GPU: StorageBuf: Add method to clear the buffer in place.

This is a faster way to clear a buffer instead of reuploading new data.
It is equivalent to `memset` and runs directly on the GPU.

This is better to clear huge buffers and to avoid the sync cost of data upload.

2 files changed, 26 insertions, 0 deletions

diff --git a/source/blender/gpu/opengl/gl_storage_buffer.cc b/source/blender/gpu/opengl/gl_storage_buffer.cc
index 12f942439ca..9cdde0b5734 100644
--- a/source/blender/gpu/opengl/gl_storage_buffer.cc
+++ b/source/blender/gpu/opengl/gl_storage_buffer.cc
@@ -112,6 +112,31 @@ void GLStorageBuf::unbind()
   slot_ = 0;
 }
 
+void GLStorageBuf::clear(eGPUTextureFormat internal_format, eGPUDataFormat data_format, void *data)
+{
+  if (ssbo_id_ == 0) {
+    this->init();
+  }
+
+  if (GLContext::direct_state_access_support) {
+    glClearNamedBufferData(ssbo_id_,
+                           to_gl_internal_format(internal_format),
+                           to_gl_data_format(internal_format),
+                           to_gl(data_format),
+                           data);
+  }
+  else {
+    /* WATCH(@fclem): This should be ok since we only use clear outside of drawing functions. */
+    glBindBuffer(GL_SHADER_STORAGE_BUFFER, ssbo_id_);
+    glClearBufferData(GL_SHADER_STORAGE_BUFFER,
+                      to_gl_internal_format(internal_format),
+                      to_gl_data_format(internal_format),
+                      to_gl(data_format),
+                      data);
+    glBindBuffer(GL_SHADER_STORAGE_BUFFER, 0);
+  }
+}
+
 /** \} */
 
 }  // namespace blender::gpu
diff --git a/source/blender/gpu/opengl/gl_storage_buffer.hh b/source/blender/gpu/opengl/gl_storage_buffer.hh
index 106d2158273..d657a4de09c 100644
--- a/source/blender/gpu/opengl/gl_storage_buffer.hh
+++ b/source/blender/gpu/opengl/gl_storage_buffer.hh
@@ -35,6 +35,7 @@ class GLStorageBuf : public StorageBuf {
   void update(const void *data) override;
   void bind(int slot) override;
   void unbind() override;
+  void clear(eGPUTextureFormat internal_format, eGPUDataFormat data_format, void *data) override;
 
  private:
   void init();