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DX11 trying with ssao

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Hi! I am trying to implement simple SSAO postprocess. The main source of my knowledge on this topic is that awesome tutorial.

But unfortunately something doesn't work... And after a few long hours I need some help. Here is my hlsl shader:

float3 randVec = _noise * 2.0f - 1.0f; // noise: vec: {[0;1], [0;1], 0} 
float3 tangent = normalize(randVec - normalVS * dot(randVec, normalVS)); 
float3 bitangent = cross(tangent, normalVS); 
float3x3 TBN = float3x3(tangent, bitangent, normalVS); 
float occlusion = 0.0; 
for (int i = 0; i < kernelSize; ++i) 
{ 
	float3 samplePos = samples[i].xyz; // samples: {[-1;1], [-1;1], [0;1]} 
	samplePos = mul(samplePos, TBN); 
	samplePos = positionVS.xyz + samplePos * ssaoRadius; 
				
	float4 offset = float4(samplePos, 1.0f); 
	offset = mul(offset, projectionMatrix); 
	offset.xy /= offset.w; 
	offset.y = -offset.y; 
	offset.xy = offset.xy * 0.5f + 0.5f; 
				
	float sampleDepth = tex_4.Sample(textureSampler, offset.xy).a; 
	sampleDepth = vsPosFromDepth(sampleDepth, offset.xy).z; 
				
	const float threshold = 0.025f; 
	float rangeCheck = abs(positionVS.z - sampleDepth) < ssaoRadius ? 1.0 : 0.0; 
	occlusion += (sampleDepth <= samplePos.z + threshold ? 1.0 : 0.0) * rangeCheck; 
} 
occlusion = saturate(1 - (occlusion / kernelSize));

And current result: http://imgur.com/UX2X1fc

I will really appreciate for any advice!

Edited by gsc

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I don't see this very important bit of math to transform/scale your normals:

vec3 normal = normalVS.xyz * 2.0 - 1.0;
normal = normalize(normal);

I pulled this from the tutorial you referenced (although, if you arent using Normal Maps, you might not need this)

Edited by missionctrl
changed code to match OPs code

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@missionctrl yes, I have that part of math, I am using a buffer with normals in view space (look at the attachment)

@KarimIO hmmm... if the shader hasn't any mistakes, then my data from buffers should be wrong...

Generally, I have normal buffer ( and depth buffer to reconstruct VS of geometry, but for test purpose I created special position buffers to eliminate possibility of mistakes in calculations from the depth buffer.

All buffers and results here: http://imgur.com/a/nm0bA

I have no idea, why version with positions read directly from the buffer is so noisy and the second one hasn't virtually any noise.

Edited by gsc

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