GLES2 2D batching - item reordering, light joining and light modulate fix

Although 2D draws in painters order with strict ordering, in certain circumstances items can be reordered to increase batching / decrease state changes, without affecting the end result. This can be determined by an overlap test.

In situation with item:
A-B-A
providing the third item does not overlap the second, they can be reordered:
A-A-B

Items already contain an AABB which can be used for this overlap test.

1)
To utilise this, I have implemented item reordering (only for single rects for now), with the lookahead adjustable in project settings. This can increase performance in situations where items may not be grouped in the scene tree by texture. It can also be switched off (by setting lookahead to 0).

2)
This same trick can be used to help join items that are lit. Lit items previously would prevent joining completely, thus missing out on performance gains other than multi-command items such as tilemaps.

In this PR, lights are assigned as bits in a bitfield (up to 64, the optimization is disabled above this), and on each try_item (for joining), the bitfield for lights and shadows is constructed and compared with the previous items. If these match the 2 items can potentially be joined. However, this can only be done without changing the rendered result if an overlap test is successful.

This overlap test can be adjusted to join items up to a specific number of item references, selectable in project settings, or turned off.

3)
The legacy uniform single rect drawing routine seems to have been identified as the source of flicker, particularly on nvidia. However, it can also be up to 2x as fast. Because of the speed the batching contains a fallback where it can use the legacy single rect method, but I have now added a project setting to make this switchable. In most cases with batching it should not be necessary (as single rects are drawn less frequently) and thus the flickering can be totally avoided.

4)
This PR also fixes a color modulate bug when drawing light passes, in certain situations (particularly custom _draw routines with multiple rects).

5)
This PR also fixes #38291, a bug in the legacy renderer where light passes could draw rects in wrong position.

doc/classes/ProjectSettings.xml

@@ -975,12 +975,21 @@
 		<member name="rendering/gles2/batching/colored_vertex_format_threshold" type="float" setter="" getter="" default="0.25">
 			Including color in the vertex format has a cost, however, not including color prevents batching across color changes. This threshold determines the ratio of [code]number of vertex color changes / total number of vertices[/code] above which vertices will be translated to colored format. A value of 0 will always use colored vertices, 1 will never use colored vertices.
 		</member>
+		<member name="rendering/gles2/batching/item_reordering_lookahead" type="int" setter="" getter="" default="4">
+			In certain circumstances, the batcher can reorder items in order to better join them. This may result in better performance. An overlap test is needed however for each item lookahead, so there is a trade off, with diminishing returns. If you are getting no benefit, setting this to 0 will switch it off.
+		</member>
+		<member name="rendering/gles2/batching/light_max_join_items" type="int" setter="" getter="" default="32">
+			Lights have the potential to prevent joining items, and break many of the performance benefits of batching. This setting enables some complex logic to allow joining items if their lighting is similar, and overlap tests pass. This can significantly improve performance in some games. Set to 0 to switch off. With large values the cost of overlap tests may lead to diminishing returns.
+		</member>
 		<member name="rendering/gles2/batching/light_scissor_area_threshold" type="float" setter="" getter="" default="1.0">
 			Sets the proportion of the screen area that must be saved by a scissor operation in order to activate light scissoring. This can prevent parts of items being rendered outside the light area. Lower values scissor more aggressively. A value of 1 scissors none of the items, a value of 0 scissors every item. This can reduce fill rate requirements in scenes with a lot of lighting.
 		</member>
 		<member name="rendering/gles2/batching/max_join_item_commands" type="int" setter="" getter="" default="16">
 			Sets the number of commands to lookahead to determine whether to batch render items. A value of 1 can join items consisting of single commands, 0 turns off joining. Higher values are in theory more likely to join, however this has diminishing returns and has a runtime cost so a small value is recommended.
 		</member>
+		<member name="rendering/gles2/batching/single_rect_fallback" type="bool" setter="" getter="" default="false">
+			Enabling this uses the legacy method to draw single rects, which is faster, but can cause flicker on some systems. This is best disabled unless crucial for performance.
+		</member>
 		<member name="rendering/gles2/batching/use_batching" type="bool" setter="" getter="" default="true">
 			Turns batching on and off. Batching increases performance by reducing the amount of graphics API drawcalls.
 		</member>

drivers/gles2/rasterizer_canvas_gles2.cpp

@@ -64,12 +64,18 @@ RasterizerCanvasGLES2::BatchData::BatchData() {
 	next_diagnose_tick = 10000;
 	diagnose_frame_number = 9999999999; // some high number
 	join_across_z_indices = true;
+	settings_item_reordering_lookahead = 0;
 
 	settings_use_batching_original_choice = false;
 	settings_flash_batching = false;
 	settings_diagnose_frame = false;
 	settings_scissor_lights = false;
 	settings_scissor_threshold = -1.0f;
+	settings_use_single_rect_fallback = false;
+	settings_light_max_join_items = 16;
+
+	stats_items_sorted = 0;
+	stats_light_items_joined = 0;
 }
 
