Hi all

I'm trying to blend 4 textures into one and then save the resulting texture in a new bitmap.

Some more detail:

I have 4 textures, Layer0 - Layer3 and 3 alphamaps, Alpha1 - Alpha3

The blending basically works like this:

Color = ((Layer0 * (1 - Alpha1) + Layer1 * Alpha1) * (1 - Alpha2) + Layer2 * Alpha2) * (1 - Alpha3) + Layer3 * Alpha3

Or (in sequence):

Color = Layer0
Color = Color * (1 - Alpha1) + Layer1 * Alpha1
Color = Color * (1 - Alpha2) + Layer2 * Alpha2
Color = Color * (1 - Alpha3) + Layer3 * Alpha3

All textures have the same size (2048x2048) and are bitmaps that I have in memory.

I currently combine them by doing an iteration over all pixels and calculating the values. This takes 10 seconds (which is NOT acceptable).

Can I do this using DirectX and then save the result? I need the result as a bitmap that I can save again, so having it only on the graphic card is not sufficient.

Cheers

Remo

Use a 2048x2048 2D render target, then draw the 3 layers using the shader hardware. You might need to write a pixel shader to use the alpha maps.

You can actually copy the implementation of the splattingh you have in code into a pixelshader, except that you use "tex2D(textureSampler1, texCoord)" to get the actual color values.