struct VOut {
    float4 p      : POSITION;
    float2 uv     : TEXCOORD0;
    float3 a      : TEXCOORD1;
    float4 ssaoUV : TEXCOORD2;
};

VOut ambient_vs(
    in float4 p : POSITION,
    in float2 uv : TEXCOORD0,
    uniform float3 ambient,
    uniform float4x4 wvp
    ) {
    VOut OUT;
    OUT.p = mul(wvp, p);
    // just use projective texture which == OUT.p
    OUT.ssaoUV = OUT.p;
    OUT.a = ambient;
    OUT.uv = uv;
    return OUT;
}

struct PIn {
    float2 uv     : TEXCOORD0;
    float3 a      : TEXCOORD1;
    float4 ssaoUV : TEXCOORD2;
};

float4 ambient_ps(PIn IN,
    uniform sampler2D diffuseTex : TEXUNIT0,
    uniform sampler2D ssaoTex    : TEXUNIT1): COLOR0 {
    float2 ssaoUV = IN.ssaoUV.xy / IN.ssaoUV.w; // perspective divide

    // move into texture space
    ssaoUV = (float2(ssaoUV.x, -ssaoUV.y) + 1.0) * 0.5;
    float3 ssao = tex2D(ssaoTex, ssaoUV).rgb;

    float3 diffuse = tex2D(diffuseTex, IN.uv).rgb;
    return float4(diffuse * IN.a/* * ssao*/, 1);
}