 void RasterizerCanvasGLES2::RenderItemState::reset() {
@@ -317,7 +323,7 @@ bool RasterizerCanvasGLES2::prefill_joined_item(FillState &r_fill_state, int &r_
 					// because joined items with more than 1, the command * will be incorrect
 					// NOTE - this is assuming that use_hardware_transform means that it is a non-joined item!!
 					// If that assumption is incorrect this will go horribly wrong.
-					if (r_fill_state.use_hardware_transform) {
+					if (bdata.settings_use_single_rect_fallback && r_fill_state.use_hardware_transform) {
 						bool is_single_rect = false;
 						int command_num_next = command_num + 1;
 						if (command_num_next < command_count) {
@@ -1614,7 +1620,7 @@ void RasterizerCanvasGLES2::render_batches(Item::Command *const *p_commands, Ite
 	bdata.reset_flush();
 }
 
-void RasterizerCanvasGLES2::render_joined_item_commands(const BItemJoined &p_bij, Item *p_current_clip, bool &r_reclip, RasterizerStorageGLES2::Material *p_material) {
+void RasterizerCanvasGLES2::render_joined_item_commands(const BItemJoined &p_bij, Item *p_current_clip, bool &r_reclip, RasterizerStorageGLES2::Material *p_material, bool p_lit) {
 
 	Item *item = 0;
 	Item *first_item = bdata.item_refs[p_bij.first_item_ref].item;
@@ -1627,7 +1633,14 @@ void RasterizerCanvasGLES2::render_joined_item_commands(const BItemJoined &p_bij
 	for (unsigned int i = 0; i < p_bij.num_item_refs; i++) {
 		const BItemRef &ref = bdata.item_refs[p_bij.first_item_ref + i];
 		item = ref.item;
-		fill_state.final_modulate = ref.final_modulate;
+
+		if (!p_lit) {
+			// if not lit we use the complex calculated final modulate
+			fill_state.final_modulate = ref.final_modulate;
+		} else {
+			// if lit we ignore canvas modulate and just use the item modulate
+			fill_state.final_modulate = item->final_modulate;
+		}
 
 		int command_count = item->commands.size();
 		int command_start = 0;
@@ -1718,6 +1731,186 @@ void RasterizerCanvasGLES2::_canvas_item_render_commands(Item *p_item, Item *p_c
 	render_batches(commands, p_current_clip, r_reclip, p_material);
 }
 
