source: GTP/trunk/App/Demos/Vis/FriendlyCulling/src/shaders/FragmentSsao.cg @ 2810

struct INPUTDATA
{
        float2 diffuseTexCoords : TEXCOORD0;
        
};

struct OUTPUTDATA
{
        float4 color                    : COLOR0;

};

#define SAMPLES                         24

//kustls magic sample positions
static const float2 samples[SAMPLES] =
        {
                {-0.326212f, -0.405805f},
                {-0.840144f, -0.07358f},
                {-0.695914f, 0.457137f},
                {-0.203345f, 0.620716},
                {0.96234f, -0.194983f},
                {0.473434f, -0.480026f},
                {0.519456, 0.767022f},
                {0.185461f, -0.893124f},
                {0.507431f, 0.064425f},
                {0.89642f, 0.412458f},
                {-0.32194f, -0.932615f},
                {-0.791559f, -0.597705f},
                {0.326212f, 0.405805f},
                {0.840144f, 0.07358f},
                {0.695914f, -0.457137f},
                {0.203345f, -0.620716},
                {-0.96234f, 0.194983f},
                {-0.473434f, 0.480026f},
                {-0.519456, -0.767022f},
                {-0.185461f, 0.893124f},
                {-0.507431f, -0.064425f},
                {-0.89642f, -0.412458f},
                {0.32194f, 0.932615f},
                {0.791559f, 0.597705f}
        };
        
//based on kustls shader        
OUTPUTDATA main(INPUTDATA input,
                                uniform sampler2D positions,
                                uniform sampler2D colors,
                                uniform sampler2D normals,
                                const uniform float4x4 projectionTransformation,
                                uniform sampler2D noiseTexture                          
                                )
{
                        
        OUTPUTDATA o;

        float4 centerPositionW = tex2D(positions, input.diffuseTexCoords);
        float3 centerPosition = centerPositionW.xyz;
        float3 centerNormal = tex2D(normals, input.diffuseTexCoords).xyz;
        float3 centerColor = tex2D(colors, input.diffuseTexCoords).xyz;

        // Check in a circular area around the current position.
        // Shoot vectors to the positions there, and check the angle to these positions.
        // Summing up these angles gives an estimation of the occlusion at the current position.

        float total_ao = 0.0;
        const float areaSize = 4.0f;
        const float sampleIntensity = 0.1;

        for (int sample = 0; sample < SAMPLES; sample++)
        {
                float2 offset = samples[sample];
                
                //sample noisetex; r stores costheta, g stores sintheta
                float3 randomRotation = tex2D(noiseTexture, input.diffuseTexCoords*10.0f).xyz;
                                
                float2 offsetTransformed;
                offsetTransformed.x = randomRotation.r*offset.x - randomRotation.g*offset.y;
                offsetTransformed.y = randomRotation.g*offset.x + randomRotation.r*offset.y;
                
                
                float2 texcoord = input.diffuseTexCoords + offsetTransformed * areaSize*(1.0f-centerPositionW.w);
                
                float3 sample_position = tex2D(positions, texcoord).xyz;
                
                float3 vector_to_sample = sample_position - centerPosition;
                float length_to_sample = length(vector_to_sample);
                float3 direction_to_sample = vector_to_sample / length_to_sample;
                
                // Angle between current normal and direction to sample controls AO intensity.
                float angle = dot(direction_to_sample, centerNormal);
                angle = max(angle, 0.0);
                
                // Distance between current position and sample position controls AO intensity.
                float distance_intensity = 2.0 - 2.0f*length_to_sample;
                distance_intensity = max(distance_intensity, 0.0);
                
                total_ao += angle * sampleIntensity * distance_intensity;
        }
        
        
        o.color.rgb = (1.0f-total_ao)*saturate(centerColor);
        

        return o;
}