3d render to alpha channel

Hi,

The idea is to make a shader that does this : http://www.youtube.com/watch?v=6r7hVWmNEcw&feature=g-upl

A friend of mine did this shader with HLSL

uniform extern texture ScreenTexture;    
    
    sampler ScreenS = sampler_state
    {
        Texture = <ScreenTexture>;    
    };
    
    float4 PixelShaderFunction(float2 texCoord: TEXCOORD0) : COLOR
    {
    	float4 color = tex2D(ScreenS, texCoord);
    
    	if(color.r < 1.0f)
    	{
    		return float4(0.0f, 0.0f, 0.0f, 0.0f);
    	}
    	else
    	{
    		return color;
    	}
    }
    
    technique GreenToAlpha
    {
        pass Pass1
        {
            PixelShader = compile ps_2_0 PixelShaderFunction();
        }
    }

Do you know the process that I can use with the free version of unity3D ?

Or maybe this shader have been already done in unity, if you have a link to it feel free to post it.

Sorry for my poor english.

Hi,

I’m the guy who wrote the HLSL code up here.
This shader is actually just a pixel shader taking all non-white pixels and turning them into a transparent one.
I made it to reproduce the effect shown on the video with DirectX.

What he needs here is how to render the 3d text on white background into a texture, send it to this shader (who needs to be converted to GLSL/CG) and draw it on his scene.

Hope this post clarify his demand.