+void RasterizerCanvasGLES2::record_items(Item *p_item_list, int p_z) {
+	while (p_item_list) {
+		BSortItem *s = bdata.sort_items.request_with_grow();
+
+		s->item = p_item_list;
+		s->z_index = p_z;
+
+		p_item_list = p_item_list->next;
+	}
+}
+
+void RasterizerCanvasGLES2::sort_items() {
+	// turned off?
+	if (!bdata.settings_item_reordering_lookahead) {
+		return;
+	}
+
+	for (int s = 0; s < bdata.sort_items.size() - 1; s++) {
+		if (sort_items_from(s)) {
+#ifdef DEBUG_ENABLED
+			bdata.stats_items_sorted++;
+#endif
+		}
+	}
+}
+
+bool RasterizerCanvasGLES2::sort_items_from(int p_start) {
+#ifdef DEBUG_ENABLED
+	ERR_FAIL_COND_V((p_start + 1) >= bdata.sort_items.size(), false)
+#endif
+
+	const BSortItem &start = bdata.sort_items[p_start];
+	int start_z = start.z_index;
+
+	// check start is the right type for sorting
+	if (start.item->commands.size() != 1) {
+		return false;
+	}
+	const Item::Command &command_start = *start.item->commands[0];
+	if (command_start.type != Item::Command::TYPE_RECT) {
+		return false;
+	}
+
+	BSortItem &second = bdata.sort_items[p_start + 1];
+	if (second.z_index != start_z) {
+		// no sorting across z indices (for now)
+		return false;
+	}
+
+	// if the neighbours are already a good match
+	if (_sort_items_match(start, second)) // order is crucial, start first
+	{
+		return false;
+	}
+
+	// if the start and 2nd items overlap, can do no more
+	if (start.item->global_rect_cache.intersects(second.item->global_rect_cache)) {
+		return false;
+	}
+
+	// which neighbour to test
+	int test_last = 2 + bdata.settings_item_reordering_lookahead;
+	for (int test = 2; test < test_last; test++) {
+		int test_sort_item_id = p_start + test;
+
+		// if we've got to the end of the list, can't sort any more, give up
+		if (test_sort_item_id >= bdata.sort_items.size()) {
+			return false;
+		}
+
+		BSortItem *test_sort_item = &bdata.sort_items[test_sort_item_id];
+
+		// across z indices?
+		if (test_sort_item->z_index != start_z) {
+			return false;
+		}
+
+		// do they match?
+		if (!_sort_items_match(start, *test_sort_item)) // order is crucial, start first
+		{
+			continue;
+		}
+
+		Item *test_item = test_sort_item->item;
+
+		// we can only swap if there are no AABB overlaps with sandwiched neighbours
+		bool ok = true;
+		for (int sn = 1; sn < test; sn++) {
+			BSortItem *sandwich_neighbour = &bdata.sort_items[p_start + sn];
+			if (test_item->global_rect_cache.intersects(sandwich_neighbour->item->global_rect_cache)) {
+				ok = false;
+				break;
+			}
+		}
+		if (!ok) {
+			continue;
+		}
+
+		// it is ok to exchange them!
+		BSortItem temp;
+		temp.assign(second);
+		second.assign(*test_sort_item);
+		test_sort_item->assign(temp);
+
+		return true;
+	} // for test
+
+	return false;
+}
+
+void RasterizerCanvasGLES2::join_sorted_items() {
+	sort_items();
+
+	int z = VS::CANVAS_ITEM_Z_MIN;
+	_render_item_state.item_group_z = z;
+
+	for (int s = 0; s < bdata.sort_items.size(); s++) {
+		const BSortItem &si = bdata.sort_items[s];
+		Item *ci = si.item;
+
+		// change z?
+		if (si.z_index != z) {
+			z = si.z_index;
+
+			// may not be required
+			_render_item_state.item_group_z = z;
+
+			// if z ranged lights are present, sometimes we have to disable joining over z_indices.
+			// we do this here.
+			// Note this restriction may be able to be relaxed with light bitfields, investigate!
+			if (!bdata.join_across_z_indices) {
+				_render_item_state.join_batch_break = true;
+			}
+		}
+
+		bool join;
+
+		if (_render_item_state.join_batch_break) {
+			// always start a new batch for this item
+			join = false;
+
+			// could be another batch break (i.e. prevent NEXT item from joining this)
+			// so we still need to run try_join_item
+			// even though we know join is false.
+			// also we need to run try_join_item for every item because it keeps the state up to date,
+			// if we didn't run it the state would be out of date.
+			try_join_item(ci, _render_item_state, _render_item_state.join_batch_break);
+		} else {
+			join = try_join_item(ci, _render_item_state, _render_item_state.join_batch_break);
+		}
+
+		// assume the first item will always return no join
+		if (!join) {
+			_render_item_state.joined_item = bdata.items_joined.request_with_grow();
+			_render_item_state.joined_item->first_item_ref = bdata.item_refs.size();
+			_render_item_state.joined_item->num_item_refs = 1;
+			_render_item_state.joined_item->bounding_rect = ci->global_rect_cache;
+			_render_item_state.joined_item->z_index = z;
+
+			// add the reference
+			BItemRef *r = bdata.item_refs.request_with_grow();
+			r->item = ci;
+			// we are storing final_modulate in advance per item reference
+			// for baking into vertex colors.
+			// this may not be ideal... as we are increasing the size of item reference,
+			// but it is stupidly complex to calculate later, which would probably be slower.
+			r->final_modulate = _render_item_state.final_modulate;
+		} else {
+			CRASH_COND(_render_item_state.joined_item == 0);
+			_render_item_state.joined_item->num_item_refs += 1;
+			_render_item_state.joined_item->bounding_rect = _render_item_state.joined_item->bounding_rect.merge(ci->global_rect_cache);
+
+			BItemRef *r = bdata.item_refs.request_with_grow();
+			r->item = ci;
+			r->final_modulate = _render_item_state.final_modulate;
+		}
+
+	} // for s through sort items
+}
+
 void RasterizerCanvasGLES2::join_items(Item *p_item_list, int p_z) {
 
 	_render_item_state.item_group_z = p_z;
@@ -1783,8 +1976,28 @@ void RasterizerCanvasGLES2::join_items(Item *p_item_list, int p_z) {
 	}
 }
 
+void RasterizerCanvasGLES2::canvas_end() {
+#ifdef DEBUG_ENABLED
+	if (bdata.diagnose_frame) {
+		bdata.frame_string += "canvas_end\n";
+		if (bdata.stats_items_sorted) {
+			bdata.frame_string += "\titems reordered: " + itos(bdata.stats_items_sorted) + "\n";
+		}
+		if (bdata.stats_light_items_joined) {
+			bdata.frame_string += "\tlight items joined: " + itos(bdata.stats_light_items_joined) + "\n";
+		}
+
+		print_line(bdata.frame_string);
+	}
+#endif
+
+	RasterizerCanvasBaseGLES2::canvas_end();
+}
+
 void RasterizerCanvasGLES2::canvas_begin() {
 	// diagnose_frame?
+	bdata.frame_string = ""; // just in case, always set this as we don't want a string leak in release...
+#ifdef DEBUG_ENABLED
 	if (bdata.settings_diagnose_frame) {
 		bdata.diagnose_frame = false;
 
