WebVR: add angular velocity estimate to pose

chrome/browser/android/vr_shell/vr_shell_gl.cc

Index: chrome/browser/android/vr_shell/vr_shell_gl.cc
diff --git a/chrome/browser/android/vr_shell/vr_shell_gl.cc b/chrome/browser/android/vr_shell/vr_shell_gl.cc
index 587c233fa5b55a6d3916c2c89d31676ba5df54af..a50bbb245ac956d94b941649c95ff65b53eadc5f 100644
--- a/chrome/browser/android/vr_shell/vr_shell_gl.cc
+++ b/chrome/browser/android/vr_shell/vr_shell_gl.cc
@@ -35,10 +35,6 @@
 namespace vr_shell {
 
 namespace {
-// TODO(mthiesse): If gvr::PlatformInfo().GetPosePredictionTime() is ever
-// exposed, use that instead (it defaults to 50ms on most platforms).
-static constexpr int64_t kPredictionTimeWithoutVsyncNanos = 50000000;
-
 static constexpr float kZNear = 0.1f;
 static constexpr float kZFar = 1000.0f;
 
@@ -807,7 +803,8 @@ void VrShellGl::DrawFrame(int16_t frame_index) {
     head_pose = webvr_head_pose_[frame_index % kPoseRingBufferSize];
   } else {
     gvr::ClockTimePoint target_time = gvr::GvrApi::GetTimePointNow();
-    target_time.monotonic_system_time_nanos += kPredictionTimeWithoutVsyncNanos;
+    target_time.monotonic_system_time_nanos +=
+        VrShell::kPredictionTimeWithoutVsyncNanos;
     head_pose = gvr_api_->GetHeadSpaceFromStartSpaceRotation(target_time);
   }
 
@@ -1264,15 +1261,23 @@ void VrShellGl::SendVSync(base::TimeDelta time,
   TRACE_EVENT1("input", "VrShellGl::SendVSync", "frame", frame_index);
 
   gvr::ClockTimePoint target_time = gvr::GvrApi::GetTimePointNow();
-  target_time.monotonic_system_time_nanos += kPredictionTimeWithoutVsyncNanos;
+  target_time.monotonic_system_time_nanos +=
+      VrShell::kPredictionTimeWithoutVsyncNanos;

[mthiesse, 2017/04/05 18:43:18]

Instead of moving this constant to the header, and using it in 4 different
spots, can we add a static function that gets the predicted head pose with neck
model?

(Will be easier after my refactor in the cq lands
(https://codereview.chromium.org/2787873002/))

[mthiesse, 2017/04/05 18:57:00]

Actually, don't worry about this for your CL. I'll do some refactoring in a
followup.

[klausw, 2017/04/05 22:38:22]

Done, now there's just one place that applies the neck model.

 
   gvr::Mat4f head_mat =
       gvr_api_->GetHeadSpaceFromStartSpaceRotation(target_time);
   head_mat = gvr_api_->ApplyNeckModel(head_mat, 1.0f);
 
+  target_time.monotonic_system_time_nanos +=
+      VrShell::kAngularVelocityEpsilonNanos;
+  gvr::Mat4f head_mat_2 =
+      gvr_api_->GetHeadSpaceFromStartSpaceRotation(target_time);
+
   webvr_head_pose_[frame_index % kPoseRingBufferSize] = head_mat;
 
-  callback.Run(VrShell::VRPosePtrFromGvrPose(head_mat), time, frame_index,
+  callback.Run(VrShell::VRPosePtrFromGvrPose(
+                   head_mat, head_mat_2, VrShell::kAngularVelocityEpsilonNanos),
+               time, frame_index,
                device::mojom::VRVSyncProvider::Status::SUCCESS);
 }