GPUBatch: Add GPU_batch_draw_indirect

This allows rendering a batch with parameters computed by the GPU.

Contains GL backend implementation.

5 files changed, 43 insertions, 1 deletions

diff --git a/source/blender/gpu/GPU_batch.h b/source/blender/gpu/GPU_batch.h
index 7fad8dd23be..7ef2d81ac31 100644
--- a/source/blender/gpu/GPU_batch.h
+++ b/source/blender/gpu/GPU_batch.h
@@ -14,6 +14,7 @@
 
 #include "GPU_index_buffer.h"
 #include "GPU_shader.h"
+#include "GPU_storage_buffer.h"
 #include "GPU_uniform_buffer.h"
 #include "GPU_vertex_buffer.h"
 
@@ -171,7 +172,13 @@ void GPU_batch_draw_instanced(GPUBatch *batch, int i_count);
 /**
  * This does not bind/unbind shader and does not call GPU_matrix_bind().
  */
-void GPU_batch_draw_advanced(GPUBatch *, int v_first, int v_count, int i_first, int i_count);
+void GPU_batch_draw_advanced(GPUBatch *batch, int v_first, int v_count, int i_first, int i_count);
+
+/**
+ * Issue a draw call using GPU computed arguments. The argument are expected to be valid for the
+ * type of geometry drawn (index or non-indexed).
+ */
+void GPU_batch_draw_indirect(GPUBatch *batch, GPUStorageBuf *indirect_buf);
 
 #if 0 /* future plans */
 
diff --git a/source/blender/gpu/intern/gpu_batch.cc b/source/blender/gpu/intern/gpu_batch.cc
index 1b34b6e6c69..0b47a7b2952 100644
--- a/source/blender/gpu/intern/gpu_batch.cc
+++ b/source/blender/gpu/intern/gpu_batch.cc
@@ -270,6 +270,15 @@ void GPU_batch_draw_advanced(
   batch->draw(v_first, v_count, i_first, i_count);
 }
 
+void GPU_batch_draw_indirect(GPUBatch *gpu_batch, GPUStorageBuf *indirect_buf)
+{
+  BLI_assert(Context::get()->shader != nullptr);
+  BLI_assert(indirect_buf != nullptr);
+  Batch *batch = static_cast<Batch *>(gpu_batch);
+
+  batch->draw_indirect(indirect_buf);
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */
diff --git a/source/blender/gpu/intern/gpu_batch_private.hh b/source/blender/gpu/intern/gpu_batch_private.hh
index 23052f601d2..8ca19884fd7 100644
--- a/source/blender/gpu/intern/gpu_batch_private.hh
+++ b/source/blender/gpu/intern/gpu_batch_private.hh
@@ -29,6 +29,7 @@ class Batch : public GPUBatch {
   virtual ~Batch() = default;
 
   virtual void draw(int v_first, int v_count, int i_first, int i_count) = 0;
+  virtual void draw_indirect(GPUStorageBuf *indirect_buf) = 0;
 
   /* Convenience casts. */
   IndexBuf *elem_() const
diff --git a/source/blender/gpu/opengl/gl_batch.cc b/source/blender/gpu/opengl/gl_batch.cc
index fde2a53bb0f..4ec86b98cbe 100644
--- a/source/blender/gpu/opengl/gl_batch.cc
+++ b/source/blender/gpu/opengl/gl_batch.cc
@@ -18,6 +18,7 @@
 #include "gl_debug.hh"
 #include "gl_index_buffer.hh"
 #include "gl_primitive.hh"
+#include "gl_storage_buffer.hh"
 #include "gl_vertex_array.hh"
 
 #include "gl_batch.hh"
@@ -326,4 +327,27 @@ void GLBatch::draw(int v_first, int v_count, int i_first, int i_count)
   }
 }
 
+void GLBatch::draw_indirect(GPUStorageBuf *indirect_buf)
+{
+  GL_CHECK_RESOURCES("Batch");
+
+  this->bind(0);
+
+  dynamic_cast<GLStorageBuf *>(unwrap(indirect_buf))->bind_as(GL_DRAW_INDIRECT_BUFFER);
+  /* This barrier needs to be here as it only work on the currently bound indirect buffer. */
+  glMemoryBarrier(GL_COMMAND_BARRIER_BIT);
+
+  GLenum gl_type = to_gl(prim_type);
+  if (elem) {
+    const GLIndexBuf *el = this->elem_();
+    GLenum index_type = to_gl(el->index_type_);
+    glDrawElementsIndirect(gl_type, index_type, (GLvoid *)nullptr);
+  }
+  else {
+    glDrawArraysIndirect(gl_type, (GLvoid *)nullptr);
+  }
+  /* Unbind. */
+  glBindBuffer(GL_DRAW_INDIRECT_BUFFER, 0);
+}
+
 /** \} */
diff --git a/source/blender/gpu/opengl/gl_batch.hh b/source/blender/gpu/opengl/gl_batch.hh
index 1a18572c683..bb53d9b31f1 100644
--- a/source/blender/gpu/opengl/gl_batch.hh
+++ b/source/blender/gpu/opengl/gl_batch.hh
@@ -93,6 +93,7 @@ class GLBatch : public Batch {
 
  public:
   void draw(int v_first, int v_count, int i_first, int i_count) override;
+  void draw_indirect(GPUStorageBuf *indirect_buf) override;
   void bind(int i_first);
 
   /* Convenience getters. */