DRW: Fix/refactor UBO & Texture binding.

Previous approach was not clear enough and caused problems.
UBOs were taking slots and not release them after a shading group even
if this UBO was only for this Shading Group (notably the nodetree ubo,
since we now share the same GPUShader for identical trees).

So I choose to have a better defined approach:
- Standard texture and ubo calls are assured to be valid for the shgrp
they are called from.
- (new) Persistent texture and ubo calls are assured to be valid accross
shgrps unless the shader changes.

The standards calls are still valids for the next shgrp but are not assured
to be so if this new shgrp binds a new texture.

This enables some optimisations by not adding redundant texture and ubo
binds.

1 files changed, 70 insertions, 34 deletions

diff --git a/source/blender/draw/intern/draw_manager_exec.c b/source/blender/draw/intern/draw_manager_exec.c
index 19b55190e6c..cf9521fece4 100644
--- a/source/blender/draw/intern/draw_manager_exec.c
+++ b/source/blender/draw/intern/draw_manager_exec.c
@@ -704,63 +704,87 @@ static void draw_geometry_execute(DRWShadingGroup *shgroup, Gwn_Batch *geom)
 	draw_geometry_execute_ex(shgroup, geom, 0, 0, false);
 }
 
-static void bind_texture(GPUTexture *tex)
+enum {
+	BIND_NONE = 0,
+	BIND_TEMP = 1,         /* Release slot after this shading group. */
+	BIND_PERSIST = 2,      /* Release slot only after the next shader change. */
+};
+
+static void bind_texture(GPUTexture *tex, char bind_type)
 {
+	int index;
+	char *slot_flags = DST.RST.bound_tex_slots;
 	int bind_num = GPU_texture_bound_number(tex);
 	if (bind_num == -1) {
 		for (int i = 0; i < GPU_max_textures(); ++i) {
-			DST.RST.bind_tex_inc = (DST.RST.bind_tex_inc + 1) % GPU_max_textures();
-			if (DST.RST.bound_tex_slots[DST.RST.bind_tex_inc] == false) {
-				if (DST.RST.bound_texs[DST.RST.bind_tex_inc] != NULL) {
-					GPU_texture_unbind(DST.RST.bound_texs[DST.RST.bind_tex_inc]);
+			index = DST.RST.bind_tex_inc = (DST.RST.bind_tex_inc + 1) % GPU_max_textures();
+			if (slot_flags[index] == BIND_NONE) {
+				if (DST.RST.bound_texs[index] != NULL) {
+					GPU_texture_unbind(DST.RST.bound_texs[index]);
 				}
-				GPU_texture_bind(tex, DST.RST.bind_tex_inc);
-				DST.RST.bound_texs[DST.RST.bind_tex_inc] = tex;
-				DST.RST.bound_tex_slots[DST.RST.bind_tex_inc] = true;
+				GPU_texture_bind(tex, index);
+				DST.RST.bound_texs[index] = tex;
+				slot_flags[index] = bind_type;
 				// printf("Binds Texture %d %p\n", DST.RST.bind_tex_inc, tex);
 				return;
 			}
 		}
-
 		printf("Not enough texture slots! Reduce number of textures used by your shader.\n");
 	}
-	DST.RST.bound_tex_slots[bind_num] = true;
+	slot_flags[bind_num] = bind_type;
 }
 
-static void bind_ubo(GPUUniformBuffer *ubo)
+static void bind_ubo(GPUUniformBuffer *ubo, char bind_type)
 {
+	int index;
+	char *slot_flags = DST.RST.bound_ubo_slots;
 	int bind_num = GPU_uniformbuffer_bindpoint(ubo);
 	if (bind_num == -1) {
 		for (int i = 0; i < GPU_max_ubo_binds(); ++i) {
-			DST.RST.bind_ubo_inc = (DST.RST.bind_ubo_inc + 1) % GPU_max_ubo_binds();
-			if (DST.RST.bound_ubo_slots[DST.RST.bind_ubo_inc] == false) {
-				if (DST.RST.bound_ubos[DST.RST.bind_ubo_inc] != NULL) {
-					GPU_uniformbuffer_unbind(DST.RST.bound_ubos[DST.RST.bind_ubo_inc]);
+			index = DST.RST.bind_ubo_inc = (DST.RST.bind_ubo_inc + 1) % GPU_max_ubo_binds();
+			if (slot_flags[index] == BIND_NONE) {
+				if (DST.RST.bound_ubos[index] != NULL) {
+					GPU_uniformbuffer_unbind(DST.RST.bound_ubos[index]);
 				}
-				GPU_uniformbuffer_bind(ubo, DST.RST.bind_ubo_inc);
-				DST.RST.bound_ubos[DST.RST.bind_ubo_inc] = ubo;
-				DST.RST.bound_ubo_slots[DST.RST.bind_ubo_inc] = true;
+				GPU_uniformbuffer_bind(ubo, index);
+				DST.RST.bound_ubos[index] = ubo;
+				slot_flags[bind_num] = bind_type;
 				return;
 			}
 		}
-		/* This is not depending on user input.
-		 * It is our responsability to make sure there enough slots. */
-		BLI_assert(0 && "Not enough ubo slots! This should not happen!\n");
-
 		/* printf so user can report bad behaviour */
 		printf("Not enough ubo slots! This should not happen!\n");
+		/* This is not depending on user input.
+		 * It is our responsability to make sure there is enough slots. */
+		BLI_assert(0);
 	}
-	DST.RST.bound_ubo_slots[bind_num] = true;
+	slot_flags[bind_num] = bind_type;
 }
 
