Incorporate 15 degree laser beam angle on pointer.

chrome/browser/android/vr_shell/vr_shell.cc

Index: chrome/browser/android/vr_shell/vr_shell.cc
diff --git a/chrome/browser/android/vr_shell/vr_shell.cc b/chrome/browser/android/vr_shell/vr_shell.cc
index b8e905c54b031b67f5dfcf52816416821b05361c..b0b6b26c9ceefdae79281ec182dc4b45ff3cabe5 100644
--- a/chrome/browser/android/vr_shell/vr_shell.cc
+++ b/chrome/browser/android/vr_shell/vr_shell.cc
@@ -49,11 +49,8 @@ static constexpr float kReticleHeight = 0.025f;
 
 static constexpr float kLaserWidth = 0.01f;
 
-// The neutral direction is fixed in world space, this is the
-// reference angle pointing forward towards the horizon when the
-// controller orientation is reset. This should match the yaw angle
-// where the main screen is placed.
-static constexpr gvr::Vec3f kNeutralPose = {0.0f, 0.0f, -1.0f};
+// Angle the beam down from the controller axis, for wrist comfort.

[mthiesse, 2016/10/05 23:29:10]

nit: s/Angle/Angle (radians)/ ?

[cjgrant, 2016/10/06 15:07:51]

Done.

+static constexpr float kLaserAngle = 0.26f;

[mthiesse, 2016/10/05 23:29:10]

Daydream calls this kErgoAngleOffset, we should probably follow suit for
clarity?

[cjgrant, 2016/10/06 15:07:51]

Done.

 
 static constexpr gvr::Vec3f kOrigin = {0.0f, 0.0f, 0.0f};
 
@@ -239,16 +236,19 @@ void VrShell::UpdateController(const gvr::Vec3f& forward_vector) {
   }
 
   WebInputEvent::Type original_type = gesture->type;
+  gvr::Vec3f beam;

[mthiesse, 2016/10/05 23:29:10]

'beam' here is slightly confusing. Maybe ergo_neutral_pose?

[cjgrant, 2016/10/06 15:07:51]

Done.

   if (!controller_->IsConnected()) {
     // No controller detected, set up a gaze cursor that tracks the
     // forward direction.
+    beam = {0.0f, 0.0f, -1.0f};
     controller_quat_ = GetRotationFromZAxis(forward_vector);
   } else {
+    beam = {0.0f, -sin(kLaserAngle), -cos(kLaserAngle)};
     controller_quat_ = controller_->Orientation();
   }
 
   gvr::Mat4f mat = QuatToMatrix(controller_quat_);
-  gvr::Vec3f forward = MatrixVectorMul(mat, kNeutralPose);
+  gvr::Vec3f forward = MatrixVectorMul(mat, beam);
   gvr::Vec3f origin = kHandPosition;
 
   target_element_ = nullptr;
@@ -523,14 +523,31 @@ void VrShell::DrawCursor(const gvr::Mat4f& render_matrix) {
   auto m = QuatToMatrix(q);
   mat = MatrixMul(m, mat);
 
-  // Orient according to controller position.
-  mat = MatrixMul(QuatToMatrix(controller_quat_), mat);
-
-  // Move the beam origin to the hand.
-  TranslateM(mat, mat, kHandPosition.x, kHandPosition.y, kHandPosition.z);
-
-  transform = MatrixMul(render_matrix, mat);
-  vr_shell_renderer_->GetLaserRenderer()->Draw(transform);
+  const gvr::Vec3f beam_direction = {
+    target_point_.x - kHandPosition.x,
+    target_point_.y - kHandPosition.y,
+    target_point_.z - kHandPosition.z
+  };
+  auto beam_quat = GetRotationFromZAxis(beam_direction);
+
+  // Render multiple faces to make the laser appear cylindrical.
+  const auto faces = 4;

[mthiesse, 2016/10/05 23:29:10]

Prefer types for simple types? 'int' is even shorter than 'auto' :P

[cjgrant, 2016/10/06 15:07:51]

Done.

+  for (int i = 0; i < faces; i++) {
+    // Rotate around Z.
+    float angle = M_PI * 2 * i / faces;
+    auto rot = QuatFromAxisAngle({0.0f, 0.0f, 1.0f}, angle);

[mthiesse, 2016/10/05 23:29:10]

I would prefer types here for clarity, but I'd listen to arguments to the
contrary.

[cjgrant, 2016/10/06 15:07:51]

Done.  No argument.  :)

+    auto face_mat = MatrixMul(QuatToMatrix(rot), mat);
+
+    // Orient according to target direction.
+    face_mat = MatrixMul(QuatToMatrix(beam_quat), face_mat);
+
+    // Move the beam origin to the hand.
+    TranslateM(face_mat, face_mat, kHandPosition.x, kHandPosition.y,
+               kHandPosition.z);
+
+    transform = MatrixMul(render_matrix, face_mat);
+    vr_shell_renderer_->GetLaserRenderer()->Draw(transform);
+  }
 }
 
 void VrShell::DrawWebVr() {