GPU: Simplify select shaders.

The shaders are: `GPU_SHADER_3D_FLAT_SELECT_ID` and `GPU_SHADER_3D_UNIFORM_SELECT_ID`.
This commit allows the drawing of the mesh select ids to be done on a 32UI format texture.
This simplifies the shader that previously acted on the backbuffer and had to do an uint to rgba conversion.

Differential Revision: https://developer.blender.org/D4350

5 files changed, 173 insertions, 177 deletions

diff --git a/source/blender/editors/space_view3d/drawobject.c b/source/blender/editors/space_view3d/drawobject.c
index e6e0438164c..b976c231841 100644
--- a/source/blender/editors/space_view3d/drawobject.c
+++ b/source/blender/editors/space_view3d/drawobject.c
@@ -47,6 +47,8 @@
 
 #include "UI_resources.h"
 
+#include "DRW_engine.h"
+
 #include "view3d_intern.h"  /* bad level include */
 
 #include "../../draw/intern/draw_cache_impl.h"  /* bad level include (temporary) */
@@ -281,7 +283,7 @@ static void bbs_mesh_solid_faces(Scene *UNUSED(scene), Object *ob, const float w
 	bbs_mesh_face(geom_faces, true, world_clip_planes);
 }
 
-void draw_object_backbufsel(
+void draw_object_select_id(
         Depsgraph *depsgraph, Scene *scene, View3D *v3d, RegionView3D *rv3d, Object *ob,
         short select_mode)
 {
@@ -380,6 +382,52 @@ void draw_object_backbufsel(
 	GPU_matrix_set(rv3d->viewmat);
 }
 
+void draw_object_depth(RegionView3D *rv3d, Object *ob)
+{
+	GPU_matrix_mul(ob->obmat);
+	GPU_depth_test(true);
+
+	const float (*world_clip_planes)[4] = NULL;
+	if (rv3d->rflag & RV3D_CLIPPING) {
+		ED_view3d_clipping_local(rv3d, ob->obmat);
+		world_clip_planes = rv3d->clip_local;
+	}
+
+	switch (ob->type) {
+		case OB_MESH:
+			{
+				GPUBatch *batch;
+
+				Mesh *me = ob->data;
+
+				if (ob->mode & OB_MODE_EDIT) {
+					batch = DRW_mesh_batch_cache_get_edit_triangles(me);
+				}
+				else {
+					batch = DRW_mesh_batch_cache_get_surface(me);
+				}
+
+				DRW_mesh_batch_cache_create_requested(ob, me, NULL, false, true);
+
+				DRW_opengl_context_enable();
+				const eGPUShaderConfig sh_cfg = world_clip_planes ? GPU_SHADER_CFG_CLIPPED : GPU_SHADER_CFG_DEFAULT;
+				GPU_batch_program_set_builtin_with_config(batch, GPU_SHADER_3D_DEPTH_ONLY, sh_cfg);
+				if (world_clip_planes != NULL) {
+					bbs_world_clip_planes_from_rv3d(batch, world_clip_planes);
+				}
+
+				GPU_batch_draw(batch);
+				DRW_opengl_context_disable();
+			}
+			break;
+		case OB_CURVE:
+		case OB_SURF:
+			break;
+	}
+
+	GPU_matrix_set(rv3d->viewmat);
+}
+
 
 void ED_draw_object_facemap(
         Depsgraph *depsgraph, Object *ob, const float col[4], const int facemap)
diff --git a/source/blender/editors/space_view3d/space_view3d.c b/source/blender/editors/space_view3d/space_view3d.c
index ca18a96c253..25cc8854607 100644
--- a/source/blender/editors/space_view3d/space_view3d.c
+++ b/source/blender/editors/space_view3d/space_view3d.c
@@ -536,11 +536,6 @@ static void view3d_main_region_exit(wmWindowManager *wm, ARegion *ar)
 	RegionView3D *rv3d = ar->regiondata;
 
