Triangle Interpolants

During rendering, the pipeline interpolates vertex data across each triangle. Five possible types of data can be interpolated:

• Diffuse color
• Specular color
• Diffuse alpha (triangle opacity)
• Specular alpha
• Fog factor (taken from specular alpha for fixed function vertex pipeline and from fog register for programmable vertex pipeline)

The interpolation of the vertex data is dependent on the current shading mode, as shown in the following table.

The color and specular interpolants are treated differently, depending on the color model. In the RGB color model, the system uses the red, green, and blue color components in the interpolation.

The alpha component of a color is treated as a separate interpolant because device drivers can implement transparency in two different ways: by using texture blending or by using stippling.