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

3 files changed, 54 insertions, 72 deletions

diff --git a/source/blender/editors/mesh/editface.c b/source/blender/editors/mesh/editface.c
index 5afde1b3ba1..e226985300c 100644
--- a/source/blender/editors/mesh/editface.c
+++ b/source/blender/editors/mesh/editface.c
@@ -272,7 +272,7 @@ void paintface_select_linked(bContext *C, Object *ob, const int mval[2], const b
 	if (me == NULL || me->totpoly == 0) return;
 
 	if (mval) {
-		if (!ED_mesh_pick_face(C, ob, mval, &index, ED_MESH_PICK_DEFAULT_FACE_SIZE)) {
+		if (!ED_mesh_pick_face(C, ob, mval, &index, ED_MESH_PICK_DEFAULT_FACE_DIST)) {
 			return;
 		}
 	}
@@ -374,7 +374,7 @@ bool paintface_mouse_select(struct bContext *C, Object *ob, const int mval[2], b
 	/* Get the face under the cursor */
 	me = BKE_mesh_from_object(ob);
 
-	if (!ED_mesh_pick_face(C, ob, mval, &index, ED_MESH_PICK_DEFAULT_FACE_SIZE))
+	if (!ED_mesh_pick_face(C, ob, mval, &index, ED_MESH_PICK_DEFAULT_FACE_DIST))
 		return false;
 
 	if (index >= me->totpoly)
@@ -418,22 +418,17 @@ bool paintface_mouse_select(struct bContext *C, Object *ob, const int mval[2], b
 	return true;
 }
 
-int do_paintface_box_select(ViewContext *vc, rcti *rect, int sel_op)
+int do_paintface_box_select(ViewContext *vc, const rcti *rect, int sel_op)
 {
 	Object *ob = vc->obact;
 	Mesh *me;
 	MPoly *mpoly;
-	struct ImBuf *ibuf;
-	unsigned int *rt;
+	uint *rt;
 	char *selar;
 	int a, index;
-	const int size[2] = {
-	    BLI_rcti_size_x(rect) + 1,
-	    BLI_rcti_size_y(rect) + 1};
 
 	me = BKE_mesh_from_object(ob);
-
-	if ((me == NULL) || (me->totpoly == 0) || (size[0] * size[1] <= 0)) {
+	if ((me == NULL) || (me->totpoly == 0) || BLI_rcti_is_empty(rect)) {
 		return OPERATOR_CANCELLED;
 	}
 
@@ -443,17 +438,12 @@ int do_paintface_box_select(ViewContext *vc, rcti *rect, int sel_op)
 		paintface_deselect_all_visible(vc->C, vc->obact, SEL_DESELECT, false);
 	}
 
-	ED_view3d_backbuf_validate(vc);
+	uint buf_len;
+	uint *buf = ED_view3d_select_id_read_rect(vc, rect, &buf_len);
 
-	ibuf = IMB_allocImBuf(size[0], size[1], 32, IB_rect);
-	rt = ibuf->rect;
-	view3d_opengl_read_pixels(vc->ar, rect->xmin, rect->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]);
+	rt = buf;
 
-	a = size[0] * size[1];
+	a = buf_len;
 	while (a--) {
 		if (*rt) {
 			index = *rt;
@@ -476,7 +466,7 @@ int do_paintface_box_select(ViewContext *vc, rcti *rect, int sel_op)
 		}
 	}
 
-	IMB_freeImBuf(ibuf);
+	MEM_freeN(buf);
 	MEM_freeN(selar);
 