 	ED_view3d_stop_render_preview(wm, ar);
-
-	if (rv3d->gpuoffscreen) {
-		GPU_offscreen_free(rv3d->gpuoffscreen);
-		rv3d->gpuoffscreen = NULL;
-	}
 }
 
 static bool view3d_ob_drop_poll(bContext *UNUSED(C), wmDrag *drag, const wmEvent *UNUSED(event), const char **UNUSED(tooltip))
@@ -729,9 +724,6 @@ static void view3d_main_region_free(ARegion *ar)
 		if (rv3d->sms) {
 			MEM_freeN(rv3d->sms);
 		}
-		if (rv3d->gpuoffscreen) {
-			GPU_offscreen_free(rv3d->gpuoffscreen);
-		}
 
 		MEM_freeN(rv3d);
 		ar->regiondata = NULL;
@@ -751,7 +743,6 @@ static void *view3d_main_region_duplicate(void *poin)
 			new->clipbb = MEM_dupallocN(rv3d->clipbb);
 
 		new->depths = NULL;
-		new->gpuoffscreen = NULL;
 		new->render_engine = NULL;
 		new->sms = NULL;
 		new->smooth_timer = NULL;
diff --git a/source/blender/editors/space_view3d/view3d_draw_legacy.c b/source/blender/editors/space_view3d/view3d_draw_legacy.c
index a52fd89d284..eed6fc31235 100644
--- a/source/blender/editors/space_view3d/view3d_draw_legacy.c
+++ b/source/blender/editors/space_view3d/view3d_draw_legacy.c
@@ -149,7 +149,7 @@ void ED_view3d_clipping_enable(void)
 
 /* *********************** backdraw for selection *************** */
 
-static void backdrawview3d(
+static void validate_object_select_id(
         struct Depsgraph *depsgraph, Scene *scene,
         ARegion *ar, View3D *v3d,
         Object *obact, Object *obedit,
@@ -203,81 +203,24 @@ static void backdrawview3d(
 	if (v3d->shading.type > OB_WIRE) v3d->zbuf = true;
 #endif
 
-	/* dithering and AA break color coding, so disable */
-	glDisable(GL_DITHER);
-
-	if (false) {
-		/* for multisample we use an offscreen FBO. multisample drawing can fail
-		 * with color coded selection drawing, and reading back depths from such
-		 * a buffer can also cause a few seconds freeze on OS X / NVidia.
-		 *
-		 * NOTE: code is no longer used now, but offscreen drawing is likely
-		 * what we will always want to do for the new viewport. */
-		int w = BLI_rcti_size_x(&ar->winrct);
-		int h = BLI_rcti_size_y(&ar->winrct);
-		char error[256];
-
-		if (rv3d->gpuoffscreen) {
-			if (GPU_offscreen_width(rv3d->gpuoffscreen)  != w ||
-			    GPU_offscreen_height(rv3d->gpuoffscreen) != h)
-			{
-				GPU_offscreen_free(rv3d->gpuoffscreen);
-				rv3d->gpuoffscreen = NULL;
-			}
-		}
-
-		if (!rv3d->gpuoffscreen) {
-			rv3d->gpuoffscreen = GPU_offscreen_create(w, h, 0, true, false, error);
-
-			if (!rv3d->gpuoffscreen)
-				fprintf(stderr, "Failed to create offscreen selection buffer for multisample: %s\n", error);
-		}
-	}
-
-	if (rv3d->gpuoffscreen)
-		GPU_offscreen_bind(rv3d->gpuoffscreen, true);
-	else
-		GPU_scissor(ar->winrct.xmin, ar->winrct.ymin, BLI_rcti_size_x(&ar->winrct), BLI_rcti_size_y(&ar->winrct));
-
-	GPU_clear_color(0.0, 0.0, 0.0, 0.0);
-	GPU_depth_test(true);
-	GPU_clear(GPU_COLOR_BIT | GPU_DEPTH_BIT);
-
-	if (rv3d->rflag & RV3D_CLIPPING)
-		ED_view3d_clipping_set(rv3d);
-
 	G.f |= G_FLAG_BACKBUFSEL;
 
 	if (obact_eval && ((obact_eval->base_flag & BASE_VISIBLE) != 0)) {
-		draw_object_backbufsel(depsgraph, scene_eval, v3d, rv3d, obact_eval, select_mode);
+		DRW_framebuffer_select_id_setup(ar, true);
+		draw_object_select_id(depsgraph, scene_eval, v3d, rv3d, obact_eval, select_mode);
+		DRW_framebuffer_select_id_release(ar);
 	}
 
