Ambient occlusion vertex color

Vertex Color AO

CryEngine2 uses vertex color for baked ambient occlusion. Vertex color is fairly inexpensive because it doesn't require memory-hungry textures.

Vertex color AO works well for meshes that use tiled textures, like environment models, because the tiling prevents unique lighting from being added to the textures. In this case textured AO would require a separate non-tiled texture using a second set of UVs, which would increase the vertex count for the model and increase the texture memory.

The downside of vertex color is that AO resolution will be dependent on the complexity of the mesh. The less vertices there are, the less precise the shading will be.

For AO vertex color baking methods, see the thread Baking Vertex Illumination without using radiosity on the Polycount forum.

Baking Vertex Color AO in 3DSMax

1. Place skylight anywhere

1. Set Sky color to white
2. Turn on "Cast Shadows" (Optional)

1. Render>Render

1. Advance lighting tab
2. Select Advanced Lighting Rollout
3. Set advance lighting to radiosity
   1. Radiosity Processing Parameters Rollout
   2. Initial quality \-> 95
   3. Refine Iterations (All Objects) \-> 1
   4. Indirect Light Filter \-> 1
4. Rendering Parameters
   1. Re-Use Direct Illumination from Radiosity Solution
5. Under Radiosity Processing Parameters click start.

1. Select all the geometry

1. Command Panel -> Utility Tab -> More...
   1. Assign Vertex Colors
   2. Vertex Illum
   3. Lighting Only
   4. Color by Vertex
   5. Radiosity, Reuse Direct Illum. From Solution
   6. Assign to selected