Adding Variable Rate Shading support to Godot

Improve GI renderer and add VRS support
Implement render device has_feature and move subgroup settings to limit_get

doc/classes/ProjectSettings.xml

@@ -1968,6 +1968,12 @@
 			If [code]true[/code], the texture importer will import VRAM-compressed textures using the S3 Texture Compression algorithm. This algorithm is only supported on desktop platforms and consoles.
 			[b]Note:[/b] Changing this setting does [i]not[/i] impact textures that were already imported before. To make this setting apply to textures that were already imported, exit the editor, remove the [code].godot/imported/[/code] folder located inside the project folder then restart the editor (see [member application/config/use_hidden_project_data_directory]).
 		</member>
+		<member name="rendering/vrs/mode" type="int" setter="" getter="" default="0">
+			Set the default Variable Rate Shading (VRS) mode for the main viewport. See [member Viewport.vrs_mode] to change this at runtime, and [enum Viewport.VRSMode] for possible values.
+		</member>
+		<member name="rendering/vrs/texture" type="String" setter="" getter="" default="&quot;&quot;">
+			If [member rendering/vrs/mode] is set to texture, this is the path to default texture loaded as the VRS image.
+		</member>
 		<member name="rendering/vulkan/descriptor_pools/max_descriptors_per_pool" type="int" setter="" getter="" default="64">
 		</member>
 		<member name="rendering/vulkan/rendering/back_end" type="int" setter="" getter="" default="0">

doc/classes/RenderingDevice.xml

@@ -395,7 +395,7 @@
 			<description>
 			</description>
 		</method>
-		<method name="limit_get">
+		<method name="limit_get" qualifiers="const">
 			<return type="int" />
 			<argument index="0" name="limit" type="int" enum="RenderingDevice.Limit" />
 			<description>

doc/classes/RenderingServer.xml

@@ -3357,6 +3357,22 @@
 				If [code]true[/code], the viewport uses augmented or virtual reality technologies. See [XRInterface].
 			</description>
 		</method>
+		<method name="viewport_set_vrs_mode">
+			<return type="void" />
+			<argument index="0" name="viewport" type="RID" />
+			<argument index="1" name="mode" type="int" enum="RenderingServer.ViewportVRSMode" />
+			<description>
+				Sets the Variable Rate Shading (VRS) mode for the viewport. Note, if hardware does not support VRS this property is ignored.
+			</description>
+		</method>
+		<method name="viewport_set_vrs_texture">
+			<return type="void" />
+			<argument index="0" name="viewport" type="RID" />
+			<argument index="1" name="texture" type="RID" />
+			<description>
+				Texture to use when the VRS mode is set to [constant RenderingServer.VIEWPORT_VRS_TEXTURE].
+			</description>
+		</method>
 		<method name="visibility_notifier_create">
 			<return type="RID" />
 			<description>
@@ -4116,6 +4132,18 @@
 		</constant>
 		<constant name="VIEWPORT_DEBUG_DRAW_MOTION_VECTORS" value="25" enum="ViewportDebugDraw">
 		</constant>
+		<constant name="VIEWPORT_VRS_DISABLED" value="0" enum="ViewportVRSMode">
+			VRS is disabled.
+		</constant>
+		<constant name="VIEWPORT_VRS_TEXTURE" value="1" enum="ViewportVRSMode">
+			VRS uses a texture. Note, for stereoscopic use a texture atlas with a texture for each view.
+		</constant>
+		<constant name="VIEWPORT_VRS_XR" value="2" enum="ViewportVRSMode">
+			VRS texture is supplied by the primary [XRInterface].
+		</constant>
+		<constant name="VIEWPORT_VRS_MAX" value="3" enum="ViewportVRSMode">
+			Represents the size of the [enum ViewportVRSMode] enum.
+		</constant>
 		<constant name="SKY_MODE_AUTOMATIC" value="0" enum="SkyMode">
 		</constant>
 		<constant name="SKY_MODE_QUALITY" value="1" enum="SkyMode">

doc/classes/Viewport.xml

@@ -286,6 +286,12 @@
 		<member name="use_xr" type="bool" setter="set_use_xr" getter="is_using_xr" default="false">
 			If [code]true[/code], the viewport will use the primary XR interface to render XR output. When applicable this can result in a stereoscopic image and the resulting render being output to a headset.
 		</member>
+		<member name="vrs_mode" type="int" setter="set_vrs_mode" getter="get_vrs_mode" enum="Viewport.VRSMode" default="0">
+			The Variable Rate Shading (VRS) mode that is used for this viewport. Note, if hardware does not support VRS this property is ignored.
+		</member>
+		<member name="vrs_texture" type="Texture2D" setter="set_vrs_texture" getter="get_vrs_texture">
+			Texture to use when [member vrs_mode] is set to [constant Viewport.VRS_TEXTURE].
+		</member>
 		<member name="world_2d" type="World2D" setter="set_world_2d" getter="get_world_2d">
 			The custom [World2D] which can be used as 2D environment source.
 		</member>
@@ -492,5 +498,17 @@
 		</constant>
 		<constant name="SDF_SCALE_MAX" value="3" enum="SDFScale">
 		</constant>
+		<constant name="VRS_DISABLED" value="0" enum="VRSMode">
+			VRS is disabled.
+		</constant>
+		<constant name="VRS_TEXTURE" value="1" enum="VRSMode">
+			VRS uses a texture. Note, for stereoscopic use a texture atlas with a texture for each view.
+		</constant>
+		<constant name="VRS_XR" value="2" enum="VRSMode">
+			VRS texture is supplied by the primary [XRInterface].
+		</constant>
+		<constant name="VRS_MAX" value="3" enum="VRSMode">
+			Represents the size of the [enum VRSMode] enum.
+		</constant>
 	</constants>
 </class>

doc/classes/XRInterfaceExtension.xml

@@ -106,6 +106,11 @@
 				Returns the number of views this interface requires, 1 for mono, 2 for stereoscopic.
 			</description>
 		</method>
+		<method name="_get_vrs_texture" qualifiers="virtual">
+			<return type="RID" />
+			<description>
+			</description>
+		</method>
 		<method name="_initialize" qualifiers="virtual">
 			<return type="bool" />
 			<description>

drivers/gles3/storage/texture_storage.h

@@ -546,6 +546,16 @@ class TextureStorage : public RendererTextureStorage {
 	void render_target_copy_to_back_buffer(RID p_render_target, const Rect2i &p_region, bool p_gen_mipmaps);
 	void render_target_clear_back_buffer(RID p_render_target, const Rect2i &p_region, const Color &p_color);
 	void render_target_gen_back_buffer_mipmaps(RID p_render_target, const Rect2i &p_region);
+	virtual void render_target_set_vrs_mode(RID p_render_target, RS::ViewportVRSMode p_mode) override{};
+	virtual void render_target_set_vrs_texture(RID p_render_target, RID p_texture) override{};
+
+	void bind_framebuffer(GLuint framebuffer) {
+		glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
+	}
+
+	void bind_framebuffer_system() {
+		glBindFramebuffer(GL_FRAMEBUFFER, GLES3::TextureStorage::system_fbo);
+	}
 
 	String get_framebuffer_error(GLenum p_status);
 };