From 21331b5c42e3bde159e28017c61eeb9bb6b7be7a Mon Sep 17 00:00:00 2001
From: galister <22305755+galister@users.noreply.github.com>
Date: Mon, 16 Sep 2024 05:09:10 +0900
Subject: [PATCH] fps-aware openxr pointer smoothing

---
 src/backend/openxr/input.rs | 9 +++++----
 src/backend/openxr/mod.rs   | 3 +++
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/backend/openxr/input.rs b/src/backend/openxr/input.rs
index b80a467..7f68f6a 100644
--- a/src/backend/openxr/input.rs
+++ b/src/backend/openxr/input.rs
@@ -324,12 +324,13 @@ impl OpenXrHand {
                     transmute::<Vector3f, Vec3>(location.pose.position),
                 )
             };
+            let lerp_factor = (1.0 / (xr.predicted_display_period.as_nanos() / 10_000_000) as f32
+                * session.config.pointer_lerp_factor)
+                .clamp(0.1, 1.0);
             pointer.raw_pose = Affine3A::from_rotation_translation(new_quat, new_pos);
             pointer.pose = Affine3A::from_rotation_translation(
-                cur_quat.lerp(new_quat, session.config.pointer_lerp_factor),
-                cur_pos
-                    .lerp(new_pos.into(), session.config.pointer_lerp_factor)
-                    .into(),
+                cur_quat.lerp(new_quat, lerp_factor),
+                cur_pos.lerp(new_pos.into(), lerp_factor).into(),
             );
         }
 
diff --git a/src/backend/openxr/mod.rs b/src/backend/openxr/mod.rs
index 07e6f93..6b249aa 100644
--- a/src/backend/openxr/mod.rs
+++ b/src/backend/openxr/mod.rs
@@ -48,6 +48,7 @@ struct XrState {
     system: xr::SystemId,
     session: xr::Session<xr::Vulkan>,
     predicted_display_time: xr::Time,
+    predicted_display_period: xr::Duration,
     stage: Arc<xr::Space>,
     view: Arc<xr::Space>,
     stage_offset: Affine3A,
@@ -131,6 +132,7 @@ pub fn openxr_run(running: Arc<AtomicBool>, show_by_default: bool) -> Result<(),
         system,
         session,
         predicted_display_time: xr::Time::from_nanos(0),
+        predicted_display_period: xr::Duration::from_nanos(10_000_000),
         stage: Arc::new(stage),
         view: Arc::new(view),
         stage_offset: Affine3A::IDENTITY,
@@ -231,6 +233,7 @@ pub fn openxr_run(running: Arc<AtomicBool>, show_by_default: bool) -> Result<(),
         frame_stream.begin()?;
 
         xr_state.predicted_display_time = xr_frame_state.predicted_display_time;
+        xr_state.predicted_display_period = xr_frame_state.predicted_display_period;
 
         if !xr_frame_state.should_render {
             frame_stream.end(