//Cg


#define NEAR 0.5
#define FAR 400


float unpackDepth(uniform float wnear, uniform float wfar, float s){
    // depth equations from http://www.codermind.com/articles/Depth-buffer-tutorial.html
    // Hopefully they are correct
    //(wfar - (wnear * wfar)/w) / (wfar - wnear) = s
    // w = (wnear * wfar)/(wfar - s*(wfar - wnear))
    return (wnear * wfar)/(wfar - s*(wfar - wnear));
}


void vshader(float4 vtx_position : POSITION,
             out float4 l_position : POSITION,
             out float2 l_texcoord : TEXCOORD0,
             out float2 l_texcoordD : TEXCOORD1,
             uniform float4 texpad_depth,
             uniform float4x4 mat_modelproj)
{
   l_position = mul(mat_modelproj, vtx_position);
   l_texcoord = vtx_position.xz;
   l_texcoordD = (vtx_position.xz * texpad_depth.xy) + texpad_depth.xy;
}


void fshader(out float4 o_color: COLOR,
             float2 l_texcoord : TEXCOORD0,
             float2 l_texcoordD : TEXCOORD1,
             uniform float2 k_camera_fov_sin,
             uniform sampler2D k_depth : TEXUNIT0)
{
   float pixel_depth = tex2D(k_depth, l_texcoordD).r;

   float z_pos = unpackDepth(NEAR, FAR, pixel_depth);
   float x_pos = k_camera_fov_sin.x * l_texcoordD.x * pixel_depth;
   float y_pos = k_camera_fov_sin.y * l_texcoordD.y * pixel_depth;

   float3 pixel_pos = float3(x_pos, y_pos, z_pos);

   o_color.rgb = pixel_pos;
   o_color.a = 1;
}