@@ -1800,12 +2013,14 @@ void RasterizerCanvasGLES2::canvas_begin() {
 
 		if (frame == bdata.diagnose_frame_number) {
 			bdata.diagnose_frame = true;
+			bdata.reset_stats();
 		}
 
 		if (bdata.diagnose_frame) {
 			bdata.frame_string = "canvas_begin FRAME " + itos(frame) + "\n";
 		}
 	}
+#endif
 
 	RasterizerCanvasBaseGLES2::canvas_begin();
 }
@@ -1832,6 +2047,7 @@ void RasterizerCanvasGLES2::canvas_render_items_begin(const Color &p_modulate, L
 	_render_item_state.item_group_modulate = p_modulate;
 	_render_item_state.item_group_light = p_light;
 	_render_item_state.item_group_base_transform = p_base_transform;
+	_render_item_state.light_region.reset();
 
 	// batch break must be preserved over the different z indices,
 	// to prevent joining to an item on a previous index if not allowed
@@ -1841,15 +2057,24 @@ void RasterizerCanvasGLES2::canvas_render_items_begin(const Color &p_modulate, L
 	// joined z_index items can be wrongly classified with z ranged lights.
 	bdata.join_across_z_indices = true;
 
+	int light_count = 0;
 	while (p_light) {
+		light_count++;
+
 		if ((p_light->z_min != VS::CANVAS_ITEM_Z_MIN) || (p_light->z_max != VS::CANVAS_ITEM_Z_MAX)) {
 			// prevent joining across z indices. This would have caused visual regressions
 			bdata.join_across_z_indices = false;
-			break;
 		}
 
 		p_light = p_light->next_ptr;
 	}
+
+	// can't use the light region bitfield if there are too many lights
+	// hopefully most games won't blow this limit..
+	// if they do they will work but it won't batch join items just in case
+	if (light_count > 64) {
+		_render_item_state.light_region.too_many_lights = true;
+	}
 }
 
 void RasterizerCanvasGLES2::canvas_render_items_end() {
@@ -1857,9 +2082,13 @@ void RasterizerCanvasGLES2::canvas_render_items_end() {
 		return;
 	}
 
+	join_sorted_items();
+
+#ifdef DEBUG_ENABLED
 	if (bdata.diagnose_frame) {
 		bdata.frame_string += "items\n";
 	}
+#endif
 
 	// batching render is deferred until after going through all the z_indices, joining all the items
 	canvas_render_items_implementation(0, 0, _render_item_state.item_group_modulate,
@@ -1868,17 +2097,14 @@ void RasterizerCanvasGLES2::canvas_render_items_end() {
 
 	bdata.items_joined.reset();
 	bdata.item_refs.reset();
-
-	if (bdata.diagnose_frame) {
-		print_line(bdata.frame_string);
-	}
+	bdata.sort_items.reset();
 }
 
 void RasterizerCanvasGLES2::canvas_render_items(Item *p_item_list, int p_z, const Color &p_modulate, Light *p_light, const Transform2D &p_base_transform) {
 	// stage 1 : join similar items, so that their state changes are not repeated,
 	// and commands from joined items can be batched together
 	if (bdata.settings_use_batching) {
-		join_items(p_item_list, p_z);
+		record_items(p_item_list, p_z);
 		return;
 	}
 
@@ -2042,10 +2268,94 @@ bool RasterizerCanvasGLES2::try_join_item(Item *p_ci, RenderItemState &r_ris, bo
 		// it is possible, but not if they overlap, because
 		// a + light_blend + b + light_blend IS NOT THE SAME AS
 		// a + b + light_blend
-		join = false;
 