-	if (rv3d->gpuoffscreen)
-		GPU_offscreen_unbind(rv3d->gpuoffscreen, true);
-
+	/* TODO: Create a flag in `DRW_manager` because the drawing is no longer
+	 *       made on the backbuffer in this case. */
 	v3d->flag &= ~V3D_INVALID_BACKBUF;
 
 	G.f &= ~G_FLAG_BACKBUFSEL;
-	GPU_depth_test(false);
-	glEnable(GL_DITHER);
-
-	if (rv3d->rflag & RV3D_CLIPPING)
-		ED_view3d_clipping_disable();
 }
 
 void view3d_opengl_read_pixels(ARegion *ar, int x, int y, int w, int h, int format, int type, void *data)
 {
-	RegionView3D *rv3d = ar->regiondata;
-
-	if (rv3d->gpuoffscreen) {
-		GPU_offscreen_bind(rv3d->gpuoffscreen, true);
-		glReadBuffer(GL_COLOR_ATTACHMENT0);
-		glReadPixels(x, y, w, h, format, type, data);
-		GPU_offscreen_unbind(rv3d->gpuoffscreen, true);
-	}
-	else {
-		glReadPixels(ar->winrct.xmin + x, ar->winrct.ymin + y, w, h, format, type, data);
-	}
+	glReadPixels(ar->winrct.xmin + x, ar->winrct.ymin + y, w, h, format, type, data);
 }
 
 /* XXX depth reading exception, for code not using gpu offscreen */
@@ -286,16 +229,70 @@ static void view3d_opengl_read_Z_pixels(ARegion *ar, int x, int y, int w, int h,
 	glReadPixels(ar->winrct.xmin + x, ar->winrct.ymin + y, w, h, format, type, data);
 }
 
-void ED_view3d_backbuf_validate_with_select_mode(ViewContext *vc, short select_mode)
+void ED_view3d_select_id_validate_with_select_mode(ViewContext *vc, short select_mode)
 {
+	/* TODO: Create a flag in `DRW_manager` because the drawing is no longer
+	 *       made on the backbuffer in this case. */
 	if (vc->v3d->flag & V3D_INVALID_BACKBUF) {
-		backdrawview3d(vc->depsgraph, vc->scene, vc->ar, vc->v3d, vc->obact, vc->obedit, select_mode);
+		validate_object_select_id(
+		        vc->depsgraph, vc->scene, vc->ar, vc->v3d,
+		        vc->obact, vc->obedit, select_mode);
+	}
+}
+
+void ED_view3d_select_id_validate(ViewContext *vc)
+{
+	ED_view3d_select_id_validate_with_select_mode(vc, -1);
+}
+
+void ED_view3d_backbuf_depth_validate(ViewContext *vc)
+{
+	if (vc->v3d->flag & V3D_INVALID_BACKBUF) {
+		ARegion *ar = vc->ar;
+		RegionView3D *rv3d = ar->regiondata;
+		Object *obact_eval = DEG_get_evaluated_object(vc->depsgraph, vc->obact);
+
+		if (obact_eval && ((obact_eval->base_flag & BASE_VISIBLE) != 0)) {
+			GPU_scissor(ar->winrct.xmin, ar->winrct.ymin,
+			            BLI_rcti_size_x(&ar->winrct),
+			            BLI_rcti_size_y(&ar->winrct));
+
+			GPU_depth_test(true);
+			GPU_clear(GPU_DEPTH_BIT);
+
+			if (rv3d->rflag & RV3D_CLIPPING) {
+				ED_view3d_clipping_set(rv3d);
+			}
+
+			draw_object_depth(rv3d, obact_eval);
+
+			if (rv3d->rflag & RV3D_CLIPPING) {
+				ED_view3d_clipping_disable(rv3d);
+			}
+
+			GPU_depth_test(false);
+		}
+
+		vc->v3d->flag &= ~V3D_INVALID_BACKBUF;
 	}
 }
 
