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By Mercesa
Hey folks. So I'm having this problem in which if my camera is close to a surface, the SSAO pass suddenly spikes up to around taking 16 milliseconds.
When still looking towards the same surface, but less close. The framerate resolves itself and becomes regular again.
This happens with ANY surface of my model, I am a bit clueless in regards to what could cause this. Any ideas?
In attached image: y axis is time in ms, x axis is current frame. The dips in SSAO milliseconds are when I moved away from the surface, the peaks happen when I am very close to the surface.
Edit: So I've done some more indepth profiling with Nvidia nsight. So these are the facts from my results
Count of command buffers goes from 4 (far away from surface) to ~20(close to surface).
The command buffer duration in % goes from around ~30% to ~99%
Sometimes the CPU duration takes up to 0.03 to 0.016 milliseconds per frame while comparatively usually it takes around 0.002 milliseconds.
I am using a vertex shader which generates my fullscreen quad and afterwards I do my SSAO calculations in my pixel shader, could this be a GPU driver bug? I'm a bit lost myself. It seems there could be a CPU/GPU resource stall. But why would the amount of command buffers be variable depending on distance from a surface?
Edit n2: Any resolution above 720p starts to have this issue, and I am fairly certain my SSAO is not that performance heavy it would crap itself at a bit higher resolutions.

By turanszkij
In DirectX 11 we have a 24 bit integer depth + 8bit stencil format for depthstencil resources ( DXGI_FORMAT_D24_UNORM_S8_UINT ). However, in an AMD GPU documentation for consoles I have seen they mentioned, that internally this format is implemented as a 64 bit resource with 32 bits for depth (but just truncated for 24 bits) and 32 bits for stencil (truncated to 8 bits). AMD recommends using a 32 bit floating point depth buffer instead with 8 bit stencil which is this format: DXGI_FORMAT_D32_FLOAT_S8X24_UINT.
Does anyone know why this is? What is the usual way of doing this, just follow the recommendation and use a 64 bit depthstencil? Are there performance considerations or is it just recommended to not waste memory? What about Nvidia and Intel, is using a 24 bit depthbuffer relevant on their hardware?
Cheers!

By gsc
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!

By isu diss
I'm trying to code Rayleigh part of Nishita's model (Display Method of the Sky Color Taking into Account Multiple Scattering). I get black screen no colors. Can anyone find the issue for me?
#define InnerRadius 6320000 #define OutterRadius 6420000 #define PI 3.141592653 #define Isteps 20 #define Ksteps 10 static float3 RayleighCoeffs = float3(6.55e6, 1.73e5, 2.30e5); RWTexture2D<float4> SkyColors : register (u0); cbuffer CSCONSTANTBUF : register( b0 ) { float fHeight; float3 vSunDir; } float Density(float Height) { return exp(Height/8340); } float RaySphereIntersection(float3 RayOrigin, float3 RayDirection, float3 SphereOrigin, float Radius) { float t1, t0; float3 L = SphereOrigin  RayOrigin; float tCA = dot(L, RayDirection); if (tCA < 0) return 1; float lenL = length(L); float D2 = (lenL*lenL)  (tCA*tCA); float Radius2 = (Radius*Radius); if (D2<=Radius2) { float tHC = sqrt(Radius2  D2); t0 = tCAtHC; t1 = tCA+tHC; } else return 1; return t1; } float RayleighPhaseFunction(float cosTheta) { return ((3/(16*PI))*(1+cosTheta*cosTheta)); } float OpticalDepth(float3 StartPosition, float3 EndPosition) { float3 Direction = normalize(EndPosition  StartPosition); float RayLength = RaySphereIntersection(StartPosition, Direction, float3(0, 0, 0), OutterRadius); float SampleLength = RayLength / Isteps; float3 tmpPos = StartPosition + 0.5 * SampleLength * Direction; float tmp; for (int i=0; i<Isteps; i++) { tmp += Density(length(tmpPos)InnerRadius); tmpPos += SampleLength * Direction; } return tmp*SampleLength; } static float fExposure = 2; float3 HDR( float3 LDR) { return 1.0f  exp( fExposure * LDR ); } [numthreads(32, 32, 1)] //disptach 8, 8, 1 it's 256 by 256 image void ComputeSky(uint3 DTID : SV_DispatchThreadID) { float X = ((2 * DTID.x) / 255)  1; float Y = 1  ((2 * DTID.y) / 255); float r = sqrt(((X*X)+(Y*Y))); float Theta = r * (PI); float Phi = atan2(Y, X); static float3 Eye = float3(0, 10, 0); float ViewOD = 0, SunOD = 0, tmpDensity = 0; float3 Attenuation = 0, tmp = 0, Irgb = 0; //if (r<=1) { float3 ViewDir = normalize(float3(sin(Theta)*cos(Phi), cos(Theta),sin(Theta)*sin(Phi) )); float ViewRayLength = RaySphereIntersection(Eye, ViewDir, float3(0, 0, 0), OutterRadius); float SampleLength = ViewRayLength / Ksteps; //vSunDir = normalize(vSunDir); float cosTheta = dot(normalize(vSunDir), ViewDir); float3 tmpPos = Eye + 0.5 * SampleLength * ViewDir; for(int k=0; k<Ksteps; k++) { float SunRayLength = RaySphereIntersection(tmpPos, vSunDir, float3(0, 0, 0), OutterRadius); float3 TopAtmosphere = tmpPos + SunRayLength*vSunDir; ViewOD = OpticalDepth(Eye, tmpPos); SunOD = OpticalDepth(tmpPos, TopAtmosphere); tmpDensity = Density(length(tmpPos)InnerRadius); Attenuation = exp(RayleighCoeffs*(ViewOD+SunOD)); tmp += tmpDensity*Attenuation; tmpPos += SampleLength * ViewDir; } Irgb = RayleighCoeffs*RayleighPhaseFunction(cosTheta)*tmp*SampleLength; SkyColors[DTID.xy] = float4(Irgb, 1); } }

By amadeus12
I made my obj parser
and It also calculate tagent space for normalmap.
it seems calculation is wrong..
any good suggestion for this?
I can't upload my pics so I link my question.
https://gamedev.stackexchange.com/questions/147199/howtodebugcalculatingtangentspace
and I uploaded my code here
ObjLoader.cpp
ObjLoader.h



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