Enable geometry fade/transparency in the Mobile renderer

This is mostly a copy-paste of similar changes in the Forward+ renderer,
as hinted in godotengine#76774 (comment) and godotengine#87231 (review),
along with a tweak to the shader and pipeline model.

The shader pipeline tweak involves distinguishing geometry instance-enabled
transparency from material-enabled transparency. A material cannot support
transparency on a per-instance level; a separate pipeline must be used when rendering.

Originally in c571e4a this was a non-trivial refactoring in Forward+
(which in the past few years has evolved a few more times to account for the multitude of combinations
allowed there).

I opted to follow a similar sentiment to `SceneShaderForwardClustered::PipelineColorPassFlags`
in a simpler `SceneShaderForwardMobile::PipelinePasses` enum, which only accounts
for don't-care or opaque pipelines vs. color transparency-enabled ones.

This multiplies the number of `PipelineCacheRD`s by two, but otherwise accomplishes
the goals without adding unnecessary changes or shooting myself or others in the foot (I hope).

BTW I also reorganized and removed some redundant checks in
`RenderForwardClustered::_geometry_instance_add_surface_with_material`
(since I was comparing this side-by-side with the `RenderForwardMobile` version, which seems
better-organized). There is no functional change since `has_alpha` is the only variable used
and includes all the checks anyway.

doc/classes/GeometryInstance3D.xml

@@ -66,7 +66,7 @@
 			The transparency applied to the whole geometry (as a multiplier of the materials' existing transparency). [code]0.0[/code] is fully opaque, while [code]1.0[/code] is fully transparent. Values greater than [code]0.0[/code] (exclusive) will force the geometry's materials to go through the transparent pipeline, which is slower to render and can exhibit rendering issues due to incorrect transparency sorting. However, unlike using a transparent material, setting [member transparency] to a value greater than [code]0.0[/code] (exclusive) will [i]not[/i] disable shadow rendering.
 			In spatial shaders, [code]1.0 - transparency[/code] is set as the default value of the [code]ALPHA[/code] built-in.
 			[b]Note:[/b] [member transparency] is clamped between [code]0.0[/code] and [code]1.0[/code], so this property cannot be used to make transparent materials more opaque than they originally are.
-			[b]Note:[/b] Only supported when using the Forward+ rendering method. When using the Mobile or Compatibility rendering method, [member transparency] is ignored and is considered as always being [code]0.0[/code].
+			[b]Note:[/b] Only supported when using the Forward+ or Mobile rendering methods. When using the Compatibility rendering method, [member transparency] is ignored and is considered as always being [code]0.0[/code].
 		</member>
 		<member name="visibility_range_begin" type="float" setter="set_visibility_range_begin" getter="get_visibility_range_begin" default="0.0" keywords="lod_begin, hlod_begin">
 			Starting distance from which the GeometryInstance3D will be visible, taking [member visibility_range_begin_margin] into account as well. The default value of 0 is used to disable the range check.
@@ -131,11 +131,11 @@
 		</constant>
 		<constant name="VISIBILITY_RANGE_FADE_SELF" value="1" enum="VisibilityRangeFadeMode">
 			Will fade-out itself when reaching the limits of its own visibility range. This is slower than [constant VISIBILITY_RANGE_FADE_DISABLED], but it can provide smoother transitions. The fading range is determined by [member visibility_range_begin_margin] and [member visibility_range_end_margin].
-			[b]Note:[/b] Only supported when using the Forward+ rendering method. When using the Mobile or Compatibility rendering method, this mode acts like [constant VISIBILITY_RANGE_FADE_DISABLED] but with hysteresis disabled.
+			[b]Note:[/b] Only supported when using the Forward+ or Mobile rendering methods. When using the Compatibility rendering method, this mode acts like [constant VISIBILITY_RANGE_FADE_DISABLED] but with hysteresis disabled.
 		</constant>
 		<constant name="VISIBILITY_RANGE_FADE_DEPENDENCIES" value="2" enum="VisibilityRangeFadeMode">
 			Will fade-in its visibility dependencies (see [member Node3D.visibility_parent]) when reaching the limits of its own visibility range. This is slower than [constant VISIBILITY_RANGE_FADE_DISABLED], but it can provide smoother transitions. The fading range is determined by [member visibility_range_begin_margin] and [member visibility_range_end_margin].
-			[b]Note:[/b] Only supported when using the Forward+ rendering method. When using the Mobile or Compatibility rendering method, this mode acts like [constant VISIBILITY_RANGE_FADE_DISABLED] but with hysteresis disabled.
+			[b]Note:[/b] Only supported when using the Forward+ or Mobile rendering methods. When using the Compatibility rendering method, this mode acts like [constant VISIBILITY_RANGE_FADE_DISABLED] but with hysteresis disabled.
 		</constant>
 	</constants>
 </class>

