3 files changed, 73 insertions, 4 deletions

diff --git a/servers/arvr_server.cpp b/servers/arvr_server.cpp
index 8620b182df..f9d402fe7b 100644
--- a/servers/arvr_server.cpp
+++ b/servers/arvr_server.cpp
@@ -44,6 +44,7 @@ void ARVRServer::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_world_scale"), &ARVRServer::set_world_scale);
 	ClassDB::bind_method(D_METHOD("get_reference_frame"), &ARVRServer::get_reference_frame);
 	ClassDB::bind_method(D_METHOD("center_on_hmd", "rotation_mode", "keep_height"), &ARVRServer::center_on_hmd);
+	ClassDB::bind_method(D_METHOD("get_hmd_transform"), &ARVRServer::get_hmd_transform);
 
 	ADD_PROPERTY(PropertyInfo(Variant::REAL, "world_scale"), "set_world_scale", "get_world_scale");
 
@@ -54,8 +55,13 @@ void ARVRServer::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("get_tracker_count"), &ARVRServer::get_tracker_count);
 	ClassDB::bind_method(D_METHOD("get_tracker", "idx"), &ARVRServer::get_tracker);
 
+	ClassDB::bind_method(D_METHOD("get_primary_interface"), &ARVRServer::get_primary_interface);
 	ClassDB::bind_method(D_METHOD("set_primary_interface", "interface"), &ARVRServer::set_primary_interface);
 
+	ClassDB::bind_method(D_METHOD("get_last_process_usec"), &ARVRServer::get_last_process_usec);
+	ClassDB::bind_method(D_METHOD("get_last_commit_usec"), &ARVRServer::get_last_commit_usec);
+	ClassDB::bind_method(D_METHOD("get_last_frame_usec"), &ARVRServer::get_last_frame_usec);
+
 	BIND_ENUM_CONSTANT(TRACKER_CONTROLLER);
 	BIND_ENUM_CONSTANT(TRACKER_BASESTATION);
 	BIND_ENUM_CONSTANT(TRACKER_ANCHOR);
@@ -132,6 +138,14 @@ void ARVRServer::center_on_hmd(RotationMode p_rotation_mode, bool p_keep_height)
 	};
 };
 
+Transform ARVRServer::get_hmd_transform() {
+	Transform hmd_transform;
+	if (primary_interface != NULL) {
+		hmd_transform = primary_interface->get_transform_for_eye(ARVRInterface::EYE_MONO, hmd_transform);
+	};
+	return hmd_transform;
+};
+
 void ARVRServer::add_interface(const Ref<ARVRInterface> &p_interface) {
 	ERR_FAIL_COND(p_interface.is_null());
 
@@ -314,6 +328,42 @@ void ARVRServer::clear_primary_interface_if(const Ref<ARVRInterface> &p_primary_
 	};
 };
 
+uint64_t ARVRServer::get_last_process_usec() {
+	return last_process_usec;
+};
+
+uint64_t ARVRServer::get_last_commit_usec() {
+	return last_commit_usec;
+};
+
+uint64_t ARVRServer::get_last_frame_usec() {
+	return last_frame_usec;
+};
+
+void ARVRServer::_process() {
+	/* called from visual_server_viewport.draw_viewports right before we start drawing our viewports */
+
+	/* mark for our frame timing */
+	last_process_usec = OS::get_singleton()->get_ticks_usec();
+
+	/* process all active interfaces */
+	for (int i = 0; i < interfaces.size(); i++) {
+		if (!interfaces[i].is_valid()) {
+			// ignore, not a valid reference
+		} else if (interfaces[i]->is_initialized()) {
+			interfaces[i]->process();
+		};
+	};
+};
+
+void ARVRServer::_mark_commit() {
+	/* time this */
+	last_commit_usec = OS::get_singleton()->get_ticks_usec();
+
+	/* now store our difference as we may overwrite last_process_usec before this is accessed */
+	last_frame_usec = last_commit_usec - last_process_usec;
+};
+
 ARVRServer::ARVRServer() {
 	singleton = this;
 	world_scale = 1.0;
diff --git a/servers/arvr_server.h b/servers/arvr_server.h
index 63b7edc73b..1f4d84fe19 100644
--- a/servers/arvr_server.h
+++ b/servers/arvr_server.h
@@ -31,6 +31,7 @@
 #ifndef ARVR_SERVER_H
 #define ARVR_SERVER_H
 
+#include "os/os.h"
 #include "os/thread_safe.h"
 #include "reference.h"
 #include "rid.h"
@@ -84,6 +85,10 @@ private:
 	Transform world_origin; /* our world origin point, maps a location in our virtual world to the origin point in our real world tracking volume */
 	Transform reference_frame; /* our reference frame */
 
+	uint64_t last_process_usec; /* for frame timing, usec when we did our processing */
+	uint64_t last_commit_usec; /* for frame timing, usec when we finished committing both eyes */
+	uint64_t last_frame_usec; /* time it took between process and commiting, we should probably average this over the last x frames */
+
 protected:
 	static ARVRServer *singleton;
 
@@ -134,6 +139,11 @@ public:
 	void center_on_hmd(RotationMode p_rotation_mode, bool p_keep_height);
 
 	/*
+		get_hmd_transform gets our hmd transform (centered between eyes) with most up to date tracking, relative to the origin
+	*/
+	Transform get_hmd_transform();
+
+	/*
 		Interfaces are objects that 'glue' Godot to an AR or VR SDK such as the Oculus SDK, OpenVR, OpenHMD, etc.
 	*/
 	void add_interface(const Ref<ARVRInterface> &p_interface);
@@ -163,6 +173,13 @@ public:
 	ARVRPositionalTracker *get_tracker(int p_index) const;
 	ARVRPositionalTracker *find_by_type_and_id(TrackerType p_tracker_type, int p_tracker_id) const;
 
+	uint64_t get_last_process_usec();
+	uint64_t get_last_commit_usec();
+	uint64_t get_last_frame_usec();
+
+	void _process();
+	void _mark_commit();
+
 	ARVRServer();
 	~ARVRServer();
 };
diff --git a/servers/visual/visual_server_viewport.cpp b/servers/visual/visual_server_viewport.cpp
index 3eb8953c1f..83e05f6f25 100644
--- a/servers/visual/visual_server_viewport.cpp
+++ b/servers/visual/visual_server_viewport.cpp
@@ -239,10 +239,9 @@ void VisualServerViewport::_draw_viewport(Viewport *p_viewport, ARVRInterface::E
 void VisualServerViewport::draw_viewports() {
 	// get our arvr interface in case we need it
 	Ref<ARVRInterface> arvr_interface = ARVRServer::get_singleton()->get_primary_interface();
-	if (arvr_interface.is_valid()) {
-		// update our positioning information as late as possible...
-		arvr_interface->process();
-	}
+
+	// process all our active interfaces
+	ARVRServer::get_singleton()->_process();
 
 	clear_color = GLOBAL_GET("rendering/environment/default_clear_color");
 
@@ -286,6 +285,9 @@ void VisualServerViewport::draw_viewports() {
 				_draw_viewport(vp, ARVRInterface::EYE_RIGHT);
 				arvr_interface->commit_for_eye(ARVRInterface::EYE_RIGHT, vp->render_target, vp->viewport_to_screen_rect);
 			}
+
+			// and for our frame timing, mark when we've finished commiting our eyes
+			ARVRServer::get_singleton()->_mark_commit();
 		} else {
 			VSG::rasterizer->set_current_render_target(vp->render_target);