From 7ee816e32f3655d4ca8abb555f885d8de9ba0520 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Foucault?= <foucault.clem@gmail.com>
Date: Wed, 16 Mar 2022 08:42:12 +0100
Subject: 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.
---
 source/blender/gpu/GPU_storage_buffer.h            |  7 ++++++
 source/blender/gpu/intern/gpu_storage_buffer.cc    | 14 ++++++++++++
 .../gpu/intern/gpu_storage_buffer_private.hh       |  3 +++
 source/blender/gpu/opengl/gl_storage_buffer.cc     | 25 ++++++++++++++++++++++
 source/blender/gpu/opengl/gl_storage_buffer.hh     |  1 +
 5 files changed, 50 insertions(+)

(limited to 'source/blender')

diff --git a/source/blender/gpu/GPU_storage_buffer.h b/source/blender/gpu/GPU_storage_buffer.h
index 930b6a1012b..1478d490e23 100644
--- a/source/blender/gpu/GPU_storage_buffer.h
+++ b/source/blender/gpu/GPU_storage_buffer.h
@@ -13,6 +13,7 @@
 
 #pragma once
 
+#include "GPU_texture.h"
 #include "GPU_vertex_buffer.h"
 
 #ifdef __cplusplus
@@ -40,6 +41,12 @@ void GPU_storagebuf_bind(GPUStorageBuf *ssbo, int slot);
 void GPU_storagebuf_unbind(GPUStorageBuf *ssbo);
 void GPU_storagebuf_unbind_all(void);
 
+void GPU_storagebuf_clear(GPUStorageBuf *ssbo,
+                          eGPUTextureFormat internal_format,
+                          eGPUDataFormat data_format,
+                          void *data);
+void GPU_storagebuf_clear_to_zero(GPUStorageBuf *ssbo);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/source/blender/gpu/intern/gpu_storage_buffer.cc b/source/blender/gpu/intern/gpu_storage_buffer.cc
index 3ea0bef5403..806acad90fe 100644
--- a/source/blender/gpu/intern/gpu_storage_buffer.cc
+++ b/source/blender/gpu/intern/gpu_storage_buffer.cc
@@ -89,4 +89,18 @@ void GPU_storagebuf_unbind_all()
   /* FIXME */
 }
 
+void GPU_storagebuf_clear(GPUStorageBuf *ssbo,
+                          eGPUTextureFormat internal_format,
+                          eGPUDataFormat data_format,
+                          void *data)
+{
+  unwrap(ssbo)->clear(internal_format, data_format, data);
+}
+
+void GPU_storagebuf_clear_to_zero(GPUStorageBuf *ssbo)
+{
+  uint32_t data = 0u;
+  GPU_storagebuf_clear(ssbo, GPU_R32UI, GPU_DATA_UINT, &data);
+}
+
 /** \} */
diff --git a/source/blender/gpu/intern/gpu_storage_buffer_private.hh b/source/blender/gpu/intern/gpu_storage_buffer_private.hh
index e97f3eba697..06e7c2c0e9d 100644
--- a/source/blender/gpu/intern/gpu_storage_buffer_private.hh
+++ b/source/blender/gpu/intern/gpu_storage_buffer_private.hh
@@ -40,6 +40,9 @@ class StorageBuf {
   virtual void update(const void *data) = 0;
   virtual void bind(int slot) = 0;
   virtual void unbind() = 0;
+  virtual void clear(eGPUTextureFormat internal_format,
+                     eGPUDataFormat data_format,
+                     void *data) = 0;
 };
 
 /* Syntactic sugar. */
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();
-- 
cgit v1.2.3