 #ifdef __APPLE__
diff --git a/source/blender/editors/mesh/editmesh_select.c b/source/blender/editors/mesh/editmesh_select.c
index 80d23f37e71..991e0f94383 100644
--- a/source/blender/editors/mesh/editmesh_select.c
+++ b/source/blender/editors/mesh/editmesh_select.c
@@ -213,32 +213,29 @@ bool EDBM_backbuf_border_init(
         ViewContext *vc, short xmin,
         short ymin, short xmax, short ymax)
 {
-	struct ImBuf *buf;
-	unsigned int *dr;
-	int a;
+	uint *buf, *dr, buf_len;
 
 	if (vc->obedit == NULL || !V3D_IS_ZBUF(vc->v3d)) {
 		return false;
 	}
 
-	buf = ED_view3d_backbuf_read(vc, xmin, ymin, xmax, ymax);
+	buf = ED_view3d_select_id_read(vc, xmin, ymin, xmax, ymax, &buf_len);
 	if ((buf == NULL) || (bm_vertoffs == 0)) {
 		return false;
 	}
 
-	dr = buf->rect;
+	dr = buf;
 
 	/* build selection lookup */
 	selbuf = edbm_backbuf_alloc(bm_vertoffs + 1);
 
-	a = (xmax - xmin + 1) * (ymax - ymin + 1);
-	while (a--) {
+	while (buf_len--) {
 		if (*dr > 0 && *dr <= bm_vertoffs) {
 			BLI_BITMAP_ENABLE(selbuf, *dr);
 		}
 		dr++;
 	}
-	IMB_freeImBuf(buf);
+	MEM_freeN(buf);
 	return true;
 }
 
@@ -286,9 +283,7 @@ static void edbm_mask_lasso_px_cb(int x, int x_end, int y, void *user_data)
  */
 bool EDBM_backbuf_border_mask_init(ViewContext *vc, const int mcords[][2], short tot, short xmin, short ymin, short xmax, short ymax)
 {
-	unsigned int *dr, *dr_mask, *dr_mask_arr;
-	struct ImBuf *buf;
-	int a;
+	uint *buf, *dr, *dr_mask, *dr_mask_arr, buf_len;
 	struct LassoMaskData lasso_mask_data;
 
 	/* method in use for face selecting too */
@@ -301,14 +296,14 @@ bool EDBM_backbuf_border_mask_init(ViewContext *vc, const int mcords[][2], short
 		return false;
 	}
 
-	buf = ED_view3d_backbuf_read(vc, xmin, ymin, xmax, ymax);
+	buf = ED_view3d_select_id_read(vc, xmin, ymin, xmax, ymax, &buf_len);
 	if ((buf == NULL) || (bm_vertoffs == 0)) {
 		return false;
 	}
 
-	dr = buf->rect;
+	dr = buf;
 
-	dr_mask = dr_mask_arr = MEM_callocN(sizeof(*dr_mask) * buf->x * buf->y, __func__);
+	dr_mask = dr_mask_arr = MEM_callocN(sizeof(*dr_mask) * buf_len, __func__);
 	lasso_mask_data.px = dr_mask;
 	lasso_mask_data.width = (xmax - xmin) + 1;
 
@@ -320,14 +315,13 @@ bool EDBM_backbuf_border_mask_init(ViewContext *vc, const int mcords[][2], short
 	/* build selection lookup */
 	selbuf = edbm_backbuf_alloc(bm_vertoffs + 1);
 
-	a = (xmax - xmin + 1) * (ymax - ymin + 1);
-	while (a--) {
+	while (buf_len--) {
 		if (*dr > 0 && *dr <= bm_vertoffs && *dr_mask == true) {
 			BLI_BITMAP_ENABLE(selbuf, *dr);
 		}
 		dr++; dr_mask++;
 	}
-	IMB_freeImBuf(buf);
+	MEM_freeN(buf);
 	MEM_freeN(dr_mask_arr);
 
 	return true;
@@ -338,8 +332,7 @@ bool EDBM_backbuf_circle_init(
         ViewContext *vc,
         short xs, short ys, short rads)
 {
-	struct ImBuf *buf;
-	unsigned int *dr;
+	uint *buf, *dr;
 	short xmin, ymin, xmax, ymax, xc, yc;
 	int radsq;
 
