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POCGFX shader extracting data from alpha channel
 

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  1. POCGFX shader extracting data from alpha channel
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    <p>I posted this as well on Nvidia Developer discussion.</p> <p><a href="http://forums.developer.nvidia.com/devforum/discussion/9946/extracting-numbers-cgfx-shader" rel="nofollow">http://forums.developer.nvidia.com/devforum/discussion/9946/extracting-numbers-cgfx-shader</a></p> <p>I am learning to write my first cgfx shader- a terrain shader. So I can only use 1 vertex channel (the alpha channel) and I want it to store 3 masks. I programmed a script no problem in the 3d App Maya where I can store 1 mask in the tenths place, 1 in the hundreths, and 1 in the thousandths place. </p> <p>Each original painted mask is clamped at 0 - .9 (to prevent zeroing out with fmod) so if a vert has:</p> <p>mask 1 =.857</p> <p>mask 2 =.345</p> <p>mask 3 -.948</p> <p>the combined alpha channel for this vert is = .839</p> <p>The problem I am having is I cannot get these masks extracted into seperate masks properly in my shader. </p> <p>If I output the Mask1 I get the correct nicely blended mask. I do this by:</p> <pre><code>float Mask1 = (fmod((Mcolor * 10f ), 10f)) *.111f; </code></pre> <p>If I output the Mask2 I get all these weird artifacts. It looks like the mask1 is pushing itself ontop, even when I am only outputting Mask2. I am positive the math works, I have run the same thing in Maya to store the values to begin with. Can anyone tell me why this is happening? </p> <p>Even:</p> <pre><code>float Mask2 = frac(Mcolor *10); </code></pre> <p>which should just push the mask 2 over into tenths place and erase Mask 1 results in the same artifacts. </p> <pre><code>float Mcolor = In.VertColor.a; float Mask1 = (fmod((Mcolor * 10f ), 10f)) *.111f; float Mask2 = (fmod((Mcolor * 100f ), 10f)) *.111f; </code></pre> <p>I posted some images of the issue on the Nvidia forum, but I can't post here becuase of spam prevention. </p> <p><a href="http://forums.developer.nvidia.com/devforum/discussion/9946/extracting-numbers-cgfx-shader" rel="nofollow">http://forums.developer.nvidia.com/devforum/discussion/9946/extracting-numbers-cgfx-shader</a></p> <p>Help is much appreciated -thanks for reading through! Please explain your response if you can/ have time, I am new to programming so the more descriptive the better!</p>
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    1. COOkay I found the issue. I need to do this in the vertex shader, not the pixel shader. So now my question is. How can I output something from the vertex shader to the pixel shader multiple times. Eg I need to output the vertex color as a float 4 to the pixel shader 4 times after performing some different math operations on the vertex color in the vert shader? can I do this? I tried creating an empty float4 color2, reading the In.vertcolor from In.color and outputing that... I dont get any errors but my texture is white. Its just reading any empty float 4...
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