-void ED_view3d_backbuf_validate(ViewContext *vc)
+uint *ED_view3d_select_id_read_rect(ViewContext *vc, const rcti *clip, uint *r_buf_len)
 {
-	ED_view3d_backbuf_validate_with_select_mode(vc, -1);
+	ED_view3d_select_id_validate(vc);
+
+	uint width = BLI_rcti_size_x(clip);
+	uint height = BLI_rcti_size_y(clip);
+	uint buf_len = width * height;
+	uint *buf = MEM_mallocN(buf_len * sizeof(*buf), __func__);
+
+	DRW_framebuffer_select_id_read(clip, buf);
+
+	if (r_buf_len) {
+		*r_buf_len = buf_len;
+	}
+
+	return buf;
 }
 
 /**
@@ -308,111 +305,81 @@ int ED_view3d_backbuf_sample_size_clamp(ARegion *ar, const float dist)
 }
 
 /* samples a single pixel (copied from vpaint) */
-uint ED_view3d_backbuf_sample(
+uint ED_view3d_select_id_sample(
         ViewContext *vc, int x, int y)
 {
 	if (x >= vc->ar->winx || y >= vc->ar->winy) {
 		return 0;
 	}
 
-	ED_view3d_backbuf_validate(vc);
-
-	uint col;
-	view3d_opengl_read_pixels(vc->ar, x, y, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, &col);
-	glReadBuffer(GL_BACK);
+	uint buf_len;
+	uint *buf = ED_view3d_select_id_read(vc, x, y, x, y, &buf_len);
+	BLI_assert(0 != buf_len);
+	uint ret = buf[0];
+	MEM_freeN(buf);
 
-	if (ENDIAN_ORDER == B_ENDIAN) {
-		BLI_endian_switch_uint32(&col);
-	}
-
-	return GPU_select_to_index(col);
+	return ret;
 }
 
 /* reads full rect, converts indices */
-ImBuf *ED_view3d_backbuf_read(
-        ViewContext *vc, int xmin, int ymin, int xmax, int ymax)
+uint *ED_view3d_select_id_read(
+        ViewContext *vc, int xmin, int ymin, int xmax, int ymax, uint *r_buf_len)
 {
-	/* clip */
-	const rcti clip = {
-	    max_ii(xmin, 0), min_ii(xmax, vc->ar->winx - 1),
-	    max_ii(ymin, 0), min_ii(ymax, vc->ar->winy - 1)};
-	const int size_clip[2] = {
-	    BLI_rcti_size_x(&clip) + 1,
-	    BLI_rcti_size_y(&clip) + 1};
-
-	if (UNLIKELY((clip.xmin > clip.xmax) ||
-	             (clip.ymin > clip.ymax)))
-	{
+	if (UNLIKELY((xmin > xmax) || (ymin > ymax))) {
 		return NULL;
 	}
 
-	ImBuf *ibuf_clip = IMB_allocImBuf(size_clip[0], size_clip[1], 32, IB_rect);
-
-	ED_view3d_backbuf_validate(vc);
-
-	view3d_opengl_read_pixels(vc->ar, clip.xmin, clip.ymin, size_clip[0], size_clip[1], GL_RGBA, GL_UNSIGNED_BYTE, ibuf_clip->rect);
+	const rcti rect = {
+		.xmin = xmin, .xmax = xmax + 1,
+		.ymin = ymin, .ymax = ymax + 1,
+	};
 
-	glReadBuffer(GL_BACK);
+	uint buf_len;
+	uint *buf = ED_view3d_select_id_read_rect(vc, &rect, &buf_len);
 
-	if (ENDIAN_ORDER == B_ENDIAN) {
-		IMB_convert_rgba_to_abgr(ibuf_clip);
+	if (r_buf_len) {
+		*r_buf_len = buf_len;
 	}
 
