Fix memory allocation for state buffer. How could that ever work?

2 files changed, 11 insertions, 2 deletions

diff --git a/BuddhaTest/Shaders/BuddhaCompute.glsl b/BuddhaTest/Shaders/BuddhaCompute.glsl
index 61bbb6d..5998d6e 100644
--- a/BuddhaTest/Shaders/BuddhaCompute.glsl
+++ b/BuddhaTest/Shaders/BuddhaCompute.glsl
@@ -15,6 +15,7 @@ layout(std430, binding=4) restrict buffer renderedDataBlue
     restrict uint counts_SSBOBlue[];
 };
 
+layout(packed)
 struct individualData
 {
     uint phase;
@@ -23,7 +24,7 @@ struct individualData
     vec2 lastPosition;
 };
 
-layout(std430, binding=5) restrict buffer statusBuffer
+layout(packed, binding=5) restrict buffer statusBuffer
 {
     restrict individualData state[];
 };
diff --git a/BuddhaTest/src/BuddhaTest.cpp b/BuddhaTest/src/BuddhaTest.cpp
index 95bd22f..20bd1ac 100644
--- a/BuddhaTest/src/BuddhaTest.cpp
+++ b/BuddhaTest/src/BuddhaTest.cpp
@@ -124,11 +124,19 @@ int main(int argc, char * argv[])
     }
     glBindBuffer(GL_SHADER_STORAGE_BUFFER, 0);
 
+    //the state buffer is special. While making each entry 8 bytes large and using std430 layout, the data is never read back,
+    //so we can get away with being more lenient and allowing the compiler to choose layout without much extra work.
+    //We need to query the size for allocation though.
+    GLuint stateBufferIndex = glGetProgramResourceIndex(ComputeShader,GL_SHADER_STORAGE_BLOCK,"statusBuffer");
+    GLint requiredStateBufferSizePerWorker;
+    GLenum t = GL_BUFFER_DATA_SIZE;
+    glGetProgramResourceiv(ComputeShader,GL_SHADER_STORAGE_BLOCK,stateBufferIndex,1,&t,1,nullptr,&requiredStateBufferSizePerWorker);
+
     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*(7*workersPerFrame),nullptr,GL_DYNAMIC_COPY);
+    glBufferData(GL_SHADER_STORAGE_BUFFER, requiredStateBufferSizePerWorker*workersPerFrame,nullptr,GL_DYNAMIC_COPY);
     glClearBufferData(GL_SHADER_STORAGE_BUFFER,GL_R8,GL_RED,GL_UNSIGNED_INT,nullptr);
     glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 5, stateBuffer);