-		// we also dont want to allow joining this item with the next item, because the next item could have no lights!
-		r_batch_break = true;
+		bool light_allow_join = true;
+
+		// this is a quick getout if we have turned off light joining
+		if ((bdata.settings_light_max_join_items == 0) || r_ris.light_region.too_many_lights) {
+			light_allow_join = false;
+		} else {
+			// do light joining...
+
+			// first calculate the light bitfield
+			uint64_t light_bitfield = 0;
+			uint64_t shadow_bitfield = 0;
+			Light *light = r_ris.item_group_light;
+
+			int light_count = -1;
+			while (light) {
+				light_count++;
+				uint64_t light_bit = 1 << light_count;
+
+				// note that as a cost of batching, the light culling will be less effective
+				if (p_ci->light_mask & light->item_mask && r_ris.item_group_z >= light->z_min && r_ris.item_group_z <= light->z_max) {
+
+					// Note that with the above test, it is possible to also include a bound check.
+					// Tests so far have indicated better performance without it, but there may be reason to change this at a later stage,
+					// so I leave the line here for reference:
+					// && p_ci->global_rect_cache.intersects_transformed(light->xform_cache, light->rect_cache)) {
+
+					light_bitfield |= light_bit;
+
+					bool has_shadow = light->shadow_buffer.is_valid() && p_ci->light_mask & light->item_shadow_mask;
+
+					if (has_shadow) {
+						shadow_bitfield |= light_bit;
+					}
+				}
+
+				light = light->next_ptr;
+			}
+
+			// now compare to previous
+			if ((r_ris.light_region.light_bitfield != light_bitfield) || (r_ris.light_region.shadow_bitfield != shadow_bitfield)) {
+				light_allow_join = false;
+
+				r_ris.light_region.light_bitfield = light_bitfield;
+				r_ris.light_region.shadow_bitfield = shadow_bitfield;
+			} else {
+				// only do these checks if necessary
+				if (join && (!r_batch_break)) {
+
+					// we still can't join, even if the lights are exactly the same, if there is overlap between the previous and this item
+					if (r_ris.joined_item && light_bitfield) {
+						if ((int)r_ris.joined_item->num_item_refs <= bdata.settings_light_max_join_items) {
+							for (uint32_t r = 0; r < r_ris.joined_item->num_item_refs; r++) {
+								Item *pRefItem = bdata.item_refs[r_ris.joined_item->first_item_ref + r].item;
+								if (p_ci->global_rect_cache.intersects(pRefItem->global_rect_cache)) {
+									light_allow_join = false;
+									break;
+								}
+							}
+
+#ifdef DEBUG_ENABLED
+							if (light_allow_join) {
+								bdata.stats_light_items_joined++;
+							}
+#endif
+
+						} // if below max join items
+						else {
+							// just don't allow joining if above overlap check max items
+							light_allow_join = false;
+						}
+					}
+
+				} // if not batch broken already (no point in doing expensive overlap tests if not needed)
+			} // if bitfields don't match
+		} // if do light joining
+
+		if (!light_allow_join) {
+			// can't join
+			join = false;
+			// we also dont want to allow joining this item with the next item, because the next item could have no lights!
+			r_batch_break = true;
+		}
+
+	} else {
+		// can't join the next item if it has any lights as it will be by definition affected by different set of lights
+		r_ris.light_region.light_bitfield = 0;
+		r_ris.light_region.shadow_bitfield = 0;
 	}
 
 	if (reclip) {
@@ -2718,7 +3028,7 @@ void RasterizerCanvasGLES2::render_joined_item(const BItemJoined &p_bij, RenderI
 	// using software transform
 	if (!p_bij.use_hardware_transform()) {
 		state.uniforms.modelview_matrix = Transform2D();
-		// final_modulate will be baked per item ref and multiplied by a NULL final modulate in the shader
+		// final_modulate will be baked per item ref so the final_modulate can be an identity color
 		state.uniforms.final_modulate = Color(1, 1, 1, 1);
 	} else {
 		state.uniforms.modelview_matrix = ci->final_transform;
@@ -2730,7 +3040,7 @@ void RasterizerCanvasGLES2::render_joined_item(const BItemJoined &p_bij, RenderI
 	_set_uniforms();
 
 	if (unshaded || (state.uniforms.final_modulate.a > 0.001 && (!r_ris.shader_cache || r_ris.shader_cache->canvas_item.light_mode != RasterizerStorageGLES2::Shader::CanvasItem::LIGHT_MODE_LIGHT_ONLY) && !ci->light_masked))
-		render_joined_item_commands(p_bij, NULL, reclip, material_ptr);
+		render_joined_item_commands(p_bij, NULL, reclip, material_ptr, false);
 
 	r_ris.rebind_shader = true; // hacked in for now.
 
@@ -2739,7 +3049,11 @@ void RasterizerCanvasGLES2::render_joined_item(const BItemJoined &p_bij, RenderI
 		Light *light = r_ris.item_group_light;
 		bool light_used = false;
 		VS::CanvasLightMode mode = VS::CANVAS_LIGHT_MODE_ADD;
-		state.uniforms.final_modulate = ci->final_modulate; // remove the canvas modulate
+
+		// we leave this set to 1, 1, 1, 1 if using software because the colors are baked into the vertices
+		if (p_bij.use_hardware_transform()) {
+			state.uniforms.final_modulate = ci->final_modulate; // remove the canvas modulate
+		}
 
