panda3d/samples/shadows/caster.sha

//Cg

void vshader(float4 vtx_position : POSITION,
             uniform float4x4 mat_modelproj,
             uniform float4 k_scale,
             out float4 l_position : POSITION,
             out float4 l_pos : TEXCOORD0
             )
{
  float4 position = vtx_position * k_scale;
  l_pos = mul(mat_modelproj, position);
  l_position = l_pos;
}

void fshader(in float4 l_pos : TEXCOORD0,
             out float4 o_color : COLOR)
{
  float z = (l_pos.z / l_pos.w) * 0.5 + 0.5;
  o_color = float4(z, z, z, 1);
}