source: GTP/trunk/App/Demos/Illum/IBRBillboardCloudTrees/OGRE/IBRTreesOGRE/media/oldgeneral/depth_shadow_mapping_fp.shd @ 1493

float4 gambient;
sampler textureAlpha: register(s0);

float4 main(float3 normal: TEXCOORD0, float3 lightVec: TEXCOORD1, float4 texCoord: TEXCOORD2) : COLOR
{
   float depth = length(lightVec.xyz);
   if (tex2D(textureAlpha,texCoord).w > 0.0) 
   {
        return float4(gambient.xyz,depth);
   }
   else
   {
        discard;
   }
}