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Texture Blending

Started by Christoph Jul 5, 2004 at 12:36 PM 2 replies 850+ views

Original Post

Jul 5, 2004 at 12:36 PM

Hi, I have two cloud textures (n texture stage 0 and 1) which I'm blending between to simulate cloud movement in the sky. These are my settings:



d3dDev.RenderState.DestinationBlend = Blend.InvSourceColor
d3dDev.RenderState.SourceBlend = Blend.SourceColor
d3dDev.RenderState.AlphaBlendEnable = True
d3dDev.RenderState.TextureFactor = Color.FromArgb(a, 0, 0, 0).ToArgb

d3dDev.TextureState(0).ColorOperation = TextureOperation.BlendFactorAlpha
d3dDev.TextureState(0).ColorArgument1 = TextureArgument.TextureColor
d3dDev.TextureState(0).ColorArgument2 = TextureArgument.Current

d3dDev.TextureState(1).ColorOperation = TextureOperation.BlendFactorAlpha
d3dDev.TextureState(1).ColorArgument1 = TextureArgument.Current
d3dDev.TextureState(1).ColorArgument2 = TextureArgument.TextureColor

The variable a changes slowly from 0 to 255 and back. This sort of works. But I noticed a mistake: There are many transparent (black) areas through which you are able to see the sky color. But the blending doesn't work properly here: When the factor a changes, black mingled with black doesn't stay black, but becomes a dark grey before changing to black again. So the sky color between the clouds gets darker and brighter from time to time. Can somebody please tell me how I perfectly blend two cloud textures, whereas black means transparent? Thanks, Chris

Namethatnobodyelsetook

118

Namethatnobodyelsetook

Jul 5, 2004 at 1:33 PM

Shouldn't stage 0 just be selectarg1, texturecolor? Stage 1 will then blend between it's texture and the texture from stage 0, based on TFACTOR alpha.

Right now you're blending the first cloud texture with the vertex color THEN blending that with the new texture. Thus, when blend = 50%, you're getting this:

cloud1 at 25%, vertex color at 25%, and cloud2 at 50%.

Christoph

Author

Christoph

Jul 5, 2004 at 2:15 PM

Oh yeah, right. I thought that I'd have to use alpha on the first texture as well, so that it gets fainter while the other becomes more opaque. However, now it works. Thank you.

SoaringTortoise

Jul 5, 2004 at 3:43 PM

You might also want to try using dds files - alpha-mapped textures can make the blending even better because you can have semi-transparent parts of the texture. I did something like this with my water and looks pretty decent.

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