scene/3d/visual_instance_3d.cpp

@@ -439,12 +439,12 @@ PackedStringArray GeometryInstance3D::get_configuration_warnings() const {
 		warnings.push_back(RTR("The GeometryInstance3D is configured to fade out smoothly over distance, but the fade transition distance is set to 0.\nTo resolve this, increase Visibility Range End Margin above 0."));
 	}
 
-	if (!Math::is_zero_approx(transparency) && OS::get_singleton()->get_current_rendering_method() != "forward_plus") {
-		warnings.push_back(RTR("GeometryInstance3D transparency is only available when using the Forward+ rendering method."));
+	if (!Math::is_zero_approx(transparency) && OS::get_singleton()->get_current_rendering_method() == "gl_compatibility") {
+		warnings.push_back(RTR("GeometryInstance3D transparency is only available when using the Forward+ or Mobile rendering methods."));
 	}
 
-	if ((visibility_range_fade_mode == VISIBILITY_RANGE_FADE_SELF || visibility_range_fade_mode == VISIBILITY_RANGE_FADE_DEPENDENCIES) && OS::get_singleton()->get_current_rendering_method() != "forward_plus") {
-		warnings.push_back(RTR("GeometryInstance3D visibility range transparency fade is only available when using the Forward+ rendering method."));
+	if ((visibility_range_fade_mode == VISIBILITY_RANGE_FADE_SELF || visibility_range_fade_mode == VISIBILITY_RANGE_FADE_DEPENDENCIES) && OS::get_singleton()->get_current_rendering_method() == "gl_compatibility") {
+		warnings.push_back(RTR("GeometryInstance3D visibility range transparency fade is only available when using the Forward+ or Mobile rendering methods."));
 	}
 
 	return warnings;

servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp

@@ -3730,9 +3730,9 @@ void RenderForwardClustered::_geometry_instance_add_surface_with_material(Geomet
 	RendererRD::MeshStorage *mesh_storage = RendererRD::MeshStorage::get_singleton();
 
 	bool has_read_screen_alpha = p_material->shader_data->uses_screen_texture || p_material->shader_data->uses_depth_texture || p_material->shader_data->uses_normal_texture;
-	bool has_base_alpha = (p_material->shader_data->uses_alpha && (!p_material->shader_data->uses_alpha_clip || p_material->shader_data->uses_alpha_antialiasing)) || has_read_screen_alpha;
+	bool has_base_alpha = (p_material->shader_data->uses_alpha && (!p_material->shader_data->uses_alpha_clip || p_material->shader_data->uses_alpha_antialiasing));
 	bool has_blend_alpha = p_material->shader_data->uses_blend_alpha;
-	bool has_alpha = has_base_alpha || has_blend_alpha;
+	bool has_alpha = has_base_alpha || has_blend_alpha || has_read_screen_alpha;
 
 	uint32_t flags = 0;
 
@@ -3756,7 +3756,7 @@ void RenderForwardClustered::_geometry_instance_add_surface_with_material(Geomet
 		flags |= GeometryInstanceSurfaceDataCache::FLAG_USES_DOUBLE_SIDED_SHADOWS;
 	}
 
