Fix the controller being locked in place with 6DoF systems

gvr's Arm model apparently does not take into account the user's head position
on 6DoF systems, leaving the arm model "locked" in place near the origin. This
change manually offsets the controller model by the head's position so that the
arm model for the controller stays at a constant relative position to the head.
This yields behavior that matches Google's other first-party VR applications.

Bug: 831610
Change-Id: Id5cf7013c5b671e320304cd78bc80abd11580300
Reviewed-on: https://chromium-review.googlesource.com/1058558
Commit-Queue: Brandon Jones <bajones@chromium.org>
Reviewed-by: Amirhossein Simjour <asimjour@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558833}

chrome/browser/android/vr/vr_controller.cc

@@ -14,7 +14,6 @@
 #include "third_party/blink/public/platform/web_input_event.h"
 #include "third_party/gvr-android-sdk/src/libraries/headers/vr/gvr/capi/include/gvr.h"
 #include "third_party/gvr-android-sdk/src/libraries/headers/vr/gvr/capi/include/gvr_controller.h"
-#include "ui/gfx/transform.h"
 
 namespace vr {
 
@@ -247,14 +246,16 @@ gfx::Quaternion VrController::Orientation() const {
 }
 
 gfx::Point3F VrController::Position() const {
-  gvr::Vec3f position = controller_state_->GetPosition();
-  return gfx::Point3F(position.x, position.y, position.z);
+  const gvr::Vec3f& position = controller_state_->GetPosition();
+  return gfx::Point3F(position.x + head_offset_.x(),
+                      position.y + head_offset_.y(),
+                      position.z + head_offset_.z());
 }
 
 void VrController::GetTransform(gfx::Transform* out) const {
   *out = gfx::Transform(Orientation());
-  gvr::Vec3f position = controller_state_->GetPosition();
-  out->matrix().postTranslate(position.x, position.y, position.z);
+  const gfx::Point3F& position = Position();
+  out->matrix().postTranslate(position.x(), position.y(), position.z());
 }
 
 void VrController::GetRelativePointerTransform(gfx::Transform* out) const {
@@ -314,9 +315,17 @@ bool VrController::IsConnected() {
   return controller_state_->GetConnectionState() == gvr::kControllerConnected;
 }
 
-void VrController::UpdateState(const gvr::Mat4f& head_direction) {
+void VrController::UpdateState(const gfx::Transform& head_pose) {
+  gfx::Transform inv_pose;
+  if (head_pose.GetInverse(&inv_pose)) {
+    head_offset_.SetPoint(0, 0, 0);
+    inv_pose.TransformPoint(&head_offset_);
+  }
+
+  gvr::Mat4f gvr_head_pose;
+  TransformToGvrMat(head_pose, &gvr_head_pose);
   controller_api_->ApplyArmModel(handedness_, gvr::kArmModelBehaviorFollowGaze,
-                                 head_direction);
+                                 gvr_head_pose);
   const int32_t old_status = controller_state_->GetApiStatus();
   const int32_t old_connection_state = controller_state_->GetConnectionState();
   for (int button = 0; button < GVR_CONTROLLER_BUTTON_COUNT; ++button) {

chrome/browser/android/vr/vr_controller.h

@@ -10,6 +10,7 @@
 
 #include "base/macros.h"
 #include "base/time/time.h"
+#include "chrome/browser/android/vr/gvr_util.h"
 #include "chrome/browser/vr/platform_controller.h"
 #include "device/vr/android/gvr/gvr_gamepad_data_provider.h"
 #include "device/vr/public/mojom/vr_service.mojom.h"
@@ -18,6 +19,7 @@
 #include "ui/gfx/geometry/quaternion.h"
 #include "ui/gfx/geometry/vector2d_f.h"
 #include "ui/gfx/geometry/vector3d_f.h"
+#include "ui/gfx/transform.h"
 
 namespace blink {
 class WebGestureEvent;
@@ -54,7 +56,7 @@ class VrController : public PlatformController {
   device::mojom::XRInputSourceStatePtr GetInputSourceState();
 
   // Called once per frame to update controller state.
-  void UpdateState(const gvr::Mat4f& head_direction);
+  void UpdateState(const gfx::Transform& head_pose);
 
   std::unique_ptr<GestureList> DetectGestures();
 
@@ -192,6 +194,9 @@ class VrController : public PlatformController {
   // Displacement of the touch point from the previews to the current touch
   gfx::Vector2dF displacement_;
 
+  // Head offset. Keeps the controller at the user's side with 6DoF headsets.
+  gfx::Point3F head_offset_;
+
   int64_t last_touch_timestamp_ = 0;
   int64_t last_timestamp_nanos_ = 0;
 

chrome/browser/android/vr/vr_shell_gl.cc

@@ -1183,9 +1183,7 @@ void VrShellGl::UpdateViewports() {
 void VrShellGl::UpdateController(const RenderInfo& render_info,
                                  base::TimeTicks current_time) {
   TRACE_EVENT0("gpu", "VrShellGl::UpdateController");
-  gvr::Mat4f gvr_head_pose;
-  TransformToGvrMat(render_info.head_pose, &gvr_head_pose);
-  controller_->UpdateState(gvr_head_pose);
+  controller_->UpdateState(render_info.head_pose);
   gfx::Point3F laser_origin = controller_->GetPointerStart();
 
   device::GvrGamepadData controller_data = controller_->GetGamepadData();