Occlusion Query based selection.

This patch creates an interface for selection mechanisms in opengl. This
makes it possible to switch between occlusion query based or select
rendermode based selection transparently.

This is really useful on graphics drivers that do not accelerate the
select rendermode path (some ATI cards are notorious for this, and the
new path is used by default there), since occlusion queries are always
hardware accelerated due to their use in games.

The option can be found under system - selection. Auto just enables
occlusion queries for ATI users while the rest of the options enforce
one of the two methods always.

There is just one known change, previous code enforced nearest bone to
always get selected, even when mouse selecting near the same position, I
couldn't replicate the behaviour though.

patch by me with edits and review by Campbell.

Thanks!

3 files changed, 309 insertions, 0 deletions

diff --git a/source/blender/gpu/CMakeLists.txt b/source/blender/gpu/CMakeLists.txt
index 739deffa519..13e46bc7de8 100644
--- a/source/blender/gpu/CMakeLists.txt
+++ b/source/blender/gpu/CMakeLists.txt
@@ -51,12 +51,14 @@ set(SRC
 	intern/gpu_extensions.c
 	intern/gpu_material.c
 	intern/gpu_simple_shader.c
+	intern/gpu_select.c
 
 	GPU_buffers.h
 	GPU_draw.h
 	GPU_extensions.h
 	GPU_material.h
 	GPU_simple_shader.h
+	GPU_select.h
 	intern/gpu_codegen.h
 )
 