-	if (has_alpha || has_read_screen_alpha || p_material->shader_data->depth_draw == SceneShaderForwardClustered::ShaderData::DEPTH_DRAW_DISABLED || p_material->shader_data->depth_test == SceneShaderForwardClustered::ShaderData::DEPTH_TEST_DISABLED) {
+	if (has_alpha || p_material->shader_data->depth_draw == SceneShaderForwardClustered::ShaderData::DEPTH_DRAW_DISABLED || p_material->shader_data->depth_test == SceneShaderForwardClustered::ShaderData::DEPTH_TEST_DISABLED) {
 		//material is only meant for alpha pass
 		flags |= GeometryInstanceSurfaceDataCache::FLAG_PASS_ALPHA;
 		if ((p_material->shader_data->uses_depth_prepass_alpha || p_material->shader_data->uses_alpha_antialiasing) && !(p_material->shader_data->depth_draw == SceneShaderForwardClustered::ShaderData::DEPTH_DRAW_DISABLED || p_material->shader_data->depth_test == SceneShaderForwardClustered::ShaderData::DEPTH_TEST_DISABLED)) {

servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp

@@ -1078,7 +1078,7 @@ void RenderForwardMobile::_render_scene(RenderDataRD *p_render_data, const Color
 				// this may be needed if we re-introduced steps that change info, not sure which do so in the previous implementation
 				//_setup_environment(p_render_data, is_reflection_probe, screen_size, !is_reflection_probe, p_default_bg_color, false);
 
-				RenderListParameters render_list_params(render_list[RENDER_LIST_ALPHA].elements.ptr(), render_list[RENDER_LIST_ALPHA].element_info.ptr(), render_list[RENDER_LIST_ALPHA].elements.size(), reverse_cull, PASS_MODE_COLOR, rp_uniform_set, spec_constant_base_flags, get_debug_draw_mode() == RS::VIEWPORT_DEBUG_DRAW_WIREFRAME, Vector2(), p_render_data->scene_data->lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, p_render_data->scene_data->view_count);
+				RenderListParameters render_list_params(render_list[RENDER_LIST_ALPHA].elements.ptr(), render_list[RENDER_LIST_ALPHA].element_info.ptr(), render_list[RENDER_LIST_ALPHA].elements.size(), reverse_cull, PASS_MODE_COLOR_TRANSPARENT, rp_uniform_set, spec_constant_base_flags, get_debug_draw_mode() == RS::VIEWPORT_DEBUG_DRAW_WIREFRAME, Vector2(), p_render_data->scene_data->lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, p_render_data->scene_data->view_count);
 				render_list_params.framebuffer_format = fb_format;
 				render_list_params.subpass = RD::get_singleton()->draw_list_get_current_pass(); // Should now always be 0.
 
@@ -1830,6 +1830,20 @@ void RenderForwardMobile::_fill_render_list(RenderListType p_render_list, const
 
 		bool uses_lightmap = false;
 		// bool uses_gi = false;
+		float fade_alpha = 1.0;
+
+		if (inst->fade_near || inst->fade_far) {
+			float fade_dist = inst->transform.origin.distance_to(p_render_data->scene_data->cam_transform.origin);
+			// Use `smoothstep()` to make opacity changes more gradual and less noticeable to the player.
+			if (inst->fade_far && fade_dist > inst->fade_far_begin) {
+				fade_alpha = Math::smoothstep(0.0f, 1.0f, 1.0f - (fade_dist - inst->fade_far_begin) / (inst->fade_far_end - inst->fade_far_begin));
+			} else if (inst->fade_near && fade_dist < inst->fade_near_end) {
+				fade_alpha = Math::smoothstep(0.0f, 1.0f, (fade_dist - inst->fade_near_begin) / (inst->fade_near_end - inst->fade_near_begin));
+			}
+		}
+
+		fade_alpha *= inst->force_alpha * inst->parent_fade_alpha;
+		flags |= (uint32_t(fade_alpha * 255.0) << INSTANCE_DATA_FLAGS_FADE_SHIFT) & INSTANCE_DATA_FLAGS_FADE_MASK;
 
 		if (p_render_list == RENDER_LIST_OPAQUE) {
 			if (inst->lightmap_instance.is_valid()) {
@@ -1935,6 +1949,11 @@ void RenderForwardMobile::_fill_render_list(RenderListType p_render_list, const
 #else
 				bool force_alpha = false;
 #endif
+
+				if (fade_alpha < 0.999) {
+					force_alpha = true;
+				}
+
 				if (!force_alpha && (surf->flags & GeometryInstanceSurfaceDataCache::FLAG_PASS_OPAQUE)) {
 					rl->add_element(surf);
 				}
@@ -2146,6 +2165,7 @@ void RenderForwardMobile::_render_list_template(RenderingDevice::DrawListID p_dr
 		RID xforms_uniform_set = surf->owner->transforms_uniform_set;
 