@@ -355,12 +348,12 @@ bool EDBM_backbuf_circle_init(
 
 	xmin = xs - rads; xmax = xs + rads;
 	ymin = ys - rads; ymax = ys + rads;
-	buf = ED_view3d_backbuf_read(vc, xmin, ymin, xmax, ymax);
+	buf = ED_view3d_select_id_read(vc, xmin, ymin, xmax, ymax, NULL);
 	if ((buf == NULL) || (bm_vertoffs == 0)) {
 		return false;
 	}
 
-	dr = buf->rect;
+	dr = buf;
 
 	/* build selection lookup */
 	selbuf = edbm_backbuf_alloc(bm_vertoffs + 1);
@@ -375,7 +368,7 @@ bool EDBM_backbuf_circle_init(
 		}
 	}
 
-	IMB_freeImBuf(buf);
+	MEM_freeN(buf);
 	return true;
 
 }
@@ -472,26 +465,24 @@ BMVert *EDBM_vert_find_nearest_ex(
 	BMesh *bm = vc->em->bm;
 
 	if (V3D_IS_ZBUF(vc->v3d)) {
-		const int dist_px = ED_view3d_backbuf_sample_size_clamp(vc->ar, *r_dist);
-		float dist_test;
+		uint dist_px = (uint)ED_view3d_backbuf_sample_size_clamp(vc->ar, *r_dist);
 		unsigned int index;
 		BMVert *eve;
 
 		/* No afterqueue (yet), so we check it now, otherwise the bm_xxxofs indices are bad. */
 		{
 			FAKE_SELECT_MODE_BEGIN(vc, fake_select_mode, select_mode, SCE_SELECT_VERTEX);
-			ED_view3d_backbuf_validate_with_select_mode(vc, select_mode);
+			ED_view3d_select_id_validate_with_select_mode(vc, select_mode);
 
-			index = ED_view3d_backbuf_sample_rect(
-			            vc, vc->mval, dist_px, bm_wireoffs, 0xFFFFFF, &dist_test);
+			index = ED_view3d_select_id_read_nearest(vc, vc->mval, bm_wireoffs, 0xFFFFFF, &dist_px);
 			eve = index ? BM_vert_at_index_find_or_table(bm, index - 1) : NULL;
 
 			FAKE_SELECT_MODE_END(vc, fake_select_mode);
 		}
 
 		if (eve) {
-			if (dist_test < *r_dist) {
-				*r_dist = dist_test;
+			if (dist_px < *r_dist) {
+				*r_dist = dist_px;
 				return eve;
 			}
 		}
@@ -665,17 +656,16 @@ BMEdge *EDBM_edge_find_nearest_ex(
 	BMesh *bm = vc->em->bm;
 
 	if (V3D_IS_ZBUF(vc->v3d)) {
-		const int dist_px = ED_view3d_backbuf_sample_size_clamp(vc->ar, *r_dist);
-		float dist_test = 0.0f;
+		uint dist_px = (uint)ED_view3d_backbuf_sample_size_clamp(vc->ar, *r_dist);
 		unsigned int index;
 		BMEdge *eed;
 
 		/* No afterqueue (yet), so we check it now, otherwise the bm_xxxofs indices are bad. */
 		{
 			FAKE_SELECT_MODE_BEGIN(vc, fake_select_mode, select_mode, SCE_SELECT_EDGE);
-			ED_view3d_backbuf_validate_with_select_mode(vc, select_mode);
+			ED_view3d_select_id_validate_with_select_mode(vc, select_mode);
 
-			index = ED_view3d_backbuf_sample_rect(vc, vc->mval, dist_px, bm_solidoffs, bm_wireoffs, &dist_test);
+			index = ED_view3d_select_id_read_nearest(vc, vc->mval, bm_solidoffs, bm_wireoffs, &dist_px);
 			eed = index ? BM_edge_at_index_find_or_table(bm, index - 1) : NULL;
 