-static void release_texture_slots(void)
+static void release_texture_slots(bool with_persist)
 {
-	memset(DST.RST.bound_tex_slots, 0x0, sizeof(bool) * GPU_max_textures());
+	if (with_persist) {
+		memset(DST.RST.bound_tex_slots, 0x0, sizeof(*DST.RST.bound_tex_slots) * GPU_max_ubo_binds());
+	}
+	else {
+		for (int i = 0; i < GPU_max_ubo_binds(); ++i) {
+			if (DST.RST.bound_tex_slots[i] != BIND_PERSIST)
+				DST.RST.bound_tex_slots[i] = BIND_NONE;
+		}
+	}
 }
 
-static void release_ubo_slots(void)
+static void release_ubo_slots(bool with_persist)
 {
-	memset(DST.RST.bound_ubo_slots, 0x0, sizeof(bool) * GPU_max_textures());
+	if (with_persist) {
+		memset(DST.RST.bound_ubo_slots, 0x0, sizeof(*DST.RST.bound_ubo_slots) * GPU_max_ubo_binds());
+	}
+	else {
+		for (int i = 0; i < GPU_max_ubo_binds(); ++i) {
+			if (DST.RST.bound_ubo_slots[i] != BIND_PERSIST)
+				DST.RST.bound_ubo_slots[i] = BIND_NONE;
+		}
+	}
 }
 
 static void draw_shgroup(DRWShadingGroup *shgroup, DRWState pass_state)
@@ -771,16 +795,17 @@ static void draw_shgroup(DRWShadingGroup *shgroup, DRWState pass_state)
 	GPUUniformBuffer *ubo;
 	int val;
 	float fval;
+	const bool shader_changed = (DST.shader != shgroup->shader);
 
-	if (DST.shader != shgroup->shader) {
+	if (shader_changed) {
 		if (DST.shader) GPU_shader_unbind();
 		GPU_shader_bind(shgroup->shader);
 		DST.shader = shgroup->shader;
-
-		release_texture_slots();
-		release_ubo_slots();
 	}
 
+	release_ubo_slots(shader_changed);
+	release_texture_slots(shader_changed);
+
 	drw_state_set((pass_state & shgroup->state_extra_disable) | shgroup->state_extra);
 	drw_stencil_set(shgroup->stencil_mask);
 
@@ -810,7 +835,13 @@ static void draw_shgroup(DRWShadingGroup *shgroup, DRWState pass_state)
 			case DRW_UNIFORM_TEXTURE:
 				tex = (GPUTexture *)uni->value;
 				BLI_assert(tex);
-				bind_texture(tex);
+				bind_texture(tex, BIND_TEMP);
+				GPU_shader_uniform_texture(shgroup->shader, uni->location, tex);
+				break;
+			case DRW_UNIFORM_TEXTURE_PERSIST:
+				tex = (GPUTexture *)uni->value;
+				BLI_assert(tex);
+				bind_texture(tex, BIND_PERSIST);
 				GPU_shader_uniform_texture(shgroup->shader, uni->location, tex);
 				break;
 			case DRW_UNIFORM_BUFFER:
@@ -819,12 +850,17 @@ static void draw_shgroup(DRWShadingGroup *shgroup, DRWState pass_state)
 				}
 				tex = *((GPUTexture **)uni->value);
 				BLI_assert(tex);
-				bind_texture(tex);
+				bind_texture(tex, BIND_TEMP);
 				GPU_shader_uniform_texture(shgroup->shader, uni->location, tex);
 				break;
 			case DRW_UNIFORM_BLOCK:
 				ubo = (GPUUniformBuffer *)uni->value;
-				bind_ubo(ubo);
+				bind_ubo(ubo, BIND_TEMP);
+				GPU_shader_uniform_buffer(shgroup->shader, uni->location, ubo);
+				break;
+			case DRW_UNIFORM_BLOCK_PERSIST:
+				ubo = (GPUUniformBuffer *)uni->value;
+				bind_ubo(ubo, BIND_PERSIST);
 				GPU_shader_uniform_buffer(shgroup->shader, uni->location, ubo);
 				break;
 		}