diff --git a/source/blender/gpu/GPU_select.h b/source/blender/gpu/GPU_select.h
new file mode 100644
index 00000000000..1a274e0ad9d
--- /dev/null
+++ b/source/blender/gpu/GPU_select.h
@@ -0,0 +1,61 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2014 Blender Foundation.
+ * All rights reserved.
+ *
+ * Contributor(s): Antony Riakiotakis.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file GPU_select.h
+ *  \ingroup gpu
+ */
+
+#ifndef __GPU_SELECT__
+#define __GPU_SELECT__
+
+#include "DNA_vec_types.h"  /* rcft */
+#include "BLI_sys_types.h"
+
+/* flags for mode of operation */
+enum {
+	GPU_SELECT_ALL                      = 1,
+	GPU_SELECT_NEAREST_FIRST_PASS       = 2,
+	GPU_SELECT_NEAREST_SECOND_PASS      = 3,
+};
+
+/* initialize and provide buffer for results */
+void GPU_select_begin(unsigned int *buffer, unsigned int bufsize, rctf *input, char mode, int oldhits);
+
+/* loads a new selection id and ends previous query, if any. In second pass of selection it also returns
+ * if id has been hit on the first pass already. Thus we can skip drawing un-hit objects IMPORTANT: We rely on the order of object rendering on passes to be
+ * the same for this to work */
+bool GPU_select_load_id(unsigned int id);
+
+/* cleanup and flush selection results to buffer. Return number of hits and hits in buffer.
+ * if dopass is true, we will do a second pass with occlusion queries to get the closest hit */
+unsigned int GPU_select_end(void);
+
+/* does the GPU support occlusion queries? */
+bool GPU_select_query_check_support(void);
+
+/* is occlusion query supported and user activated? */
+bool GPU_select_query_check_active(void);
+
+#endif
diff --git a/source/blender/gpu/intern/gpu_select.c b/source/blender/gpu/intern/gpu_select.c
new file mode 100644
index 00000000000..2df9e603903
--- /dev/null
+++ b/source/blender/gpu/intern/gpu_select.c
@@ -0,0 +1,246 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2014 Blender Foundation.
+ * All rights reserved.
+ *
+ * Contributor(s): Antony Riakiotakis.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file blender/gpu/intern/gpu_select.c
+ *  \ingroup gpu
+ *
+ * Interface for accessing gpu-related methods for selection. The semantics will be
+ * similar to glRenderMode(GL_SELECT) since the goal is to maintain compatibility.
+ */
+#include "GPU_select.h"
+#include "GPU_extensions.h"
+
+#include "BLI_utildefines.h"
+
+#include "MEM_guardedalloc.h"
+
+#include "DNA_userdef_types.h"
+
+#include <GL/glew.h>
+
+/* Ad hoc number of queries to allocate to skip doing many glGenQueries */
+#define ALLOC_QUERIES 200
+
+typedef struct GPUQueryState {
+	/* To ignore selection id calls when not initialized */
+	bool select_is_active;
+	/* Tracks whether a query has been issued so that gpu_load_id can end the previous one */
+	bool query_issued;
+	/* array holding the OpenGL query identifiers */
+	unsigned int *queries;
+	/* array holding the id corresponding to each query */
+	unsigned int *id;
+	/* number of queries in *queries and *id */
+	unsigned int num_of_queries;
+	/* index to the next query to start */
+	unsigned int active_query;
+	/* flag to cache user preference for occlusion based selection */
+	bool use_gpu_select;
+	/* cache on initialization */
+	unsigned int *buffer;
+	unsigned int bufsize;
+	/* mode of operation */
+	char mode;
+	unsigned int index;
+	int oldhits;
+} GPUQueryState;
+
+static GPUQueryState g_query_state = {0};
+
+void GPU_select_begin(unsigned int *buffer, unsigned int bufsize, rctf *input, char mode, int oldhits)
+{
+	g_query_state.select_is_active = true;
+	g_query_state.query_issued = false;
+	g_query_state.active_query = 0;
+	g_query_state.use_gpu_select = GPU_select_query_check_active();
+	g_query_state.num_of_queries = 0;
+	g_query_state.bufsize = bufsize;
+	g_query_state.buffer = buffer;
+	g_query_state.mode = mode;
+	g_query_state.index = 0;
+	g_query_state.oldhits = oldhits;
+
+	if (!g_query_state.use_gpu_select) {
+		glSelectBuffer( bufsize, (GLuint *)buffer);
+		glRenderMode(GL_SELECT);
+		glInitNames();
+		glPushName(-1);
+	}
+	else {
+		float viewport[4];
+
+		g_query_state.num_of_queries = ALLOC_QUERIES;
+
+		g_query_state.queries = MEM_mallocN(g_query_state.num_of_queries * sizeof(*g_query_state.queries) , "gpu selection queries");
+		g_query_state.id = MEM_mallocN(g_query_state.num_of_queries * sizeof(*g_query_state.id) , "gpu selection ids");
+		glGenQueriesARB(g_query_state.num_of_queries, g_query_state.queries);
