OpenGL: Optimize out unnecessary query for buffer size

jspanchu · jspanchu · commit d75b9ab60ad4 · 2023-10-27T13:20:42.000-04:00
- Adds a new method to retrieve the size of allocation of an OpenGL
buffer object
diff --git a/Rendering/OpenGL2/vtkOpenGLBufferObject.cxx b/Rendering/OpenGL2/vtkOpenGLBufferObject.cxx
@@ -61,10 +61,12 @@ struct vtkOpenGLBufferObject::Private
     this->Handle = 0;
     this->Type = GL_ARRAY_BUFFER;
     this->Usage = GL_STATIC_DRAW;
+    this->Size = 0;
   }
   GLenum Type;
   GLenum Usage;
   GLuint Handle;
+  size_t Size;
 };
 
 vtkOpenGLBufferObject::vtkOpenGLBufferObject()
@@ -164,9 +166,15 @@ bool vtkOpenGLBufferObject::Allocate(size_t size, ObjectType objectType, ObjectU
   glBufferData(
     this->Internal->Type, static_cast<GLsizeiptr>(size), nullptr, convertUsage(objectUsage));
   this->Dirty = true;
+  this->Internal->Size = size;
   return true;
 }
 
+size_t vtkOpenGLBufferObject::GetSize()
+{
+  return this->Internal->Size;
+}
+
 bool vtkOpenGLBufferObject::Bind()
 {
   if (!this->Internal->Handle)
diff --git a/Rendering/OpenGL2/vtkOpenGLBufferObject.h b/Rendering/OpenGL2/vtkOpenGLBufferObject.h
@@ -92,6 +92,12 @@ class VTKRENDERINGOPENGL2_EXPORT vtkOpenGLBufferObject : public vtkObject
    * Allocates a buffer of `type` with `size` bytes.
    */
   bool Allocate(size_t size, ObjectType type, ObjectUsage usage);
+
+  /**
+   * Get size of the buffer in bytes.
+   */
+  size_t GetSize();
+
   /**
    * Bind the buffer object ready for rendering.
    * @note Only one ARRAY_BUFFER and one ELEMENT_ARRAY_BUFFER may be bound at
diff --git a/Rendering/OpenGL2/vtkTextureObject.cxx b/Rendering/OpenGL2/vtkTextureObject.cxx
@@ -1179,6 +1179,7 @@ bool vtkTextureObject::Create1DFromRaw(unsigned int width, int numComps, int dat
 // Description:
 // Create a texture buffer basically a 1D texture that can be
 // very large for passing data into the fragment shader
+//------------------------------------------------------------------------------
 bool vtkTextureObject::CreateTextureBuffer(
   unsigned int numValues, int numComps, int dataType, vtkOpenGLBufferObject* bo)
 {
@@ -1215,11 +1216,7 @@ bool vtkTextureObject::EmulateTextureBufferWith2DTextures(
     {
       srcTarget = GL_ELEMENT_ARRAY_BUFFER;
     }
-    GLint64 srcNumBytes = 0;
     bo->Bind();
-    glGetBufferParameteri64v(srcTarget, GL_BUFFER_SIZE, &srcNumBytes);
-    vtkOpenGLCheckErrors("glGetBufferParameteri64v ");
-
     // issue 3 (https://registry.khronos.org/OpenGL/extensions/ARB/ARB_pixel_buffer_object.txt)
     // says it's alright to bind any b.o (GL_ARRAY_BUFFER, etc) to unpacked buffer
     // and go ahead with glTexImage,
@@ -1230,11 +1227,12 @@ bool vtkTextureObject::EmulateTextureBufferWith2DTextures(
     pbo->Allocate(dataType, width * height, numComps, vtkPixelBufferObject::UNPACKED_BUFFER);
     pbo->BindToUnPackedBuffer();
     // transfers within gpu memory space on most GL driver implementations.
-    glCopyBufferSubData(srcTarget, dstTarget, 0, 0, srcNumBytes);
+    glCopyBufferSubData(srcTarget, dstTarget, 0, 0, bo->GetSize());
     vtkOpenGLCheckErrors("glCopyBufferSubData ");
 
+    // Get rid of the original buffer data
+    bo->ReleaseGraphicsResources();
     // unbind
-    bo->Release();
     pbo->UnBind();
 
     // source a 2D texture with the pbo.
