From a350181f2c15feb072c2edf5d0c41965936f1948 Mon Sep 17 00:00:00 2001
From: Andreas Grois <andi@grois.info>
Date: Wed, 14 Mar 2018 22:39:06 +0100
Subject: First commit with compute pausability

---
 BuddhaTest/src/BuddhaTest.cpp | 45 +++++++++++++++++++++++++++++++------------
 1 file changed, 33 insertions(+), 12 deletions(-)

(limited to 'BuddhaTest/src/BuddhaTest.cpp')

diff --git a/BuddhaTest/src/BuddhaTest.cpp b/BuddhaTest/src/BuddhaTest.cpp
index 5d03ad4..fcc76a3 100644
--- a/BuddhaTest/src/BuddhaTest.cpp
+++ b/BuddhaTest/src/BuddhaTest.cpp
@@ -122,15 +122,27 @@ int main(int argc, char * argv[])
     }
     glBindBuffer(GL_SHADER_STORAGE_BUFFER, 0);
 
+    const uint32_t workersPerFrame = settings.globalWorkGroupSizeX*settings.globalWorkGroupSizeY*settings.globalWorkGroupSizeZ*settings.localWorkgroupSizeX*settings.localWorkgroupSizeY*settings.localWorkgroupSizeZ;
+    GLuint stateBuffer;
+    glGenBuffers(1,&stateBuffer);
+    glBindBuffer(GL_SHADER_STORAGE_BUFFER,stateBuffer);
+    glBufferData(GL_SHADER_STORAGE_BUFFER, 4*(4*workersPerFrame+1),nullptr,GL_DYNAMIC_COPY);
+    glClearBufferData(GL_SHADER_STORAGE_BUFFER,GL_R8,GL_RED,GL_UNSIGNED_INT,nullptr);
+    glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 5, stateBuffer);
+
     uint32_t iterationCount{0};
     glUseProgram(ComputeShader);
     GLint iterationCountUniformHandle = glGetUniformLocation(ComputeShader, "iterationCount");
     GLint orbitLengthUniformHandle = glGetUniformLocation(ComputeShader, "orbitLength");
     GLint widthUniformComputeHandle = glGetUniformLocation(ComputeShader, "width");
     GLint heightUniformComputeHandle = glGetUniformLocation(ComputeShader, "height");
+    GLint iterationChangedHandle = glGetUniformLocation(ComputeShader, "iterationChanged");
+    GLint iterationsPerDispatchHandle = glGetUniformLocation(ComputeShader, "iterationsPerDispatch");
     glUniform3ui(orbitLengthUniformHandle,settings.orbitLengthRed,settings.orbitLengthGreen,settings.orbitLengthBlue);
     glUniform1ui(widthUniformComputeHandle, settings.imageWidth);
     glUniform1ui(heightUniformComputeHandle, bufferHeight);
+    glUniform1ui(iterationChangedHandle,1);
+    glUniform1ui(iterationsPerDispatchHandle, settings.iterationsPerFrame);
 
     glUseProgram(VertexAndFragmentShaders);
     GLint widthUniformFragmentHandle = glGetUniformLocation(VertexAndFragmentShaders, "width");
@@ -140,29 +152,37 @@ int main(int argc, char * argv[])
 
     glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
 
-    //uint32_t iterationsPerFrame = settings.globalWorkGroupSizeX*settings.globalWorkGroupSizeY*settings.globalWorkGroupSizeZ*settings.localWorkgroupSizeX*settings.localWorkgroupSizeY*settings.localWorkgroupSizeZ;
-    //bool bWarningShown{false};
-
 	/* Loop until the user closes the window */
 	while (!glfwWindowShouldClose(window))
 	{
-        //commented out, as with the new y-decoupling we will get more points in 2D even after we had all integer values for x.
-        //check if we are "done"
-        //if(iterationsPerFrame * iterationCount <= iterationsPerFrame && iterationCount > 1 && !bWarningShown)
-        //{
-        //    std::cout << "The program covered all possible integer values for starting point computation. Leaving it running will not improve the image any more." << std::endl;
-        //    bWarningShown = true;
-        //}
+        //clear first integer in state buffer. That's the "boolean" we use to determine if we should increment iterationCount.
+        glBindBuffer(GL_SHADER_STORAGE_BUFFER,stateBuffer);
+        glClearBufferSubData(GL_SHADER_STORAGE_BUFFER,GL_R8,0,4,GL_RED,GL_UNSIGNED_INT,nullptr);
 
 		//let the compute shader do something
 		glUseProgram(ComputeShader);
-        //increase iterationCount, which is used for pseudo random generation
-        glUniform1ui(iterationCountUniformHandle,++iterationCount);
+        //set iterationCount, which is used for pseudo random generation
+        glUniform1ui(iterationCountUniformHandle,iterationCount);
         glDispatchCompute(settings.globalWorkGroupSizeX, settings.globalWorkGroupSizeY, settings.globalWorkGroupSizeZ);
 
         //before reading the values in the ssbo, we need a memory barrier:
         glMemoryBarrier(GL_SHADER_STORAGE_BARRIER_BIT); //I hope this is the correct (and only required) bit
 
+        //read back first bit of state buffer. If it's zero, increment iterationcount and set glUniform1ui(iterationChangedHandle,1);
+        //if it's nonzero set glUniform1ui(iterationChangedHandle,0);
+        glBindBuffer(GL_SHADER_STORAGE_BUFFER,stateBuffer);
+        uint accumulatedState;
+        glGetBufferSubData(GL_SHADER_STORAGE_BUFFER,0,4,&accumulatedState);
+        if(accumulatedState)
+        {
+            glUniform1ui(iterationChangedHandle,0);
+        }
+        else
+        {
+            glUniform1ui(iterationChangedHandle,1);
+            ++iterationCount;
+        }
+
 		/* Render here */
 		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 		glUseProgram(VertexAndFragmentShaders);
@@ -210,6 +230,7 @@ int main(int argc, char * argv[])
     //a bit of cleanup
     glDeleteBuffers(1,&vertexbuffer);
     glDeleteBuffers(3,drawBuffer);
+    glDeleteBuffers(1,&stateBuffer);
 
 	glfwTerminate();
 	return 0;
-- 
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