but all pixels have to be same.
Problem started when I tried to implement volumetric clouds (you can see noise here video). Then I just simplified code. Also original code and shader which draw volumetric clouds work fine on OpenGL.
CMake project is available here
There are steps:
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Init vulkan.
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Create pipeline, image and etc.
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Call vkCmdDispatch()
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Call vkMapMemory() to get result
VkCommandBuffer pCommandBuffer; //draw { pCommandBuffer = beginCommandBuffer(commandPool); vkCmdBindPipeline(pCommandBuffer, VK_PIPELINE_BIND_POINT_COMPUTE, pipeline); vkCmdBindDescriptorSets( pCommandBuffer, VK_PIPELINE_BIND_POINT_COMPUTE, pipelineLayout, 0, 1, &descriptorSet, 0, nullptr); vkCmdDispatch(pCommandBuffer, alignUp(WIDTH, (uint32)8) / 8, alignUp(HEIGHT, (uint32)8) / 8, 1); endCommandBuffer(pCommandBuffer); } //output { pCommandBuffer = beginCommandBuffer(commandPool); imageBarrier( pCommandBuffer, image, VK_PIPELINE_STAGE_TOP_OF_PIPE_BIT, 0, VK_IMAGE_LAYOUT_GENERAL, VK_PIPELINE_STAGE_TRANSFER_BIT, VK_ACCESS_TRANSFER_READ_BIT, VK_IMAGE_LAYOUT_GENERAL); endCommandBuffer(pCommandBuffer); void* bufData; vkMapMemory(vulkanRHI_GetDevice(), imageMemory, 0, sizeof(FPixel)*WIDTH*HEIGHT, 0, &bufData); memcpy(pixels.data(), bufData, sizeof(FPixel)*WIDTH*HEIGHT); vkUnmapMemory(vulkanRHI_GetDevice(), imageMemory); pCommandBuffer = beginCommandBuffer(commandPool); imageBarrier( pCommandBuffer, image, VK_PIPELINE_STAGE_TRANSFER_BIT, VK_ACCESS_TRANSFER_READ_BIT, VK_IMAGE_LAYOUT_GENERAL, VK_PIPELINE_STAGE_TOP_OF_PIPE_BIT, 0, VK_IMAGE_LAYOUT_GENERAL); endCommandBuffer(pCommandBuffer); fstream file; file.open(("attempt_" + to_string(i) + ".txt").c_str(), ios::out); file << "\n\n\n"; for (int x = 0; x < 300; x++) { for (int y = 0; y < 300; y++) file << (pixels[x + y * WIDTH].r > 128 ? '+' : ' '); file << "\n"; } }
Compute shader just does same computation for every pixel. What I get:
You can see random holes which have size 8x8.
Shader code:
#version 450
#extension GL_ARB_separate_shader_objects : enable
layout(local_size_x = 8, local_size_y = 8) in;
layout(rgba8, binding = 3) uniform image2D ufmResultImage;
bool crossRaySphereOut(vec3 rayStart, vec3 rayDirection, vec3 sphereCenter, float sphereRadius, out vec3 result1, out vec3 result2)
{
vec3 rayPoint=rayStart+dot(sphereCenter-rayStart, rayDirection)*rayDirection;
float height=length(rayPoint-sphereCenter);
if(height<=sphereRadius)
{
float dist=sqrt(sphereRadius*sphereRadius-height*height);
result1=rayPoint-rayDirection*dist;
result2=rayPoint+rayDirection*dist;
return dot(result1-rayStart,rayDirection)>0.0f || dot(result2-rayStart,rayDirection)>0.0f;
}
return false;
}
bool crossRaySphereOutFar(vec3 rayStart, vec3 rayDirection, vec3 sphereCenter, float sphereRadius, out vec3 result)
{
vec3 tmpPoint;
return crossRaySphereOut(rayStart, rayDirection, sphereCenter, sphereRadius, tmpPoint, result);
}
float remap(float value, float minValue, float maxValue, float newMinValue, float newMaxValue)
{