+
+		glPushAttrib(GL_DEPTH_BUFFER_BIT | GL_VIEWPORT_BIT);
+		/* disable writing to the framebuffer */
+		glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
+
+		/* In order to save some fill rate we minimize the viewport using rect.
+		 * We need to get the region of the scissor so that our geometry doesn't
+		 * get rejected before the depth test. Should probably cull rect against
+		 * scissor for viewport but this is a rare case I think */
+		glGetFloatv(GL_SCISSOR_BOX, viewport);
+		if (!input || input->xmin == input->xmax) {
+			glViewport(viewport[0], viewport[1], 24, 24);
+		}
+		else {
+			glViewport(viewport[0], viewport[1], (int)(input->xmax - input->xmin), (int)(input->ymax - input->ymin));
+		}
+
+		/* occlusion queries operates on fragments that pass tests and since we are interested on all
+		 * objects in the view frustum independently of their order, we need to disable the depth test */
+		if (mode == GPU_SELECT_ALL) {
+			glDisable(GL_DEPTH_TEST);
+			glDepthMask(GL_FALSE);
+		}
+		else if (mode == GPU_SELECT_NEAREST_FIRST_PASS) {
+			glClear(GL_DEPTH_BUFFER_BIT);
+			glEnable(GL_DEPTH_TEST);
+			glDepthMask(GL_TRUE);
+			glDepthFunc(GL_LEQUAL);
+		}
+		else if (mode == GPU_SELECT_NEAREST_SECOND_PASS) {
+			glEnable(GL_DEPTH_TEST);
+			glDepthMask(GL_TRUE);
+			glDepthFunc(GL_EQUAL);
+		}
+	}
+}
+
+bool GPU_select_load_id(unsigned int id)
+{
+	/* if no selection mode active, ignore */
+	if(!g_query_state.select_is_active)
+		return true;
+
+	if (!g_query_state.use_gpu_select) {
+		glLoadName(id);
+	}
+	else {
+		if (g_query_state.query_issued) {
+			glEndQueryARB(GL_SAMPLES_PASSED_ARB);
+		}
+		/* if required, allocate extra queries */
+		if (g_query_state.active_query == g_query_state.num_of_queries) {
+			g_query_state.num_of_queries += ALLOC_QUERIES;
+			g_query_state.queries = MEM_reallocN(g_query_state.queries, g_query_state.num_of_queries * sizeof(*g_query_state.queries));
+			g_query_state.id = MEM_reallocN(g_query_state.id, g_query_state.num_of_queries * sizeof(*g_query_state.id));
+			glGenQueriesARB(ALLOC_QUERIES, &g_query_state.queries[g_query_state.active_query]);
+		}
+
+		glBeginQueryARB(GL_SAMPLES_PASSED_ARB, g_query_state.queries[g_query_state.active_query]);
+		g_query_state.id[g_query_state.active_query] = id;
+		g_query_state.active_query++;
+		g_query_state.query_issued = true;
+
+		if (g_query_state.mode == GPU_SELECT_NEAREST_SECOND_PASS) {
+			if (g_query_state.buffer[g_query_state.index * 4 + 3] == id) {
+				g_query_state.index++;
+				return true;
+			}
+			else {
+				return false;
+			}
+		}
+	}
+
+	return true;
+}
+
+unsigned int GPU_select_end(void)
+{
+	unsigned int hits = 0;
+	if (!g_query_state.use_gpu_select) {
+		glPopName();
+		hits = glRenderMode(GL_RENDER);
+	}
+	else {
+		int i;
+
+		if (g_query_state.query_issued) {
+			glEndQueryARB(GL_SAMPLES_PASSED_ARB);
+		}
+
+		for (i = 0; i < g_query_state.active_query; i++) {
+			unsigned int result;
+			glGetQueryObjectuivARB(g_query_state.queries[i], GL_QUERY_RESULT_ARB, &result);
+			if (result > 0) {
+				if (g_query_state.mode != GPU_SELECT_NEAREST_SECOND_PASS) {
+					if(hits < g_query_state.bufsize) {
+						g_query_state.buffer[hits * 4] = 1;
+						g_query_state.buffer[hits * 4 + 1] = 0xFFFF;
+						g_query_state.buffer[hits * 4 + 2] = 0xFFFF;
+						g_query_state.buffer[hits * 4 + 3] = g_query_state.id[i];
+
+						hits++;
+					}
+					else {
+						hits = -1;
+						break;
+					}
+				}
+				else {
+					int j;
+					/* search in buffer and make selected object first */
+					for (j = 0; j < g_query_state.oldhits; j++) {
+						if (g_query_state.buffer[j * 4 + 3] == g_query_state.id[i]) {
+							g_query_state.buffer[j * 4 + 1] = 0;
+							g_query_state.buffer[j * 4 + 2] = 0;
+						}
+					}
+					break;
+				}
+			}
+		}
+
+		glDeleteQueriesARB(g_query_state.num_of_queries, g_query_state.queries);
+		MEM_freeN(g_query_state.queries);
+		MEM_freeN(g_query_state.id);
+		glPopAttrib();
+		glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
+	}
+
+	g_query_state.select_is_active = false;
+
+	return hits;
+}
+
+
+bool GPU_select_query_check_support(void)
+{
+	return GLEW_ARB_occlusion_query;
+}
+
+
+bool GPU_select_query_check_active(void)
+{
+	return GLEW_ARB_occlusion_query &&
+	       ((U.gpu_select_method == USER_SELECT_USE_OCCLUSION_QUERY) ||
+	        ((U.gpu_select_method == USER_SELECT_AUTO) && GPU_type_matches(GPU_DEVICE_ATI, GPU_OS_ANY, GPU_DRIVER_ANY)));
+}