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alpha blending

Started by 16bit_port Sep 15, 2010 at 12:15 PM 2 replies 900+ views

Original Post

Sep 15, 2010 at 12:15 PM

Using : D3D9 and shader model 2.0

Is it possible to perform alpha blending in the pixel shader and not have the color output (from said pixel shader) sent to the blending stage? If so, how?

Also, is it possible to set clear all the alpha blending settings that were called through m_pd3dDevice->SetRenderState() back to default?

MJP

Mod

2,105

MJP

Sep 15, 2010 at 1:26 PM

A pixel shader can't read the contents of the render target. So the only way it can blend is if you sample a texture and blend with that, and then output.

You can't just set all render states back to default. If you want you can use state blocks, which "capture" state a certain point so that you can revert to that state.

unbird

329

unbird

Sep 15, 2010 at 2:17 PM

Quote:
...not have the color output (from said pixel shader) sent to the blending stage?

There are several ways to mask pixels, provided you set up appropriate render-states and calculations in your shader.

- alpha-test
- stencil-test
- depth-test

And in the pixel-shader you can use clip(x) to omit pixels.

DragonGeo2

Sep 15, 2010 at 7:28 PM

Quote:
Original post by 16bit_port
Using : D3D9 and shader model 2.0

Is it possible to perform alpha blending in the pixel shader and not have the color output (from said pixel shader) sent to the blending stage? If so, how?

Um, what are you trying to do that requires you not use the alpha blending stage? We might be able to help you come up with a method that does not require doing manual alpha blending in the pixel shader.

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