#line 1 "z-ssao-in.txt"

#define SAMPLE_COUNT 8

struct v2f_ao {
	float4 pos : POSITION;
	float2 uv : TEXCOORD0;
	float2 uvr : TEXCOORD1;
};

sampler2D _CameraDepthNormalsTexture;
sampler2D _RandomTexture;
float4 _Params; // x=radius, y=minz, z=attenuation power, w=SSAO power
float4 _ProjectionParams;

inline float3 DecodeViewNormalStereo( float4 enc4 )
{
	float kScale = 1.7777;
	float3 nn = enc4.xyz*float3(2*kScale,2*kScale,0) + float3(-kScale,-kScale,1);
	float g = 2.0 / dot(nn.xyz,nn.xyz);
	float3 n;
	n.xy = g*nn.xy;
	n.z = g-1;
	return n;
}
inline float DecodeFloatRG( float2 enc )
{
	float2 kDecodeDot = float2(1.0, 1/255.0);
	return dot( enc, kDecodeDot );
}
inline void DecodeDepthNormal( float4 enc, out float depth, out float3 normal )
{
	depth = DecodeFloatRG (enc.zw);
	normal = DecodeViewNormalStereo (enc);
}

half frag_ao (v2f_ao i, int sampleCount, float3 samples[SAMPLE_COUNT])
{
	// read random normal from noise texture
    half3 randN = tex2D (_RandomTexture, i.uvr).xyz * 2.0 - 1.0;    
    
    // read scene depth/normal
    float4 depthnormal = tex2D (_CameraDepthNormalsTexture, i.uv);
    float3 viewNorm;
    float depth;
    DecodeDepthNormal (depthnormal, depth, viewNorm);
    depth *= _ProjectionParams.z;
    float scale = _Params.x / depth;
    
    // accumulated occlusion factor
    float occ = 0.0;
    for (int s = 0; s < sampleCount; ++s)
    {
    	// Reflect sample direction around a random vector
        half3 randomDir = reflect(samples[s], randN);
        
        // Make it point to the upper hemisphere
        half flip = (dot(viewNorm,randomDir)<0) ? 1.0 : -1.0;
        randomDir *= -flip;
        // Add a bit of normal to reduce self shadowing
        randomDir += viewNorm * 0.3;
        
        float2 offset = randomDir.xy * scale;
        float sD = depth - (randomDir.z * _Params.x);

		// Sample depth at offset location
        float4 sampleND = tex2D (_CameraDepthNormalsTexture, i.uv + offset);
        float sampleD;
        float3 sampleN;
        DecodeDepthNormal (sampleND, sampleD, sampleN);
        sampleD *= _ProjectionParams.z;
        float zd = saturate(sD-sampleD);
        if (zd > _Params.y) {
        	// This sample occludes, contribute to occlusion
	        occ += pow(1-zd,_Params.z); // sc2
	        //occ += 1.0-saturate(pow(1.0 - zd, 11.0) + zd); // nullsq
        	//occ += 1.0/(1.0+zd*zd*10); // iq
        }        
    }
    occ /= sampleCount;
    return 1-occ;
}

half4 main (v2f_ao i) : COLOR
{
	const float3 RAND_SAMPLES[SAMPLE_COUNT] = {
		float3(0.01305719,0.5872321,-0.119337),
		float3(0.3230782,0.02207272,-0.4188725),
		float3(-0.310725,-0.191367,0.05613686),
		float3(-0.4796457,0.09398766,-0.5802653),
		float3(0.1399992,-0.3357702,0.5596789),
		float3(-0.2484578,0.2555322,0.3489439),
		float3(0.1871898,-0.702764,-0.2317479),
		float3(0.8849149,0.2842076,0.368524),
	};
    return frag_ao (i, SAMPLE_COUNT, RAND_SAMPLES);
}