Gamma correction for output

3 files changed, 59 insertions, 9 deletions

diff --git a/BuddhaTest/include/Helpers.h b/BuddhaTest/include/Helpers.h
index a4bf15d..e4b7ffd 100644
--- a/BuddhaTest/include/Helpers.h
+++ b/BuddhaTest/include/Helpers.h
@@ -9,7 +9,7 @@ namespace Helpers
 	GLuint LoadShaders(const char * vertex_file_path, const char * fragment_file_path);

     GLuint LoadComputeShader(const char * compute_file_path, unsigned int localSizeX, unsigned int localSizeY, unsigned int localSizeZ);

 

-    void WriteOutputPNG(const std::vector<uint32_t>& data, unsigned int width, unsigned int bufferHeight);

+    void WriteOutputPNG(const std::vector<uint32_t>& data, unsigned int width, unsigned int bufferHeight, double gamma);

 

     /** Wraps around a C file descriptor. Libpng could be taught to use C++ streams, but I'm too lazy and rather wrap this ugly thing up, so it gets cleaned... */

     class ScopedCFileDescriptor

diff --git a/BuddhaTest/src/BuddhaTest.cpp b/BuddhaTest/src/BuddhaTest.cpp
index f23fc5d..9ac6ae3 100644
--- a/BuddhaTest/src/BuddhaTest.cpp
+++ b/BuddhaTest/src/BuddhaTest.cpp
@@ -11,8 +11,8 @@ void error_callback(int error, const char* description)
 

 int main()

 {

-    unsigned int bufferWidth = 1600;

-    unsigned int bufferHeight = 450;

+    unsigned int bufferWidth = 1920;

+    unsigned int bufferHeight = 540;

 

     unsigned int windowWidth = 1600;

     unsigned int windowHeight = 900;

@@ -29,6 +29,8 @@ int main()
     unsigned int globalWorkGroupSizeY = 1;

     unsigned int globalWorkGroupSizeZ = 1;

 

+    double pngGamma = 1.0;

+

 	GLFWwindow* window;

 

 	/* Initialize the library */

@@ -54,6 +56,49 @@ int main()
 	glfwMakeContextCurrent(window);

 	gladLoadGLLoader((GLADloadproc)glfwGetProcAddress);

 

+    //we have a context. Let's check if input is sane.

+    //calcualte buffer size, and make sure it's allowed by the driver.

+    const unsigned int pixelCount{(bufferWidth * bufferHeight)*3}; //*3 -> RGB

+    const unsigned int integerCount = pixelCount + 2; //first two elements in buffer: width/height.

+    {

+        int maxSSBOSize;

+        glGetIntegerv(GL_MAX_SHADER_STORAGE_BLOCK_SIZE,&maxSSBOSize);

+        if(integerCount * 4 > maxSSBOSize)

+        {

+            std::cout << "Requested buffer size larger than maximum allowed by graphics driver. Max pixel number: " << maxSSBOSize/12 - 2 << std::endl;

+            glfwTerminate();

+            return 0;

+        }

+        int WorkGroupSizeLimitX, WorkGroupSizeLimitY, WorkGroupSizeLimitZ;

+        glGetIntegeri_v(GL_MAX_COMPUTE_WORK_GROUP_COUNT,0,&WorkGroupSizeLimitX);

+        glGetIntegeri_v(GL_MAX_COMPUTE_WORK_GROUP_COUNT,1,&WorkGroupSizeLimitY);

+        glGetIntegeri_v(GL_MAX_COMPUTE_WORK_GROUP_COUNT,2,&WorkGroupSizeLimitZ);

+        if(globalWorkGroupSizeX > WorkGroupSizeLimitX || globalWorkGroupSizeY > WorkGroupSizeLimitY || globalWorkGroupSizeZ > WorkGroupSizeLimitZ)

+        {

+            std::cout << "Requested global work group size exceeds maximum dimension. Limits: " << WorkGroupSizeLimitX << ", " << WorkGroupSizeLimitY << ", " << WorkGroupSizeLimitZ << std::endl;

+            glfwTerminate();

+            return 0;

+        }

+        glGetIntegeri_v(GL_MAX_COMPUTE_WORK_GROUP_SIZE,0,&WorkGroupSizeLimitX);

+        glGetIntegeri_v(GL_MAX_COMPUTE_WORK_GROUP_SIZE,1,&WorkGroupSizeLimitY);

