Baking Surface Attributes with RenderMap
RenderMap allows you to capture a wide variety of surface information from scene objects, and bake that information into image files that can be reapplied to the rendermapped object and/or used for myriad other purposes.
RenderMap captures surface information by casting rays from a virtual camera in order to sample each point on an object’s surface.
The virtual camera can be perpendicular to the object’s surface or it can simulate the scene camera. In either case, you can position the camera directly on the object surface to rendermap only the object itself, or at a specified distance to bake objects between the virtual camera and the object into the rendermap.
The results are rendered as one or more 2D images that you can apply to the object as you would any other 2D texture.
Properties that are view-dependent, including specular highlights, reflections, refractions, and so on, are probably not a good idea to rendermap because they get “baked in” and don’t change from different viewpoints. The exception is when they're intended to be seen from a certain viewpoint only.
To generate rendermap images, you must specify a texture projection that the RenderMap property can use to determine the relationship between the points on the object’s surface and the target images. Some maps require additional information to generate properly.
RenderMap properties can be applied to polygon meshes, polygon clusters, NURBS surfaces, entire assembled surfaces, hierarchies, and groups. You can apply multiple RenderMap properties to a single object.
RenderMap takes advantage of satellite rendering, if it’s available. The default tile size is 32. You can change this value using the TileSize parameter of the RegenerateMaps() command. Changing the tile size can affect the rendering speed, depending on the complexity of the objects and the size of the maps. For more info about RegenerateMaps(), see the SDK Guide.
You can use RenderMap for a multitude of texturing tasks, including:
• Creating a single texture from two or more blended textures.
• Creating a 2D texture from a 3D procedural texture.
• Blending a texture with a light effect or with shadows that are cast on an object’s surface.
• Creating an illumination map.
• Creating maps of surface information, like normal maps, U and V basis maps, texel coverage maps, and surface position maps.
• Creating sprites.
The following example shows how you can use RenderMap to create a single texture (which includes lighting information) out of a complex render tree.
Before RenderMap
The disembodied hand shown below was textured using a combination of several images mixed together in a complex render tree, and lit using two infinite lights. The result is a highly detailed surface that incorporates color, bump, displacement, and lighting information, and takes a fair amount of time to render.
After RenderMap
To bake the hand’s surface attributes into a single texture file, a RenderMap property was applied to the hand, and a Surface Color map was generated. The resulting texture image was then applied directly to the Surface input of the hand’s material node. Finally, the scene lights were deleted, producing the result shown at right—a good approximation of the hand’s original appearance.
Because the hand’s illumination is baked into the rendermap image, you can get this result without using lights or an illumination shader.
Autodesk Softimage v.7.5