Added Backend.OpenXR.EyesSampleTime

Examples/StereoKitTest/Demos/DemoEyes.cs

@@ -1,4 +1,5 @@
-using StereoKit;
+using System;
+using StereoKit;
 using System.Collections.Generic;
 
 class DemoEyes : ITest
@@ -11,13 +12,23 @@ class DemoEyes : ITest
 	List<LinePoint> points = new List<LinePoint>();
 	Vec3 previous;
 
-	public void Initialize() { }
+	long lastEyesSampleTime;
+	DateTime demoStartTime;
+	int uniqueSamplesCount;
+
+	public void Initialize()
+	{
+		demoStartTime = DateTime.UtcNow;
+		uniqueSamplesCount = 0;
+		lastEyesSampleTime = -1;
+	}
 	public void Shutdown  () { }
 
 	public void Update()
 	{
 		Plane plane = new Plane(new Vec3(0.5f,0,-0.5f), V.XYZ(-0.5f,0,0.5f));
-		Mesh.Quad.Draw(Material.Default, Matrix.TRS(new Vec3(0.54f, 0, -0.468f), Quat.LookDir(plane.normal), 0.5f));
+		Matrix quadPose = Matrix.TRS(new Vec3(0.54f, 0, -0.468f), Quat.LookDir(plane.normal), 0.5f);
+		Mesh.Quad.Draw(Material.Default, quadPose);
 		if (Input.Eyes.Ray.Intersect(plane, out Vec3 at))
 		{
 			Color stateColor = Input.EyesTracked.IsActive() 
@@ -46,5 +57,17 @@ public void Update()
 
 		Text.Add(title, titlePose);
 		Text.Add(description, descPose, V.XY(0.4f, 0), TextFit.Wrap, TextAlign.TopCenter, TextAlign.TopLeft);
+
+		if (Backend.XRType == BackendXRType.OpenXR)
+		{
+			if (Backend.OpenXR.EyesSampleTime != lastEyesSampleTime)
+            {
+				lastEyesSampleTime = Backend.OpenXR.EyesSampleTime;
+				uniqueSamplesCount++;
+            }
+
+			double sampleFrequency = uniqueSamplesCount / (DateTime.UtcNow - demoStartTime).TotalSeconds;
+			Text.Add($"Eye tracker sampling frequency: {sampleFrequency:0.#} Hz", Matrix.T(V.XYZ(0, -0.55f, -0.1f)) * quadPose);
+		}
 	}
 }

Examples/StereoKitTest/Demos/DemoQRCode.cs

@@ -6,7 +6,7 @@
 /// :CodeDoc: Guides 4 Using QR Codes
 /// # Using QR Codes
 /// 
-/// QR codes are a super fast and easy way to to locate an object,
+/// QR codes are a super fast and easy way to locate an object,
 /// provide information from the environment, or `localize` two
 /// devices to the same coordinate space! HoloLens 2 and WMR headsets
 /// have a really convenient way to grab and use this data. They can use

StereoKit/Native/NativeAPI.cs

@@ -486,6 +486,7 @@ internal static class NativeAPI
 		[DllImport(dll, CharSet = cSet, CallingConvention = call)] public static extern ulong         backend_openxr_get_session ();
 		[DllImport(dll, CharSet = cSet, CallingConvention = call)] public static extern ulong         backend_openxr_get_space   ();
 		[DllImport(dll, CharSet = cSet, CallingConvention = call)] public static extern long          backend_openxr_get_time    ();
+		[DllImport(dll, CharSet = cSet, CallingConvention = call)] public static extern long          backend_openxr_get_eyes_sample_time();
 		[DllImport(dll, CharSet = cSet, CallingConvention = call)] public static extern IntPtr        backend_openxr_get_function(string function_name);
 		[DllImport(dll, CharSet = cSet, CallingConvention = call)] public static extern int           backend_openxr_ext_enabled (string extension_name);
 		[DllImport(dll, CharSet = cSet, CallingConvention = call)] public static extern void          backend_openxr_ext_request (string extension_name);

StereoKit/Systems/Backend.cs

@@ -55,6 +55,10 @@ public static class OpenXR
 			/// frame, and is available after SK.Initialize.</summary>
 			public static long Time => NativeAPI.backend_openxr_get_time();
 
+			/// <summary>Type: XrTime. This is the OpenXR time of the eye tracker
+			/// sample associated with the current value of <see cref="Input.Eyes"/>.</summary>
+			public static long EyesSampleTime => NativeAPI.backend_openxr_get_eyes_sample_time();
+
 			/// <summary>This tells if an OpenXR extension has been requested
 			/// and successfully loaded by the runtime. This MUST only be
 			/// called after SK.Initialize.</summary>

