Creating Blending Stages

A blending stage is a set of texture operations and their arguments that define how textures are blended. When making a blending stage, C++ applications invoke the IDirect3DDevice9::SetTextureStageState method. The first call specifies the operation that is performed. Two additional invocations define the arguments to which the operation is applied. The following code example illustrates the creation of a blending stage.

// This example assumes that lpD3DDev is a valid pointer to an
// IDirect3DDevice9 interface.

// Set the operation for the first texture.
d3dDevice->SetTextureStageState(0, D3DTSS_COLOROP, D3DTOP_ADD);

// Set argument 1 to the texture color.
d3dDevice->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_TEXTURE);

// Set argument 2 to the iterated diffuse color.
d3dDevice->SetTextureStageState(0, D3DTSS_COLORARG2, D3DTA_DIFFUSE);

Texel data in textures contain color and alpha values. Applications can define separate operations for both color and alpha values in a single blending stage. Each operation, color, and alpha, has its own arguments. For details, see D3DTEXTURESTAGESTATETYPE.

Although not part of the Direct3D API, you can insert the following macros into your application to abbreviate the code required for creating texture blending stages.

#define SetTextureColorStage( dev, i, arg1, op, arg2 )     \
	dev->SetTextureStageState( i, D3DTSS_COLOROP, op);      \
	dev->SetTextureStageState( i, D3DTSS_COLORARG1, arg1 ); \
	dev->SetTextureStageState( i, D3DTSS_COLORARG2, arg2 );

#define SetTextureAlphaStage( dev, i, arg1, op, arg2 )     \
	dev->SetTextureStageState( i, D3DTSS_ALPHAOP, op);      \
	dev->SetTextureStageState( i, D3DTSS_ALPHAARG1, arg1 );  \
	dev->SetTextureStageState( i  D3DTSS_ALPHAARG2, arg2 );