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qorthos

SlimDX and SSAO

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qorthos    168

Hi everyone.  I'm coming up against a wall against and need help!  I've been trying to figure out how to implement SSAO for over a week now and keep getting garbage.  A lot of the code I'm using is lifted from other places (MJP, Jose Mendez).  I think I understand it.  Mostly...

 

I'm rendering my scene to a diffuse color view, normal view (output.Normal = input.Normal * 0.5f + 0.5f) and a depth buffer (output.Depth = input.Depth.x / input.Depth.y)

 

This is the scene I'm rendering (just showing diffuse colors):

2cRVzoj.jpg

 

The cubes are 1 unit cubed.

 

This is my SSAO shader:

Texture2D DepthTexture	: register(t0);
Texture2D NormalTexture : register(t1);
Texture2D RandomTexture : register(t2);

cbuffer Once : register(cb0)
{
	float Bias;
	float Intensity;
	float Radius;
	float Scale;
}

cbuffer OncePerFrame : register(cb1)
{
	float4x4	Projection;
	float4x4	InvProjection;
	float		FarClip;
}

SamplerState sampleType
{
    Filter = MIN_MAG_MIP_LINEAR;
    AddressU = CLAMP;
    AddressV = CLAMP;
};

struct VS_IN
{
	float4 Position  : POSITION;
	float2 Texcoords : TEXCOORD0;
};

struct VS_OUT
{
	float4 Position	 : SV_POSITION;
	float2 Texcoords : TEXCOORD0;
};


VS_OUT VS( VS_IN input)
{
	VS_OUT output = (VS_OUT)0;
	
	output.Position = input.Position;
	output.Texcoords = input.Texcoords;

	return output;
}


float3 GetPosition(float2 vTexCoord)
{
    // Get the depth value for this pixel
    float z = DepthTexture.Sample(sampleType, vTexCoord).r;

    // Get x/w and y/w from the viewport position
    float x = vTexCoord.x * 2 - 1;
    float y = (1 - vTexCoord.y) * 2 - 1;
    float4 vProjectedPos = float4(x, y, z, 1.0f);

    // Transform by the inverse projection matrix
    float4 vPositionVS = mul(vProjectedPos, InvProjection);  

    // Divide by w to get the view-space position
    return vPositionVS.xyz / vPositionVS.w;  
}

float DoAmbientOcclusion(in float2 tcoord, in float2 uv, in float3 p, in float3 cnorm)
{
	float3 diff = GetPosition(tcoord + uv) - p;
	const float3 v = normalize(diff);
	const float d = length(diff) * Scale;
	return max(0.0, dot(cnorm, v) - Bias) * (1.0 / (1.0 + d)) * Intensity;
}


float4 PS(VS_OUT input) : SV_Target
{
	const float2 vec[4] = 
	{
		float2(1, 0),float2(-1, 0),
		float2(0, 1),float2(0, -1)
	};
	
	float3 p = GetPosition(input.Texcoords);
	float3 n = NormalTexture.Sample(sampleType, input.Texcoords).xyz * 2 - 1;
	float2 rand = RandomTexture.Sample(sampleType, input.Texcoords).xy;
	
	float ao = 0.0f;
	float rad = Radius / p.z;
	
	//**SSAO Calculation**//

	int iterations = 4;
	for (int j = 0; j < iterations; ++j)
	{
		float2 coord1 = reflect(vec[j], rand) * rad;
		float2 coord2 = float2(coord1.x * 0.707 - coord1.y * 0.707,
								coord1.x * 0.707 + coord1.y * 0.707);
		
		ao += DoAmbientOcclusion(input.Texcoords, coord1 * 0.25, p, n);
		ao += DoAmbientOcclusion(input.Texcoords, coord2 * 0.50, p, n);
		ao += DoAmbientOcclusion(input.Texcoords, coord1 * 0.75, p, n);
		ao += DoAmbientOcclusion(input.Texcoords, coord2 * 1.00, p, n);
	}

	ao /= (float)iterations * 4.0;
	
	//**END**//

	return float4(1 - ao, 1-ao, 1-ao, 1);
}

 

 

I've gone through and debugged the shader, all of my settings are being set.  I'm reasonably sure that I'm getting position from depth correctly and decoding the normal right.  

 

Is the problem with the SSAO settings?  I'm using this:

 

            float bias = 0.01f;
            float intensity = 0.5f;
            float radius = 1.1f;
            float scale = 0.5f;
 
Which seems like are right...  Aggh.  I'm pulling my hair out here.

 

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