 		while (light) {
 
@@ -2820,10 +3134,10 @@ void RasterizerCanvasGLES2::render_joined_item(const BItemJoined &p_bij, RenderI
 				// this can greatly reduce fill rate ..
 				// at the cost of glScissor commands, so is optional
 				if (!bdata.settings_scissor_lights || r_ris.current_clip) {
-					render_joined_item_commands(p_bij, NULL, reclip, material_ptr);
+					render_joined_item_commands(p_bij, NULL, reclip, material_ptr, true);
 				} else {
 					bool scissor = _light_scissor_begin(p_bij.bounding_rect, light->xform_cache, light->rect_cache);
-					render_joined_item_commands(p_bij, NULL, reclip, material_ptr);
+					render_joined_item_commands(p_bij, NULL, reclip, material_ptr, true);
 					if (scissor) {
 						glDisable(GL_SCISSOR_TEST);
 					}
@@ -2980,6 +3294,9 @@ void RasterizerCanvasGLES2::initialize() {
 	bdata.settings_use_batching = GLOBAL_GET("rendering/gles2/batching/use_batching");
 	bdata.settings_max_join_item_commands = GLOBAL_GET("rendering/gles2/batching/max_join_item_commands");
 	bdata.settings_colored_vertex_format_threshold = GLOBAL_GET("rendering/gles2/batching/colored_vertex_format_threshold");
+	bdata.settings_item_reordering_lookahead = GLOBAL_GET("rendering/gles2/batching/item_reordering_lookahead");
+	bdata.settings_light_max_join_items = GLOBAL_GET("rendering/gles2/batching/light_max_join_items");
+	bdata.settings_use_single_rect_fallback = GLOBAL_GET("rendering/gles2/batching/single_rect_fallback");
 
 	// we can use the threshold to determine whether to turn scissoring off or on
 	bdata.settings_scissor_threshold = GLOBAL_GET("rendering/gles2/batching/light_scissor_area_threshold");
@@ -2999,6 +3316,17 @@ void RasterizerCanvasGLES2::initialize() {
 	if (Engine::get_singleton()->is_editor_hint()) {
 		bool use_in_editor = GLOBAL_GET("rendering/gles2/debug/use_batching_in_editor");
 		bdata.settings_use_batching = use_in_editor;
+
+		// fix some settings in the editor, as the performance not worth the risk
+		bdata.settings_use_single_rect_fallback = false;
+	}
+
+	// if we are using batching, we will purposefully disable the nvidia workaround.
+	// This is because the only reason to use the single rect fallback is the approx 2x speed
+	// of the uniform drawing technique. If we used nvidia workaround, speed would be
+	// approx equal to the batcher drawing technique (indexed primitive + VB).
+	if (bdata.settings_use_batching) {
+		use_nvidia_rect_workaround = false;
 	}
 
 	// For debugging, if flash is set in project settings, it will flash on alternate frames
@@ -3035,21 +3363,31 @@ void RasterizerCanvasGLES2::initialize() {
 	bdata.settings_max_join_item_commands = CLAMP(bdata.settings_max_join_item_commands, 0, 65535);
 	bdata.settings_colored_vertex_format_threshold = CLAMP(bdata.settings_colored_vertex_format_threshold, 0.0f, 1.0f);
 	bdata.settings_scissor_threshold = CLAMP(bdata.settings_scissor_threshold, 0.0f, 1.0f);
+	bdata.settings_light_max_join_items = CLAMP(bdata.settings_light_max_join_items, 0, 65535);
+	bdata.settings_item_reordering_lookahead = CLAMP(bdata.settings_item_reordering_lookahead, 0, 65535);
 
 	// for debug purposes, output a string with the batching options
 	String batching_options_string = "OpenGL ES 2.0 Batching: ";
 	if (bdata.settings_use_batching) {
-		batching_options_string += "ON\n\tOPTIONS\n";
-		batching_options_string += "\tmax_join_item_commands " + itos(bdata.settings_max_join_item_commands) + "\n";
-		batching_options_string += "\tcolored_vertex_format_threshold " + String(Variant(bdata.settings_colored_vertex_format_threshold)) + "\n";
-		batching_options_string += "\tbatch_buffer_size " + itos(bdata.settings_batch_buffer_num_verts) + "\n";
-		batching_options_string += "\tlight_scissor_area_threshold " + String(Variant(bdata.settings_scissor_threshold)) + "\n";
-		batching_options_string += "\tdebug_flash " + String(Variant(bdata.settings_flash_batching)) + "\n";
-		batching_options_string += "\tdiagnose_frame " + String(Variant(bdata.settings_diagnose_frame));
-	} else {
-		batching_options_string += "OFF";
+		batching_options_string += "ON";
+
+		if (OS::get_singleton()->is_stdout_verbose()) {
+			batching_options_string += "\n\tOPTIONS\n";
+			batching_options_string += "\tmax_join_item_commands " + itos(bdata.settings_max_join_item_commands) + "\n";
+			batching_options_string += "\tcolored_vertex_format_threshold " + String(Variant(bdata.settings_colored_vertex_format_threshold)) + "\n";
+			batching_options_string += "\tbatch_buffer_size " + itos(bdata.settings_batch_buffer_num_verts) + "\n";
+			batching_options_string += "\tlight_scissor_area_threshold " + String(Variant(bdata.settings_scissor_threshold)) + "\n";
+
+			batching_options_string += "\titem_reordering_lookahead " + itos(bdata.settings_item_reordering_lookahead) + "\n";
+			batching_options_string += "\tlight_max_join_items " + itos(bdata.settings_light_max_join_items) + "\n";
+			batching_options_string += "\tsingle_rect_fallback " + String(Variant(bdata.settings_use_single_rect_fallback)) + "\n";
+
+			batching_options_string += "\tdebug_flash " + String(Variant(bdata.settings_flash_batching)) + "\n";
+			batching_options_string += "\tdiagnose_frame " + String(Variant(bdata.settings_diagnose_frame));
+		}
+
+		print_line(batching_options_string);
 	}
-	print_line(batching_options_string);
 