 		SceneShaderForwardMobile::ShaderVersion shader_version = SceneShaderForwardMobile::SHADER_VERSION_MAX; // Assigned to silence wrong -Wmaybe-initialized.
+		SceneShaderForwardMobile::PipelinePasses color_pass = SceneShaderForwardMobile::PIPELINE_PASS_NOT_COLOR_OR_OPAQUE;
 
 		switch (p_params->pass_mode) {
 			case PASS_MODE_COLOR:
@@ -2155,6 +2175,9 @@ void RenderForwardMobile::_render_list_template(RenderingDevice::DrawListID p_dr
 				} else {
 					shader_version = p_params->view_count > 1 ? SceneShaderForwardMobile::SHADER_VERSION_COLOR_PASS_MULTIVIEW : SceneShaderForwardMobile::SHADER_VERSION_COLOR_PASS;
 				}
+				if (p_params->pass_mode == PASS_MODE_COLOR_TRANSPARENT) {
+					color_pass = SceneShaderForwardMobile::PIPELINE_PASS_COLOR_TRANSPARENT;
+				}
 			} break;
 			case PASS_MODE_SHADOW: {
 				shader_version = p_params->view_count > 1 ? SceneShaderForwardMobile::SHADER_VERSION_SHADOW_PASS_MULTIVIEW : SceneShaderForwardMobile::SHADER_VERSION_SHADOW_PASS;
@@ -2171,7 +2194,7 @@ void RenderForwardMobile::_render_list_template(RenderingDevice::DrawListID p_dr
 
 		PipelineCacheRD *pipeline = nullptr;
 
-		pipeline = &shader->pipelines[cull_variant][primitive][shader_version];
+		pipeline = &shader->pipelines[cull_variant][primitive][shader_version][color_pass];
 
 		RD::VertexFormatID vertex_format = -1;
 		RID vertex_array_rd;

servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.h

@@ -393,6 +393,8 @@ class RenderForwardMobile : public RendererSceneRenderRD {
 		INSTANCE_DATA_FLAG_MULTIMESH_HAS_CUSTOM_DATA = 1 << 15,
 		INSTANCE_DATA_FLAGS_PARTICLE_TRAIL_SHIFT = 16,
 		INSTANCE_DATA_FLAGS_PARTICLE_TRAIL_MASK = 0xFF,
+		INSTANCE_DATA_FLAGS_FADE_SHIFT = 24,
+		INSTANCE_DATA_FLAGS_FADE_MASK = 0xFFUL << INSTANCE_DATA_FLAGS_FADE_SHIFT
 	};
 
 	struct GeometryInstanceLightmapSH {

servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.cpp

@@ -314,46 +314,49 @@ void SceneShaderForwardMobile::ShaderData::set_code(const String &p_code) {
 				raster_state.cull_mode = cull_mode_rd;
 				raster_state.wireframe = wireframe;
 
-				RD::PipelineColorBlendState blend_state;
-				RD::PipelineDepthStencilState depth_stencil = depth_stencil_state;
-				RD::PipelineMultisampleState multisample_state;
-
-				if (uses_alpha || uses_blend_alpha) {
-					// only allow these flags to go through if we have some form of msaa
-					if (alpha_antialiasing_mode == ALPHA_ANTIALIASING_ALPHA_TO_COVERAGE) {
-						multisample_state.enable_alpha_to_coverage = true;
-					} else if (alpha_antialiasing_mode == ALPHA_ANTIALIASING_ALPHA_TO_COVERAGE_AND_TO_ONE) {
-						multisample_state.enable_alpha_to_coverage = true;
-						multisample_state.enable_alpha_to_one = true;
-					}
+				for (int l = 0; l < PIPELINE_PASS_COUNT; l++) {
+					RD::PipelineColorBlendState blend_state;
+					RD::PipelineDepthStencilState depth_stencil = depth_stencil_state;
+					RD::PipelineMultisampleState multisample_state;
+
+					if (l == PIPELINE_PASS_COLOR_TRANSPARENT) {
+						// only allow these flags to go through if we have some form of msaa
+						if (alpha_antialiasing_mode == ALPHA_ANTIALIASING_ALPHA_TO_COVERAGE) {
+							multisample_state.enable_alpha_to_coverage = true;
+						} else if (alpha_antialiasing_mode == ALPHA_ANTIALIASING_ALPHA_TO_COVERAGE_AND_TO_ONE) {
+							multisample_state.enable_alpha_to_coverage = true;
+							multisample_state.enable_alpha_to_one = true;
+						}
 
