XR: Allow locking the camera to the `XROrigin3D` for benchmarking or automated testing

doc/classes/XRServer.xml

@@ -111,6 +111,10 @@
 		</method>
 	</methods>
 	<members>
+		<member name="camera_locked_to_origin" type="bool" setter="set_camera_locked_to_origin" getter="is_camera_locked_to_origin" default="false">
+			If set to [code]true[/code], the scene will be rendered as if the camera is locked to the [XROrigin3D].
+			[b]Note:[/b] This doesn't provide a very comfortable experience for users. This setting exists for doing benchmarking or automated testing, where you want to control what is rendered via code.
+		</member>
 		<member name="primary_interface" type="XRInterface" setter="set_primary_interface" getter="get_primary_interface">
 			The primary [XRInterface] currently bound to the [XRServer].
 		</member>

servers/rendering/renderer_scene_cull.cpp

@@ -2773,6 +2773,8 @@ void RendererSceneCull::render_camera(const Ref<RenderSceneBuffers> &p_render_bu
 
 		camera_data.set_camera(transform, projection, is_orthogonal, is_frustum, vaspect, jitter, taa_frame_count, camera->visible_layers);
 	} else {
+		XRServer *xr_server = XRServer::get_singleton();
+
 		// Setup our camera for our XR interface.
 		// We can support multiple views here each with their own camera
 		Transform3D transforms[RendererSceneRender::MAX_RENDER_VIEWS];
@@ -2783,7 +2785,7 @@ void RendererSceneCull::render_camera(const Ref<RenderSceneBuffers> &p_render_bu
 
 		float aspect = p_viewport_size.width / (float)p_viewport_size.height;
 
-		Transform3D world_origin = XRServer::get_singleton()->get_world_origin();
+		Transform3D world_origin = xr_server->get_world_origin();
 
 		// We ignore our camera position, it will have been positioned with a slightly old tracking position.
 		// Instead we take our origin point and have our XR interface add fresh tracking data! Whoohoo!
@@ -2792,6 +2794,14 @@ void RendererSceneCull::render_camera(const Ref<RenderSceneBuffers> &p_render_bu
 			projections[v] = p_xr_interface->get_projection_for_view(v, aspect, camera->znear, camera->zfar);
 		}
 
+		// If requested, we move the views to be rendered as if the HMD is at the XROrigin.
+		if (unlikely(xr_server->is_camera_locked_to_origin())) {
+			Transform3D camera_reset = p_xr_interface->get_camera_transform().affine_inverse() * xr_server->get_reference_frame().affine_inverse();
+			for (uint32_t v = 0; v < view_count; v++) {
+				transforms[v] *= camera_reset;
+			}
+		}
+
 		if (view_count == 1) {
 			camera_data.set_camera(transforms[0], projections[0], false, false, camera->vaspect, jitter, p_jitter_phase_count, camera->visible_layers);
 		} else if (view_count == 2) {

servers/xr_server.cpp

@@ -62,9 +62,12 @@ void XRServer::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("clear_reference_frame"), &XRServer::clear_reference_frame);
 	ClassDB::bind_method(D_METHOD("center_on_hmd", "rotation_mode", "keep_height"), &XRServer::center_on_hmd);
 	ClassDB::bind_method(D_METHOD("get_hmd_transform"), &XRServer::get_hmd_transform);
+	ClassDB::bind_method(D_METHOD("set_camera_locked_to_origin", "enabled"), &XRServer::set_camera_locked_to_origin);
+	ClassDB::bind_method(D_METHOD("is_camera_locked_to_origin"), &XRServer::is_camera_locked_to_origin);
 
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "world_scale"), "set_world_scale", "get_world_scale");
 	ADD_PROPERTY(PropertyInfo(Variant::VECTOR3, "world_origin"), "set_world_origin", "get_world_origin");
+	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "camera_locked_to_origin"), "set_camera_locked_to_origin", "is_camera_locked_to_origin");
 
 	ClassDB::bind_method(D_METHOD("add_interface", "interface"), &XRServer::add_interface);
 	ClassDB::bind_method(D_METHOD("get_interface_count"), &XRServer::get_interface_count);
@@ -241,6 +244,10 @@ Transform3D XRServer::get_hmd_transform() {
 	return hmd_transform;
 }
 
+void XRServer::set_camera_locked_to_origin(bool p_enable) {
+	camera_locked_to_origin = p_enable;
+}
+
 void XRServer::add_interface(const Ref<XRInterface> &p_interface) {
 	ERR_FAIL_COND(p_interface.is_null());
 

servers/xr_server.h

@@ -96,6 +96,7 @@ private:
 	double world_scale = 1.0; /* scale by which we multiply our tracker positions */
 	Transform3D world_origin; /* our world origin point, maps a location in our virtual world to the origin point in our real world tracking volume */
 	Transform3D reference_frame; /* our reference frame */
+	bool camera_locked_to_origin = false;
 
 	// As we may be updating our main state for our next frame while we're still rendering our previous frame,
 	// we need to keep copies around.
@@ -198,6 +199,9 @@ public:
 	*/
 	Transform3D get_hmd_transform();
 
+	void set_camera_locked_to_origin(bool p_enable);
+	inline bool is_camera_locked_to_origin() const { return camera_locked_to_origin; }
+
 	/*
 		Interfaces are objects that 'glue' Godot to an AR or VR SDK such as the Oculus SDK, OpenVR, OpenHMD, etc.
 	*/