+        glGetIntegeri_v(GL_MAX_COMPUTE_WORK_GROUP_SIZE,2,&WorkGroupSizeLimitZ);

+        if(localWorkgroupSizeX > WorkGroupSizeLimitX || localWorkgroupSizeY > WorkGroupSizeLimitY || localWorkgroupSizeZ > WorkGroupSizeLimitZ)

+        {

+            std::cout << "Requested local work group size exceeds maximum dimension. Limits: " << WorkGroupSizeLimitX << ", " << WorkGroupSizeLimitY << ", " << WorkGroupSizeLimitZ << std::endl;

+            glfwTerminate();

+            return 0;

+        }

+        int maxInvocations;

+        glGetIntegerv(GL_MAX_COMPUTE_WORK_GROUP_INVOCATIONS,&maxInvocations);

+        if(localWorkgroupSizeX*localWorkgroupSizeY*localWorkgroupSizeZ > maxInvocations)

+        {

+            std::cout << "Requested local work group size exceeds maximum total count (Product of x*y*z dimensions). Limit: " << maxInvocations << std::endl;

+            glfwTerminate();

+            return 0;

+        }

+    }

+

+

 	GLuint VertexArrayID;

 	glGenVertexArrays(1, &VertexArrayID);

 	glBindVertexArray(VertexArrayID);

@@ -75,8 +120,6 @@ int main()
 	glGenBuffers(1, &drawBuffer);

 	glBindBuffer(GL_SHADER_STORAGE_BUFFER, drawBuffer);

     {

-        const unsigned int pixelCount{(bufferWidth * bufferHeight)*3}; //*3 -> RGB

-        const unsigned int integerCount = pixelCount + 2; //first two elements in buffer: width/height.

         std::vector<uint32_t> initializeBuffer(integerCount,0);

         initializeBuffer[0] = bufferWidth;

         initializeBuffer[1] = bufferHeight;

@@ -138,10 +181,9 @@ int main()
     glMemoryBarrier(GL_ALL_BARRIER_BITS);

     glBindBuffer(GL_SHADER_STORAGE_BUFFER, drawBuffer);

     {

-        const unsigned int pixelCount{(bufferWidth * bufferHeight)*3}; //*3 -> RGB

         std::vector<uint32_t> readBackBuffer(pixelCount);

         glGetBufferSubData(GL_SHADER_STORAGE_BUFFER,4*2,4 * pixelCount,readBackBuffer.data()); //offset of 2*4, that's the dimension integers.

-        Helpers::WriteOutputPNG(readBackBuffer,bufferWidth,bufferHeight);

+        Helpers::WriteOutputPNG(readBackBuffer,bufferWidth,bufferHeight, pngGamma);

     }

 

     //a bit of cleanup

diff --git a/BuddhaTest/src/Helpers.cpp b/BuddhaTest/src/Helpers.cpp
index 881d01f..bde6b8a 100644
--- a/BuddhaTest/src/Helpers.cpp
+++ b/BuddhaTest/src/Helpers.cpp
@@ -5,6 +5,7 @@
 #include <iostream>

 #include <vector>

 #include <png.h>

+#include <cmath>

 

 namespace Helpers

 {

@@ -154,7 +155,7 @@ namespace Helpers
 		return ProgramID;

 	}

 

-    void WriteOutputPNG(const std::vector<uint32_t>& data, unsigned int width, unsigned int bufferHeight)

+    void WriteOutputPNG(const std::vector<uint32_t>& data, unsigned int width, unsigned int bufferHeight, double gamma)

     {

         std::vector<png_byte> pngData(3*width*2*bufferHeight);

         std::vector<png_byte *> rows{2*bufferHeight};

@@ -170,7 +171,14 @@ namespace Helpers
         }

         for(unsigned int i = 0; i < data.size();++i)

         {

-            pngData[data.size() + i] = (255*data[i] + (maxValue/2))/maxValue;

+            if(fabs(gamma - 1.0) > 0.0001)

+            {

+                pngData[data.size() + i] = 255.0 * pow(static_cast<double>(data[i])/static_cast<double>(maxValue),gamma);

+            }

+            else

+            {

+                pngData[data.size() + i] = (255*data[i] + (maxValue/2))/maxValue;

+            }

         }

         for(int i = 0; i < bufferHeight;++i)

         {