-					if (k == SHADER_VERSION_COLOR_PASS || k == SHADER_VERSION_COLOR_PASS_MULTIVIEW || k == SHADER_VERSION_LIGHTMAP_COLOR_PASS || k == SHADER_VERSION_LIGHTMAP_COLOR_PASS_MULTIVIEW) {
-						blend_state = blend_state_blend;
-						if (depth_draw == DEPTH_DRAW_OPAQUE && !uses_alpha_clip) {
-							depth_stencil.enable_depth_write = false; //alpha does not draw depth
+						if (k == SHADER_VERSION_COLOR_PASS || k == SHADER_VERSION_COLOR_PASS_MULTIVIEW || k == SHADER_VERSION_LIGHTMAP_COLOR_PASS || k == SHADER_VERSION_LIGHTMAP_COLOR_PASS_MULTIVIEW) {
+							blend_state = blend_state_blend;
+							if (depth_draw == DEPTH_DRAW_OPAQUE && !uses_alpha_clip) {
+								depth_stencil.enable_depth_write = false; //alpha does not draw depth
+							}
+						} else if (k == SHADER_VERSION_SHADOW_PASS || k == SHADER_VERSION_SHADOW_PASS_MULTIVIEW || k == SHADER_VERSION_SHADOW_PASS_DP) {
+							//none, blend state contains nothing
+						} else if (k == SHADER_VERSION_DEPTH_PASS_WITH_MATERIAL) {
+							blend_state = RD::PipelineColorBlendState::create_disabled(5); //writes to normal and roughness in opaque way
+						} else {
+							pipelines[i][j][k][l].clear();
+							continue; // do not use this version (will error if using it is attempted)
+						}
+					} else { // PIPELINE_PASS_NOT_COLOR_OR_OPAQUE
+
+						if (k == SHADER_VERSION_COLOR_PASS || k == SHADER_VERSION_COLOR_PASS_MULTIVIEW || k == SHADER_VERSION_LIGHTMAP_COLOR_PASS || k == SHADER_VERSION_LIGHTMAP_COLOR_PASS_MULTIVIEW) {
+							blend_state = blend_state_opaque;
+						} else if (k == SHADER_VERSION_SHADOW_PASS || k == SHADER_VERSION_SHADOW_PASS_MULTIVIEW || k == SHADER_VERSION_SHADOW_PASS_DP) {
+							//none, leave empty
+						} else if (k == SHADER_VERSION_DEPTH_PASS_WITH_MATERIAL) {
+							blend_state = RD::PipelineColorBlendState::create_disabled(5); //writes to normal and roughness in opaque way
+						} else {
+							// ???
 						}
-					} else if (k == SHADER_VERSION_SHADOW_PASS || k == SHADER_VERSION_SHADOW_PASS_MULTIVIEW || k == SHADER_VERSION_SHADOW_PASS_DP) {
-						//none, blend state contains nothing
-					} else if (k == SHADER_VERSION_DEPTH_PASS_WITH_MATERIAL) {
-						blend_state = RD::PipelineColorBlendState::create_disabled(5); //writes to normal and roughness in opaque way
-					} else {
-						pipelines[i][j][k].clear();
-						continue; // do not use this version (will error if using it is attempted)
-					}
-				} else {
-					if (k == SHADER_VERSION_COLOR_PASS || k == SHADER_VERSION_COLOR_PASS_MULTIVIEW || k == SHADER_VERSION_LIGHTMAP_COLOR_PASS || k == SHADER_VERSION_LIGHTMAP_COLOR_PASS_MULTIVIEW) {
-						blend_state = blend_state_opaque;
-					} else if (k == SHADER_VERSION_SHADOW_PASS || k == SHADER_VERSION_SHADOW_PASS_MULTIVIEW || k == SHADER_VERSION_SHADOW_PASS_DP) {
-						//none, leave empty
-					} else if (k == SHADER_VERSION_DEPTH_PASS_WITH_MATERIAL) {
-						blend_state = RD::PipelineColorBlendState::create_disabled(5); //writes to normal and roughness in opaque way
-					} else {
-						// ???
 					}
-				}
 