 	// special case, for colored vertex format threshold.
 	// as the comparison is >=, we want to be able to totally turn on or off

drivers/gles2/rasterizer_canvas_gles2.h

@@ -115,6 +115,17 @@ class RasterizerCanvasGLES2 : public RasterizerCanvasBaseGLES2 {
 		BatchVector2 tex_pixel_size;
 	};
 
+	// items in a list to be sorted prior to joining
+	struct BSortItem {
+		// have a function to keep as pod, rather than operator
+		void assign(const BSortItem &o) {
+			item = o.item;
+			z_index = o.z_index;
+		}
+		Item *item;
+		int z_index;
+	};
+
 	// batch item may represent 1 or more items
 	struct BItemJoined {
 		uint32_t first_item_ref;
@@ -136,6 +147,17 @@ class RasterizerCanvasGLES2 : public RasterizerCanvasBaseGLES2 {
 		Color final_modulate;
 	};
 
+	struct BLightRegion {
+		void reset() {
+			light_bitfield = 0;
+			shadow_bitfield = 0;
+			too_many_lights = false;
+		}
+		uint64_t light_bitfield;
+		uint64_t shadow_bitfield;
+		bool too_many_lights; // we can only do light region optimization if there are 64 or less lights
+	};
+
 	struct BatchData {
 		BatchData();
 		void reset_flush() {
@@ -167,6 +189,9 @@ class RasterizerCanvasGLES2 : public RasterizerCanvasBaseGLES2 {
 		RasterizerArrayGLES2<BItemJoined> items_joined;
 		RasterizerArrayGLES2<BItemRef> item_refs;
 
+		// items are sorted prior to joining
+		RasterizerArrayGLES2<BSortItem> sort_items;
+
 		// counts
 		int total_quads;
 
@@ -198,6 +223,19 @@ class RasterizerCanvasGLES2 : public RasterizerCanvasBaseGLES2 {
 		int settings_batch_buffer_num_verts;
 		bool settings_scissor_lights;
 		float settings_scissor_threshold; // 0.0 to 1.0
+		int settings_item_reordering_lookahead;
+		bool settings_use_single_rect_fallback;
+		int settings_light_max_join_items;
+
+		// only done on diagnose frame
+		void reset_stats() {
+			stats_items_sorted = 0;
+			stats_light_items_joined = 0;
+		}
+
+		// frame stats (just for monitoring and debugging)
+		int stats_items_sorted;
+		int stats_light_items_joined;
 	} bdata;
 
 	struct RenderItemState {
@@ -214,6 +252,7 @@ class RasterizerCanvasGLES2 : public RasterizerCanvasBaseGLES2 {
 		// used for joining items only
 		BItemJoined *joined_item;
 		bool join_batch_break;
+		BLightRegion light_region;
 
 		// 'item group' is data over a single call to canvas_render_items
 		int item_group_z;
@@ -249,6 +288,7 @@ public:
 	virtual void canvas_render_items_end();
 	virtual void canvas_render_items(Item *p_item_list, int p_z, const Color &p_modulate, Light *p_light, const Transform2D &p_base_transform);
 	virtual void canvas_begin();
+	virtual void canvas_end();
 
 private:
 	// legacy codepath .. to remove after testing
@@ -258,9 +298,11 @@ private:
 	// high level batch funcs
 	void canvas_render_items_implementation(Item *p_item_list, int p_z, const Color &p_modulate, Light *p_light, const Transform2D &p_base_transform);
 	void render_joined_item(const BItemJoined &p_bij, RenderItemState &r_ris);
+	void record_items(Item *p_item_list, int p_z);
 	void join_items(Item *p_item_list, int p_z);
+	void join_sorted_items();
 	bool try_join_item(Item *p_ci, RenderItemState &r_ris, bool &r_batch_break);
-	void render_joined_item_commands(const BItemJoined &p_bij, Item *p_current_clip, bool &r_reclip, RasterizerStorageGLES2::Material *p_material);
+	void render_joined_item_commands(const BItemJoined &p_bij, Item *p_current_clip, bool &r_reclip, RasterizerStorageGLES2::Material *p_material, bool p_lit);
 	void render_batches(Item::Command *const *p_commands, Item *p_current_clip, bool &r_reclip, RasterizerStorageGLES2::Material *p_material);
 	bool prefill_joined_item(FillState &r_fill_state, int &r_command_start, Item *p_item, Item *p_current_clip, bool &r_reclip, RasterizerStorageGLES2::Material *p_material);
 	void flush_render_batches(Item *p_first_item, Item *p_current_clip, bool &r_reclip, RasterizerStorageGLES2::Material *p_material);
@@ -280,6 +322,11 @@ private:
 	TransformMode _find_transform_mode(const Transform2D &p_tr) const;
 	_FORCE_INLINE_ void _prefill_default_batch(FillState &r_fill_state, int p_command_num, const Item &p_item);
 