 			FAKE_SELECT_MODE_END(vc, fake_select_mode);
@@ -703,8 +693,8 @@ BMEdge *EDBM_edge_find_nearest_ex(
 		/* end exception */
 
 		if (eed) {
-			if (dist_test < *r_dist) {
-				*r_dist = dist_test;
+			if (dist_px < *r_dist) {
+				*r_dist = dist_px;
 				return eed;
 			}
 		}
@@ -842,9 +832,9 @@ BMFace *EDBM_face_find_nearest_ex(
 
 		{
 			FAKE_SELECT_MODE_BEGIN(vc, fake_select_mode, select_mode, SCE_SELECT_FACE);
-			ED_view3d_backbuf_validate_with_select_mode(vc, select_mode);
+			ED_view3d_select_id_validate_with_select_mode(vc, select_mode);
 
-			index = ED_view3d_backbuf_sample(vc, vc->mval[0], vc->mval[1]);
+			index = ED_view3d_select_id_sample(vc, vc->mval[0], vc->mval[1]);
 			efa = index ? BM_face_at_index_find_or_table(bm, index - 1) : NULL;
 
 			FAKE_SELECT_MODE_END(vc, fake_select_mode);
@@ -974,7 +964,6 @@ static bool unified_findnearest(
 			Object *obedit = base_iter->object;
 			ED_view3d_viewcontext_init_object(vc, obedit);
 			BLI_assert(vc->em->selectmode == em->selectmode);
-			ED_view3d_backbuf_validate(vc);
 			BMFace *efa_zbuf = NULL;
 			BMFace *efa_test = EDBM_face_find_nearest_ex(vc, &dist, dist_center_p, true, use_cycle, &efa_zbuf);
 			if (efa_test && dist_center_p) {
@@ -999,7 +988,6 @@ static bool unified_findnearest(
 			Base *base_iter = bases[base_index];
 			Object *obedit = base_iter->object;
 			ED_view3d_viewcontext_init_object(vc, obedit);
-			ED_view3d_backbuf_validate(vc);
 			BMEdge *eed_zbuf = NULL;
 			BMEdge *eed_test = EDBM_edge_find_nearest_ex(vc, &dist, dist_center_p, true, use_cycle, &eed_zbuf);
 			if (eed_test && dist_center_p) {
@@ -1021,7 +1009,6 @@ static bool unified_findnearest(
 			Base *base_iter = bases[base_index];
 			Object *obedit = base_iter->object;
 			ED_view3d_viewcontext_init_object(vc, obedit);
-			ED_view3d_backbuf_validate(vc);
 			BMVert *eve_test = EDBM_vert_find_nearest_ex(vc, &dist, true, use_cycle);
 			if (eve_test) {
 				hit.v.base_index = base_index;
diff --git a/source/blender/editors/mesh/meshtools.c b/source/blender/editors/mesh/meshtools.c
index 2b8535f868b..952690775b7 100644
--- a/source/blender/editors/mesh/meshtools.c
+++ b/source/blender/editors/mesh/meshtools.c
@@ -1014,7 +1014,7 @@ int *mesh_get_x_mirror_faces(Object *ob, BMEditMesh *em, Mesh *me_eval)
  *
  * \return boolean true == Found
  */
-bool ED_mesh_pick_face(bContext *C, Object *ob, const int mval[2], unsigned int *index, int size)
+bool ED_mesh_pick_face(bContext *C, Object *ob, const int mval[2], unsigned int *index, int dist_px)
 {
 	ViewContext vc;
 	Mesh *me = ob->data;
@@ -1026,16 +1026,18 @@ bool ED_mesh_pick_face(bContext *C, Object *ob, const int mval[2], unsigned int
 
 	ED_view3d_viewcontext_init(C, &vc);
 
-	if (size) {
+	if (dist_px) {
 		/* sample rect to increase chances of selecting, so that when clicking
 		 * on an edge in the backbuf, we can still select a face */
 