-				RID shader_variant = shader_singleton->shader.version_get_shader(version, k);
-				pipelines[i][j][k].setup(shader_variant, primitive_rd, raster_state, multisample_state, depth_stencil, blend_state, 0, singleton->default_specialization_constants);
+					RID shader_variant = shader_singleton->shader.version_get_shader(version, k);
+					pipelines[i][j][k][l].setup(shader_variant, primitive_rd, raster_state, multisample_state, depth_stencil, blend_state, 0, singleton->default_specialization_constants);
+				}
 			}
 		}
 	}
@@ -757,7 +760,9 @@ void SceneShaderForwardMobile::set_default_specialization_constants(const Vector
 		for (int i = 0; i < ShaderData::CULL_VARIANT_MAX; i++) {
 			for (int j = 0; j < RS::PRIMITIVE_MAX; j++) {
 				for (int k = 0; k < SHADER_VERSION_MAX; k++) {
-					E->self()->pipelines[i][j][k].update_specialization_constants(default_specialization_constants);
+					for (int l = 0; l < PIPELINE_PASS_COUNT; l++) {
+						E->self()->pipelines[i][j][k][l].update_specialization_constants(default_specialization_constants);
+					}
 				}
 			}
 		}

servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.h

@@ -55,6 +55,12 @@ class SceneShaderForwardMobile {
 		SHADER_VERSION_MAX
 	};
 
+	enum PipelinePasses {
+		PIPELINE_PASS_NOT_COLOR_OR_OPAQUE = 0,
+		PIPELINE_PASS_COLOR_TRANSPARENT = 1,
+		PIPELINE_PASS_COUNT = 2,
+	};
+
 	struct ShaderData : public RendererRD::MaterialStorage::ShaderData {
 		enum BlendMode { //used internally
 			BLEND_MODE_MIX,
@@ -99,7 +105,7 @@ class SceneShaderForwardMobile {
 		bool valid = false;
 		RID version;
 		uint64_t vertex_input_mask = 0;
-		PipelineCacheRD pipelines[CULL_VARIANT_MAX][RS::PRIMITIVE_MAX][SHADER_VERSION_MAX];
+		PipelineCacheRD pipelines[CULL_VARIANT_MAX][RS::PRIMITIVE_MAX][SHADER_VERSION_MAX][PIPELINE_PASS_COUNT];
 
 		Vector<ShaderCompiler::GeneratedCode::Texture> texture_uniforms;
 

servers/rendering/renderer_rd/shaders/forward_mobile/scene_forward_mobile.glsl

@@ -765,7 +765,7 @@ void main() {
 	float ao = 1.0;
 	float ao_light_affect = 0.0;
 
-	float alpha = 1.0;
+	float alpha = float((instances.data[draw_call.instance_index].flags >> INSTANCE_FLAGS_FADE_SHIFT) & INSTANCE_FLAGS_FADE_MASK) / float(255.0);
 
 #if defined(TANGENT_USED) || defined(NORMAL_MAP_USED) || defined(LIGHT_ANISOTROPY_USED)
 	vec3 binormal = normalize(binormal_interp);

servers/rendering/renderer_rd/shaders/forward_mobile/scene_forward_mobile_inc.glsl

@@ -43,8 +43,10 @@ layout(set = 0, binding = 2) uniform sampler shadow_sampler;
 #define INSTANCE_FLAGS_MULTIMESH_HAS_COLOR (1 << 14)
 #define INSTANCE_FLAGS_MULTIMESH_HAS_CUSTOM_DATA (1 << 15)
 #define INSTANCE_FLAGS_PARTICLE_TRAIL_SHIFT 16
+#define INSTANCE_FLAGS_FADE_SHIFT 24
 //3 bits of stride
 #define INSTANCE_FLAGS_PARTICLE_TRAIL_MASK 0xFF
+#define INSTANCE_FLAGS_FADE_MASK 0xFF
 
 layout(set = 0, binding = 3, std430) restrict readonly buffer OmniLights {
 	LightData data[];