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, 13 insertions, 1 deletions

diff --git a/source/blender/editors/include/ED_view3d.h b/source/blender/editors/include/ED_view3d.h
index 5514dc0d3df..af6f37d937c 100644
--- a/source/blender/editors/include/ED_view3d.h
+++ b/source/blender/editors/include/ED_view3d.h
@@ -302,7 +302,19 @@ bool ED_view3d_autodist_depth_seg(struct ARegion *ar, const int mval_sta[2], con
 /* select */
 #define MAXPICKELEMS    2500
 #define MAXPICKBUF      (4 * MAXPICKELEMS)
-short view3d_opengl_select(struct ViewContext *vc, unsigned int *buffer, unsigned int bufsize, const struct rcti *input, bool do_nearest);
+
+enum {
+	/* all elements in the region, ignore depth */
+	VIEW3D_SELECT_ALL = 0,
+	/* pick also depth sorts (only for small regions!) */
+	VIEW3D_SELECT_PICK_ALL = 1,
+	/* sorts and only returns visible objects (only for small regions!) */
+	VIEW3D_SELECT_PICK_NEAREST = 2,
+};
+
+int view3d_opengl_select(
+        struct ViewContext *vc, unsigned int *buffer, unsigned int bufsize, const struct rcti *input,
+        int select_mode);
 
 /* view3d_select.c */
 float ED_view3d_select_dist_px(void);