-	GPU_select_to_index_array(ibuf_clip->rect, size_clip[0] * size_clip[1]);
-
-	if ((clip.xmin == xmin) &&
-	    (clip.xmax == xmax) &&
-	    (clip.ymin == ymin) &&
-	    (clip.ymax == ymax))
-	{
-		return ibuf_clip;
-	}
-	else {
-		/* put clipped result into a non-clipped buffer */
-		const int size[2] = {
-		    (xmax - xmin + 1),
-		    (ymax - ymin + 1)};
-
-		ImBuf *ibuf_full = IMB_allocImBuf(size[0], size[1], 32, IB_rect);
-
-		IMB_rectcpy(
-		        ibuf_full, ibuf_clip,
-		        clip.xmin - xmin, clip.ymin - ymin,
-		        0, 0,
-		        size_clip[0], size_clip[1]);
-		IMB_freeImBuf(ibuf_clip);
-		return ibuf_full;
-	}
+	return buf;
 }
 
 /* smart function to sample a rect spiralling outside, nice for backbuf selection */
-uint ED_view3d_backbuf_sample_rect(
-        ViewContext *vc, const int mval[2], int size,
-        uint min, uint max, float *r_dist)
+uint ED_view3d_select_id_read_nearest(
+        struct ViewContext *vc, const int mval[2],
+        const uint min, const uint max, uint *r_dist)
 {
+	uint index = 0;
+
 	int dirvec[4][2];
 
-	const int amount = (size - 1) / 2;
+	rcti rect;
+	BLI_rcti_init_pt_radius(&rect, mval, *r_dist);
+	rect.xmax += 1;
+	rect.ymax += 1;
+
+	uint width, height;
+	width = height = BLI_rcti_size_x(&rect);
+
+	uint buf_len = width * height;
+	uint *buf = MEM_mallocN(buf_len * sizeof(*buf), __func__);
+
+	DRW_framebuffer_select_id_read(&rect, buf);
 
-	const int minx = mval[0] - (amount + 1);
-	const int miny = mval[1] - (amount + 1);
-	ImBuf *buf = ED_view3d_backbuf_read(vc, minx, miny, minx + size - 1, miny + size - 1);
-	if (!buf) return 0;
+	BLI_assert(width == height); /* This algorithm doesn't work well with rectangles */
 
-	unsigned index = 0;
 	int rc = 0;
 
 	dirvec[0][0] = 1; dirvec[0][1] = 0;
-	dirvec[1][0] = 0; dirvec[1][1] = -size;
+	dirvec[1][0] = 0; dirvec[1][1] = -height;
 	dirvec[2][0] = -1; dirvec[2][1] = 0;
-	dirvec[3][0] = 0; dirvec[3][1] = size;
+	dirvec[3][0] = 0; dirvec[3][1] = height;
 
-	const unsigned *bufmin = buf->rect;
-	const unsigned *tbuf = buf->rect;
-	const unsigned *bufmax = buf->rect + size * size;
-	tbuf += amount * size + amount;
+	const uint *bufmin = buf;
+	const uint *bufmax = buf + buf_len;
+	const uint *tbuf = buf + (height * (int)(width / 2) + height / 2 - 1);
 
-	for (int nr = 1; nr <= size; nr++) {
+	for (int nr = 1; nr <= height; nr++) {
 		for (int a = 0; a < 2; a++) {
 			for (int b = 0; b < nr; b++) {
 				if (*tbuf && *tbuf >= min && *tbuf < max) {
@@ -421,8 +388,8 @@ uint ED_view3d_backbuf_sample_rect(
 					/* get x,y pixel coords from the offset
 					 * (manhatten distance in keeping with other screen-based selection) */
 					*r_dist = (float)(
-					        abs(((int)(tbuf - buf->rect) % size) - (size / 2)) +
-					        abs(((int)(tbuf - buf->rect) / size) - (size / 2)));
+					        abs(((int)(tbuf - buf) % height) - (height / 2)) +
+					        abs(((int)(tbuf - buf) / height) - (height / 2)));
 
 					/* indices start at 1 here */
 					index = (*tbuf - min) + 1;
@@ -441,7 +408,7 @@ uint ED_view3d_backbuf_sample_rect(
 	}
 
 exit:
-	IMB_freeImBuf(buf);
+	MEM_freeN(buf);
 	return index;
 }
 
diff --git a/source/blender/editors/space_view3d/view3d_intern.h b/source/blender/editors/space_view3d/view3d_intern.h
index bb6b96b96d5..e85558765b6 100644
--- a/source/blender/editors/space_view3d/view3d_intern.h
+++ b/source/blender/editors/space_view3d/view3d_intern.h
@@ -123,11 +123,13 @@ void VIEW3D_OT_fly(struct wmOperatorType *ot);
 void VIEW3D_OT_walk(struct wmOperatorType *ot);
 
