Maya. The models are then loaded into Panda3D and inserted into the Cartesian space.

The Panda3D scene graph exposes the functionality of OpenGL and DirectX in a fairly literal form. For instance, OpenGL and DirectX both have fog capabilities. To enable fog in Panda3D, one simply stores the fog parameters on a node in the scene graph. The fog parameters exactly match the parameters of the equivalent calls in the underlying APIs. In this way, Panda3D can be seen as a thin wrapper around the lower-level APIs. Where it differs from them is that it stores the scene, whereas OpenGL and DirectX do not. Of course, it also provides higher-level operators, such as loading models, executing animations, detecting collisions, and the like.

Panda3D was first engineered before the existence of vertex and pixel shaders. It acquired support for manually written shaders in 2005. However, users have been slow to leverage modern per-pixel lighting techniques in their games. The developers theorize that this is because shader programming can be quite difficult, and that many game developers want the engine to handle it automatically.

To remedy this situation, the Panda3D developers have recently given Panda3D the ability to synthesize shaders automatically. This synthesis occurs if the 3D modeler marks a model for per-pixel lighting, or if the modeler applies a normal map, gloss map, self-illumination map, or other capability that exceeds the capabilities of the fixed-function pipeline. The intent of the synthesis is to render the model as the modeler intended, without any intervention from the programmer.