+	// sorting
+	void sort_items();
+	bool sort_items_from(int p_start);
+	bool _sort_items_match(const BSortItem &p_a, const BSortItem &p_b) const;
+
 	// light scissoring
 	bool _light_find_intersection(const Rect2 &p_item_rect, const Transform2D &p_light_xform, const Rect2 &p_light_rect, Rect2 &r_cliprect) const;
 	bool _light_scissor_begin(const Rect2 &p_item_rect, const Transform2D &p_light_xform, const Rect2 &p_light_rect) const;
@@ -392,4 +439,33 @@ _FORCE_INLINE_ RasterizerCanvasGLES2::TransformMode RasterizerCanvasGLES2::_find
 	return TM_ALL;
 }
 
+_FORCE_INLINE_ bool RasterizerCanvasGLES2::_sort_items_match(const BSortItem &p_a, const BSortItem &p_b) const {
+	const Item *a = p_a.item;
+	const Item *b = p_b.item;
+
+	if (b->commands.size() != 1)
+		return false;
+
+	// tested outside function
+	//	if (a->commands.size() != 1)
+	//		return false;
+
+	const Item::Command &cb = *b->commands[0];
+	if (cb.type != Item::Command::TYPE_RECT)
+		return false;
+
+	const Item::Command &ca = *a->commands[0];
+	// tested outside function
+	//	if (ca.type != Item::Command::TYPE_RECT)
+	//		return false;
+
+	const Item::CommandRect *rect_a = static_cast<const Item::CommandRect *>(&ca);
+	const Item::CommandRect *rect_b = static_cast<const Item::CommandRect *>(&cb);
+
+	if (rect_a->texture != rect_b->texture)
+		return false;
+
+	return true;
+}
+
 #endif // RASTERIZERCANVASGLES2_H

servers/visual_server.cpp

@@ -2420,7 +2420,10 @@ VisualServer::VisualServer() {
 	GLOBAL_DEF("rendering/gles2/batching/max_join_item_commands", 16);
 	GLOBAL_DEF("rendering/gles2/batching/colored_vertex_format_threshold", 0.25f);
 	GLOBAL_DEF("rendering/gles2/batching/light_scissor_area_threshold", 1.0f);
+	GLOBAL_DEF("rendering/gles2/batching/light_max_join_items", 32);
 	GLOBAL_DEF("rendering/gles2/batching/batch_buffer_size", 16384);
+	GLOBAL_DEF("rendering/gles2/batching/item_reordering_lookahead", 4);
+	GLOBAL_DEF("rendering/gles2/batching/single_rect_fallback", false);
 	GLOBAL_DEF("rendering/gles2/debug/flash_batching", false);
 	GLOBAL_DEF("rendering/gles2/debug/diagnose_frame", false);
 	GLOBAL_DEF_RST("rendering/gles2/debug/use_batching_in_editor", true);
@@ -2429,6 +2432,8 @@ VisualServer::VisualServer() {
 	ProjectSettings::get_singleton()->set_custom_property_info("rendering/gles2/batching/colored_vertex_format_threshold", PropertyInfo(Variant::REAL, "rendering/gles2/batching/colored_vertex_format_threshold", PROPERTY_HINT_RANGE, "0.0,1.0,0.01"));
 	ProjectSettings::get_singleton()->set_custom_property_info("rendering/gles2/batching/batch_buffer_size", PropertyInfo(Variant::INT, "rendering/gles2/batching/batch_buffer_size", PROPERTY_HINT_RANGE, "1024,65535,1024"));
 	ProjectSettings::get_singleton()->set_custom_property_info("rendering/gles2/batching/light_scissor_area_threshold", PropertyInfo(Variant::REAL, "rendering/gles2/batching/light_scissor_area_threshold", PROPERTY_HINT_RANGE, "0.0,1.0"));
+	ProjectSettings::get_singleton()->set_custom_property_info("rendering/gles2/batching/light_max_join_items", PropertyInfo(Variant::INT, "rendering/gles2/batching/light_max_join_items", PROPERTY_HINT_RANGE, "0,512"));
+	ProjectSettings::get_singleton()->set_custom_property_info("rendering/gles2/batching/item_reordering_lookahead", PropertyInfo(Variant::INT, "rendering/gles2/batching/item_reordering_lookahead", PROPERTY_HINT_RANGE, "0,256"));
 }
 
 VisualServer::~VisualServer() {