// Pass 3 (remap alpha): vertex program.
void main (float4 pObj        : POSITION,
           out float4 pClip   : POSITION,
           out float zLinear  : TEXCOORD0,
           uniform float4x4 mvp,
           uniform float4x4 mv)
{
    pClip = mul(mvp, pObj);      // obj -> clip space
    zLinear = mul(mv, pObj).z;   // z in eye space
}