 /* drawobject.c */
-void draw_object_backbufsel(
+void draw_object_select_id(
         struct Depsgraph *depsgraph, Scene *scene,
         View3D *v3d, RegionView3D *rv3d, struct Object *ob,
         short select_mode);
 
+void draw_object_depth(RegionView3D *rv3d, struct Object *ob);
+
 int view3d_effective_drawtype(const struct View3D *v3d);
 
 /* view3d_draw.c */
diff --git a/source/blender/editors/space_view3d/view3d_select.c b/source/blender/editors/space_view3d/view3d_select.c
index fc13968def7..02d469bfa73 100644
--- a/source/blender/editors/space_view3d/view3d_select.c
+++ b/source/blender/editors/space_view3d/view3d_select.c
@@ -1924,7 +1924,7 @@ static bool ed_wpaint_vertex_select_pick(
 	uint index = 0;
 	MVert *mv;
 
-	if (ED_mesh_pick_vert(C, obact, mval, &index, ED_MESH_PICK_DEFAULT_VERT_SIZE, use_zbuf)) {
+	if (ED_mesh_pick_vert(C, obact, mval, &index, ED_MESH_PICK_DEFAULT_VERT_DIST, use_zbuf)) {
 		mv = &me->mvert[index];
 		if (extend) {
 			mv->flag |= SELECT;
@@ -2112,22 +2112,17 @@ static void do_paintvert_box_select__doSelectVert(void *userData, MVert *mv, con
 	}
 }
 static int do_paintvert_box_select(
-        ViewContext *vc, rcti *rect, const eSelectOp sel_op)
+        ViewContext *vc, const rcti *rect, const eSelectOp sel_op)
 {
 	const bool use_zbuf = V3D_IS_ZBUF(vc->v3d);
 	Mesh *me;
 	MVert *mvert;
-	struct ImBuf *ibuf;
-	uint *rt;
+	unsigned int *rt;
 	int a, index;
 	char *selar;
-	const int size[2] = {
-	    BLI_rcti_size_x(rect) + 1,
-	    BLI_rcti_size_y(rect) + 1};
 
 	me = vc->obact->data;
-
-	if ((me == NULL) || (me->totvert == 0) || (size[0] * size[1] <= 0)) {
+	if ((me == NULL) || (me->totvert == 0) || BLI_rcti_is_empty(rect)) {
 		return OPERATOR_CANCELLED;
 	}
 
@@ -2137,20 +2132,13 @@ static int do_paintvert_box_select(
 
 	if (use_zbuf) {
 		selar = MEM_callocN(me->totvert + 1, "selar");
-		ED_view3d_backbuf_validate(vc);
 
-		ibuf = IMB_allocImBuf(size[0], size[1], 32, IB_rect);
-		rt = ibuf->rect;
-		glReadPixels(
-		        rect->xmin + vc->ar->winrct.xmin,
-		        rect->ymin + vc->ar->winrct.ymin,
-		        size[0], size[1], GL_RGBA, GL_UNSIGNED_BYTE,  ibuf->rect);
-		if (ENDIAN_ORDER == B_ENDIAN) {
-			IMB_convert_rgba_to_abgr(ibuf);
-		}
-		GPU_select_to_index_array(ibuf->rect, size[0] * size[1]);
+		uint buf_len;
+		uint *buf = ED_view3d_select_id_read_rect(vc, rect, &buf_len);
+
+		rt = buf;
 
-		a = size[0] * size[1];
+		a = buf_len;
 		while (a--) {
 			if (*rt) {
 				index = *rt;
@@ -2173,7 +2161,7 @@ static int do_paintvert_box_select(
 			}
 		}
 
-		IMB_freeImBuf(ibuf);
+		MEM_freeN(buf);
 		MEM_freeN(selar);
 
 #ifdef __APPLE__