Intel 815 manual Gfxrenderstatemapalphablendstages, Blend Equation Description

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Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

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13.13.GFXRENDERSTATE_MAP_ALPHA_BLEND_STAGES

The Rendering Engine supports three map color blend stages for the alpha channel. Any of these stages may perform an operation utilizing the alpha channel from up to two texels from the Mapping Engine, the iterated alpha and/or a constant color.

Figure 40. State Variable Relationships

Coordinate Sets

Map Information

Texels

Blending Stages

The following equations are supported by each blending stage.

Blend Equation

Description

 

 

Alphaout = Arg1

Select Arg1

 

 

Alphaout = Arg2

Select Arg2

 

 

Alphaout = Arg1 * Arg2

Modulate

 

 

Alphaout = Arg1 * Arg2 * 2

Modulate and Multiply by 2

 

 

Alphaout = Arg1 * Arg2 * 4

Modulate and Multiply by 4

 

 

Alphaout = Arg1 + Arg2

Add

 

 

Alphaout = Arg1 + Arg2 - 0.5

Add Signed (Excess 128)

 

 

Alphaout = αIterated * Arg1 + (1 - αIterated) * Arg2

Linearly Blend using Iterated Alpha

 

 

Alphaout = αFactor * Arg1 + (1 - αFactor) * Arg2

Linearly Blend using Alpha Factor

 

 

Alphaout = αTexel0 * Arg1 + (1 - αTexel0) * Arg2

Linearly Blend using Texel0’s Alpha

 

 

Alphaout = αTexel1 * Arg1 + (1 - αTexel1) * Arg2

Linearly Blend using Texel1’s Alpha

 

 

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Page 230
Image 230
Intel 815 manual Gfxrenderstatemapalphablendstages, Blend Equation Description