return newMinValue+(value-minValue)/(maxValue-minValue)*(newMaxValue-newMinValue);
}
float cloudGetStepLength(vec3 position, float avrStep)
{
return avrStep;
}
float cloudGetHeight(vec3 position)
{
return clamp((length(position)-(6400+15))/((6400+35)-(6400+15)), 0, 1);
}
float cloudSampleDensity(vec3 position, float mip, bool fast)
{
float gc=1;
vec4 weather=vec4(1);
float wc0=weather.r;
float wc1=weather.g;
float wh=weather.b;
float wd=weather.a;
float ph=cloudGetHeight(position);
float WMc=max(wc0, clamp(gc-0.5, 0, 1)*wc1*2);
float SRb=clamp(remap(ph, 0, 0.07, 0, 1), 0, 1);
float SRt=clamp(remap(ph, wh*0.2, wh, 1, 0), 0, 1);
float SA=SRb*SRt;
float DRb=ph*clamp(remap(ph, 0, 0.15, 0, 1), 0, 1);
float DRt=ph*clamp(remap(ph, 0.9, 1, 1, 0), 0, 1);
float DA=DRb*DRt*wd*2;
float SNsample=1;
float d;
if(fast)
{
d=clamp(remap(SNsample*SA, 1-gc*WMc, 1, 0, 1), 0, 1)*DA;
}
else
{
float SNnd=clamp(remap(SNsample*SA, 1-gc*WMc, 1, 0, 1), 0, 1);
float DNfbm = 1;
float DNmod=0.35*exp(-gc*0.75)*mix(DNfbm, 1-DNfbm, clamp(ph*5, 0, 1));
d=clamp(remap(SNnd, DNmod, 1, 0, 1)*DA, 0, 1);
}
return d;
}
float cloudSampleSunDensity(vec3 position, vec3 sunDir, float mip)
{
float avrStep=((6400+35)-(6400+15));
float sumDensity=0;
float prevDensity=0;
for(int i=0;i<6;i++)
{
float step=cloudGetStepLength(position, avrStep);
position+=sunDir*step;
float density=cloudSampleDensity(position, mip, false);
float actualDensity=(density+prevDensity)*0.5;
prevDensity=density;
sumDensity+=actualDensity*step;
}
return sumDensity;
}
vec4 mainMarching(vec3 viewDir, vec3 sunDir, vec3 sunColor)
{
vec3 position;
crossRaySphereOutFar(vec3(0, 6400, 0), viewDir, vec3(0), (6400+15), position);
float avrStep=((6400+35)-(6400+15))/float(3/2);
position=position+viewDir*cloudGetStepLength(position, avrStep);
vec3 color=vec3(0);
float transmittance=1;
int zeroSamplesCount=0;
float sampleTest=0;
float step;
float prevDensity=0;
for(int i=0;i<160;i++)
{
if(sampleTest>0)
{
float density=cloudSampleDensity(position, 0, false);
float actualDensity=(density+prevDensity)*0.5;
prevDensity=density;
if(actualDensity>0)
{
float sunDensity=cloudSampleSunDensity(position, sunDir, 0);
vec3 light=15*sunColor*exp(-4*sunDensity)*(1-exp(-4*actualDensity*step));
light*=4*actualDensity;
color+=light*transmittance;
}
else
{
zeroSamplesCount++;
}
if(zeroSamplesCount<6)
{
step=cloudGetStepLength(position, avrStep);
position+=viewDir*step;
}
else
{
zeroSamplesCount=0;
sampleTest=0;
}
}
else
{
sampleTest=cloudSampleDensity(position, 0, true);
if(sampleTest<=0)
{
step=cloudGetStepLength(position, avrStep);
position+=viewDir*step;
}
}
if(transmittance<0.00001 || length(position)>(6400+35))
break;
}
return vec4(color*10, 1);
}
void main()
{
ivec2 g_id = ivec2(gl_GlobalInvocationID.x, gl_GlobalInvocationID.y);
if (g_id.x>=0 && g_id.x < 300 && g_id.y>=0 && g_id.y < 300)
{
vec3 viewDir=normalize(vec3(1,1,1));
vec3 sunDir= normalize(vec3(1,1,1));
vec3 sunColor=vec3(1,1,1);
imageStore(ufmResultImage, g_id, mainMarching(viewDir, sunDir, sunColor));
}
}
I have no idea what is going on. Looks like shader little bit complicated and somehow it gets access to wrong memory.
There was uninitialized variable in the shader. Anyway thank you for help.