3D View: new nethod of opengl selection

Intended to replace legacy GL_SELECT, without the limitations of
sample queries which can't access depth information.

This commit adds VIEW3D_SELECT_PICK_NEAREST and VIEW3D_SELECT_PICK_ALL
which access the depth buffers to detect whats under the pointer,
so initial selection is always the closest item.

The performance of this method depends a lot on the OpenGL
implementations glReadPixels.

Since reading depth can be slow, buffers are cached for object picking
so selecting re-uses depth data, performing 1 draw instead of 3
(for 24, 18, 10 px regions, picking with many items under the pointer).

Occlusion queries draw twice when picking nearest,
so worst case 6x draw calls per selection.

Even with these improvements occlusion queries is faster on AMD hardware.

Depth selection is disabled by default, toggle option under select method.
May enable by default if this works well on different hardware.

Reviewed as D2543

1 files changed, 10 insertions, 0 deletions

diff --git a/source/blender/gpu/GPU_select.h b/source/blender/gpu/GPU_select.h
index 93f5ce13bbd..cf5b8bf7d8f 100644
--- a/source/blender/gpu/GPU_select.h
+++ b/source/blender/gpu/GPU_select.h
@@ -37,8 +37,12 @@ struct rcti;
 /* flags for mode of operation */
 enum {
 	GPU_SELECT_ALL                      = 1,
+	/* gpu_select_query */
 	GPU_SELECT_NEAREST_FIRST_PASS       = 2,
 	GPU_SELECT_NEAREST_SECOND_PASS      = 3,
+	/* gpu_select_pick */
+	GPU_SELECT_PICK_ALL           = 4,
+	GPU_SELECT_PICK_NEAREST       = 5,
 };
 
 void GPU_select_begin(unsigned int *buffer, unsigned int bufsize, const struct rcti *input, char mode, int oldhits);
@@ -46,4 +50,10 @@ bool GPU_select_load_id(unsigned int id);
 unsigned int GPU_select_end(void);
 bool GPU_select_query_check_active(void);
 
+/* cache selection region */
+bool GPU_select_is_cached(void);
+void GPU_select_cache_begin(void);
+void GPU_select_cache_load_id(void);
+void GPU_select_cache_end(void);
+
 #endif