-		float dummy_dist;
-		*index = ED_view3d_backbuf_sample_rect(&vc, mval, size, 1, me->totpoly + 1, &dummy_dist);
+		ED_view3d_select_id_validate(&vc);
+
+		*index = ED_view3d_select_id_read_nearest(
+		        &vc, mval, 1, me->totpoly + 1, &dist_px);
 	}
 	else {
 		/* sample only on the exact position */
-		*index = ED_view3d_backbuf_sample(&vc, mval[0], mval[1]);
+		*index = ED_view3d_select_id_sample(&vc, mval[0], mval[1]);
 	}
 
 	if ((*index) == 0 || (*index) > (unsigned int)me->totpoly)
@@ -1045,6 +1047,7 @@ bool ED_mesh_pick_face(bContext *C, Object *ob, const int mval[2], unsigned int
 
 	return true;
 }
+
 static void ed_mesh_pick_face_vert__mpoly_find(
         /* context */
         struct ARegion *ar, const float mval[2],
@@ -1073,7 +1076,7 @@ static void ed_mesh_pick_face_vert__mpoly_find(
  * Use when the back buffer stores face index values. but we want a vert.
  * This gets the face then finds the closest vertex to mval.
  */
-bool ED_mesh_pick_face_vert(bContext *C, Object *ob, const int mval[2], unsigned int *index, int size)
+bool ED_mesh_pick_face_vert(bContext *C, Object *ob, const int mval[2], unsigned int *index, int dist_px)
 {
 	Depsgraph *depsgraph = CTX_data_depsgraph(C);
 	unsigned int poly_index;
@@ -1081,7 +1084,7 @@ bool ED_mesh_pick_face_vert(bContext *C, Object *ob, const int mval[2], unsigned
 
 	BLI_assert(me && GS(me->id.name) == ID_ME);
 
-	if (ED_mesh_pick_face(C, ob, mval, &poly_index, size)) {
+	if (ED_mesh_pick_face(C, ob, mval, &poly_index, dist_px)) {
 		Scene *scene_eval = DEG_get_evaluated_scene(depsgraph);
 		Object *ob_eval = DEG_get_evaluated_object(depsgraph, ob);
 		struct ARegion *ar = CTX_wm_region(C);
@@ -1181,7 +1184,7 @@ static void ed_mesh_pick_vert__mapFunc(void *userData, int index, const float co
 		}
 	}
 }
-bool ED_mesh_pick_vert(bContext *C, Object *ob, const int mval[2], unsigned int *index, int size, bool use_zbuf)
+bool ED_mesh_pick_vert(bContext *C, Object *ob, const int mval[2], unsigned int *index, int dist_px, bool use_zbuf)
 {
 	ViewContext vc;
 	Mesh *me = ob->data;
@@ -1194,16 +1197,18 @@ bool ED_mesh_pick_vert(bContext *C, Object *ob, const int mval[2], unsigned int
 	ED_view3d_viewcontext_init(C, &vc);
 
 	if (use_zbuf) {
-		if (size > 0) {
+		if (dist_px > 0) {
 			/* sample rect to increase chances of selecting, so that when clicking
 			 * on an face in the backbuf, we can still select a vert */
 
-			float dummy_dist;
-			*index = ED_view3d_backbuf_sample_rect(&vc, mval, size, 1, me->totvert + 1, &dummy_dist);
+			ED_view3d_select_id_validate(&vc);
+
+			*index = ED_view3d_select_id_read_nearest(
+			        &vc, mval, 1, me->totvert + 1, &dist_px);
 		}
 		else {
 			/* sample only on the exact position */
-			*index = ED_view3d_backbuf_sample(&vc, mval[0], mval[1]);
+			*index = ED_view3d_select_id_sample(&vc, mval[0], mval[1]);
 		}
 
 		if ((*index) == 0 || (*index) > (unsigned int)me->totvert)