User's Manual

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0
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13.12. GFXRENDERSTATE_MAP_COLOR_BLEND_STAGES
The Rendering Engine supports three map color blend stages for the red, green, and blue channels. Any
of these stages may perform an operation utilizing up to two texels from the Mapping Engine, the iterated
face color, the iterated alpha and/or a constant color.
Figure 39. State Variable Relationships
Coordinate Sets Map Information
Blending Stages
Texels
The following equations are supported by each blending stage.
Blend Equation Description
Color
out
= Arg1 Select Arg1
Color
out
= Arg2 Select Arg2
Color
out
= Arg1 * Arg2 Modulate
Color
out
= Arg1 * Arg2 * 2 Modulate and Multiply by 2
Color
out
= Arg1 * Arg2 * 4 Modulate and Multiply by 4
Color
out
= Arg1 + Arg2 Add
Color
out
= Arg1 - Arg2 Subtract
Color
out
= Arg1 + Arg2 - 0.5 Add Signed (Excess 128)
Color
out
= α
Iterated
* Arg1 + (1 - α
Iterated
) * Arg2 Linearly Blend using Iterated Alpha
Color
out
= α
Factor
* Arg1 + (1 - α
Factor
) * Arg2 Linearly Blend using Alpha Factor
Color
out
= α
Texel0
* Arg1 + (1 - α
Texel0
) * Arg2 Linearly Blend using Texel0’s Alpha
Color
out
= α
Texel1
* Arg1 + (1 - α
Texel1
) * Arg2 Linearly Blend using Texel1’s Alpha
Color
out
= Color
Texel0
* Arg1 + (1 - Color
Texel0
) * Arg2 Linearly Blend using Texel0’s Color
Color
out
= Color
Texel1
* Arg1 + (1 - Color
Texel1
) * Arg2 Linearly Blend using Texel1’s Color
The settings for these stages are specified in the following instruction. When enable a stage for color
operation, the corresponding alpha stage will also be enabled. The arguments and operation fields of the
corresponding alpha stage must be programmed accordingly.