StereoKitC/stereokit.h

@@ -1897,6 +1897,7 @@ SK_API openxr_handle_t   backend_openxr_get_instance();
 SK_API openxr_handle_t   backend_openxr_get_session ();
 SK_API openxr_handle_t   backend_openxr_get_space   ();
 SK_API int64_t           backend_openxr_get_time    ();
+SK_API int64_t           backend_openxr_get_eyes_sample_time();
 SK_API void             *backend_openxr_get_function(const char *function_name);
 SK_API bool32_t          backend_openxr_ext_enabled (const char *extension_name);
 SK_API void              backend_openxr_ext_request (const char *extension_name);

StereoKitC/systems/platform/openxr.cpp

@@ -56,6 +56,7 @@ XrSpace        xr_stage_space   = {};
 XrSpace        xr_head_space    = {};
 XrSystemId     xr_system_id     = XR_NULL_SYSTEM_ID;
 XrTime         xr_time          = 0;
+XrTime         xr_eyes_sample_time = 0;
 
 array_t<const char*> xr_exts_user   = {};
 array_t<uint64_t>    xr_exts_loaded = {};
@@ -701,6 +702,23 @@ bool32_t openxr_get_space(XrSpace space, pose_t *out_pose, XrTime time) {
 
 ///////////////////////////////////////////
 
+bool32_t openxr_get_gaze_space(pose_t* out_pose, XrTime &out_gaze_sample_time, XrTime time) {
+	if (time == 0) time = xr_time;
+
+	XrEyeGazeSampleTimeEXT gaze_sample_time = { XR_TYPE_EYE_GAZE_SAMPLE_TIME_EXT };
+	XrSpaceLocation space_location = { XR_TYPE_SPACE_LOCATION, &gaze_sample_time };
+	XrResult        res = xrLocateSpace(xr_gaze_space, xr_app_space, time, &space_location);
+	if (XR_UNQUALIFIED_SUCCESS(res) && openxr_loc_valid(space_location)) {
+		memcpy(&out_pose->position, &space_location.pose.position, sizeof(vec3));
+		memcpy(&out_pose->orientation, &space_location.pose.orientation, sizeof(quat));
+		out_gaze_sample_time = gaze_sample_time.time;
+		return true;
+	}
+	return false;
+}
+
+///////////////////////////////////////////
+
 pose_t world_from_spatial_graph(uint8_t spatial_graph_node_id[16], bool32_t dynamic, int64_t qpc_time) {
 	if (!xr_session) {
 		log_warn("No OpenXR session available for converting spatial graph nodes!");
@@ -897,6 +915,14 @@ int64_t backend_openxr_get_time() {
 
 ///////////////////////////////////////////
 
+int64_t backend_openxr_get_eyes_sample_time() {
+	if (backend_xr_get_type() != backend_xr_type_openxr)
+		log_err("backend_openxr_ functions only work when OpenXR is the backend!");
+	return xr_eyes_sample_time;
+}
+
+///////////////////////////////////////////
+
 void *backend_openxr_get_function(const char *function_name) {
 	if (backend_xr_get_type() != backend_xr_type_openxr)
 		log_err("backend_openxr_ functions only work when OpenXR is the backend!");

StereoKitC/systems/platform/openxr.h

@@ -138,11 +138,13 @@ void openxr_poll_actions  ();
 
 void       *openxr_get_luid ();
 bool32_t    openxr_get_space(XrSpace space, pose_t *out_pose, XrTime time = 0);
+bool32_t    openxr_get_gaze_space(pose_t* out_pose, XrTime& out_gaze_sample_time, XrTime time = 0);
 const char* openxr_string   (XrResult result);
 
 extern XrSpace    xrc_space_grip[2];
 extern XrSpace    xr_app_space;
 extern XrSpace    xr_head_space;
+extern XrSpace    xr_gaze_space;
 extern XrInstance xr_instance;
 extern XrSession  xr_session;
 extern XrSessionState xr_session_state;
@@ -153,6 +155,7 @@ extern bool       xr_has_depth_lsr;
 extern bool       xr_has_bounds;
 extern bool       xr_has_single_pass;
 extern XrTime     xr_time;
+extern XrTime     xr_eyes_sample_time;
 extern vec2       xr_bounds_size;
 extern pose_t     xr_bounds_pose;
 extern pose_t     xr_bounds_pose_local;

StereoKitC/systems/platform/openxr_input.cpp

@@ -598,7 +598,7 @@ void oxri_update_poses() {
 		action_info.action = xrc_action_eyes;
 		xrGetActionStatePose(xr_session, &action_info, &action_pose);
 
-		if (action_pose.isActive && openxr_get_space(xr_gaze_space, &input_eyes_pose_local)) {
+		if (action_pose.isActive && openxr_get_gaze_space(&input_eyes_pose_local, xr_eyes_sample_time)) {
 			input_eyes_pose_world.position    = root   * input_eyes_pose_local.position;
 			input_eyes_pose_world.orientation = root_q * input_eyes_pose_local.orientation;