Vertex color properties, also known as color at vertices properties or CAVs, are colors stored in the polynodes (subvertices) of an object. They can be used for a variety of purposes, such as storing surface color, illumination, or custom data. If necessary, you can store several vertex color properties on the same object.
Every polygon has a polynode for each of its corners, so at a given vertex there are as many polynodes as there are polygons that share that vertex. The color information is interpolated between polynodes — for example, if you paint each corner of a square polygon a different color, then the center of the polygon would display a blend of each of the four colors.
The polygonal model to the left has a base color applied to it using a Lambert surface shader. Applying a surface shader is a good way to give your model or object a background color before painting its vertices with the Color at Vertices tool.
Alternatively, you can paint every other polygon so as to avoid using a material shader.
The polygonal model to the right was given a face full of stubble using the Color at Vertices tool. A brownish color was defined and then painted directly on the model’s polygons using a little transparency to blend the skin color (applied using the Lambert shader).
In this example, a combination of polygon and vertex bleeding was used.
Vertex colors are often used by game developers because they are an efficient method of coloring models. Because it is applying a constant color and allows you to simulate lighting (by painting luminance), game developers are able to remove lights from their scenes, thereby gaining a great deal of memory and performance, especially when rendering. Of course, the quality of results you can obtain by painting colors on vertices is entirely dependent on the density of the polygon mesh.
Vertex color properties support 8-bit RGBA values, as well as HDR RGBA values.
