Android WebVR implementation, Cardboard 0.5.5 SDK

content/browser/vr/android/cardboard/cardboard_vr_device.cc

Index: content/browser/vr/android/cardboard/cardboard_vr_device.cc
diff --git a/content/browser/vr/android/cardboard/cardboard_vr_device.cc b/content/browser/vr/android/cardboard/cardboard_vr_device.cc
new file mode 100644
index 0000000000000000000000000000000000000000..11f8505ff63143ef650b6fd3662b58114a06daeb
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+++ b/content/browser/vr/android/cardboard/cardboard_vr_device.cc
@@ -0,0 +1,188 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/browser/vr/android/cardboard/cardboard_vr_device.h"
+
+#include <math.h>
+#include <algorithm>
+
+#include "base/android/jni_android.h"
+#include "base/android/jni_array.h"
+#include "base/android/jni_string.h"
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "base/time/time.h"
+#include "jni/CardboardVRDevice_jni.h"
+
+using base::android::AttachCurrentThread;
+
+namespace content {
+
+namespace {
+
+// Source:
+// http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/
+VRVector4Ptr MatrixToOrientationQuat(const float m[16]) {
+  VRVector4Ptr out = VRVector4::New();
+  float trace = m[0] + m[5] + m[10];
+  float root;

[jdduke (slow), 2015/07/21 20:36:27]

Hmm, there's some transform->quaternion code in ui/gfx/transform_util.cc, not
sure if it's worth pulling that into a utility routing and re-using? Don't have
a strong preference.

[bajones, 2015/07/21 23:27:30]

Might be worth doing, though I would probably defer to another patch.

+  if (trace > 0.0f) {
+    root = sqrtf(1.0f + trace) * 2.0f;
+    out->x = (m[9] - m[6]) / root;
+    out->y = (m[2] - m[8]) / root;
+    out->z = (m[4] - m[1]) / root;
+    out->w = 0.25f * root;
+  } else if ((m[0] > m[5]) && (m[0] > m[10])) {
+    root = sqrtf(1.0f + m[0] - m[5] - m[10]) * 2.0f;
+    out->x = 0.25f * root;
+    out->y = (m[1] + m[4]) / root;
+    out->z = (m[2] + m[8]) / root;
+    out->w = (m[9] - m[6]) / root;
+  } else if (m[5] > m[10]) {
+    root = sqrtf(1.0f + m[5] - m[0] - m[10]) * 2.0f;
+    out->x = (m[1] + m[4]) / root;
+    out->y = 0.25f * root;
+    out->z = (m[6] + m[9]) / root;
+    out->w = (m[2] - m[8]) / root;
+  } else {
+    root = sqrtf(1.0f + m[10] - m[0] - m[5]) * 2.0f;
+    out->x = (m[2] + m[8]) / root;
+    out->y = (m[6] + m[9]) / root;
+    out->z = 0.25f * root;
+    out->w = (m[4] - m[1]) / root;
+  }
+
+  return out.Pass();
+}
+
+}  // namespace
+
+bool CardboardVRDevice::RegisterCardboardVRDevice(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+CardboardVRDevice::CardboardVRDevice(VRDeviceProvider* provider)
+    : VRDevice(provider), frame_index_(0) {
+  j_cardboard_device_.Reset(Java_CardboardVRDevice_create(
+      AttachCurrentThread(), base::android::GetApplicationContext()));
+}
+
+CardboardVRDevice::~CardboardVRDevice() {
+  Java_CardboardVRDevice_stopTracking(AttachCurrentThread(),
+                                      j_cardboard_device_.obj());
+}
+
+VRDeviceInfoPtr CardboardVRDevice::GetVRDevice() {
+  VRDeviceInfoPtr device = VRDeviceInfo::New();
+
+  JNIEnv* env = AttachCurrentThread();
+
+  ScopedJavaLocalRef<jstring> j_device_name =
+      Java_CardboardVRDevice_getDeviceName(env, j_cardboard_device_.obj());
+  device->deviceName =
+      base::android::ConvertJavaStringToUTF8(env, j_device_name.obj());
+
+  ScopedJavaLocalRef<jfloatArray> j_fov(env, env->NewFloatArray(4));
+  Java_CardboardVRDevice_getFieldOfView(env, j_cardboard_device_.obj(),
+                                        j_fov.obj());
+
+  std::vector<float> fov;
+  base::android::JavaFloatArrayToFloatVector(env, j_fov.obj(), &fov);
+
+  device->hmdInfo = VRHMDInfo::New();
+  VRHMDInfoPtr& hmdInfo = device->hmdInfo;
+
+  hmdInfo->leftEye = VREyeParameters::New();
+  hmdInfo->rightEye = VREyeParameters::New();
+  VREyeParametersPtr& leftEye = hmdInfo->leftEye;

[jdduke (slow), 2015/07/21 20:36:27]

I guess calling this leftEye (instead of left_eye) keeps the style from the
referenced variable, I'm OK with it not sure about our style policy though.

[bajones, 2015/07/21 23:27:30]

Changed it to left_eye/right_eye anyway.

+  VREyeParametersPtr& rightEye = hmdInfo->rightEye;
+
+  leftEye->recommendedFieldOfView = VRFieldOfView::New();
+  leftEye->recommendedFieldOfView->upDegrees = fov[0];
+  leftEye->recommendedFieldOfView->downDegrees = fov[1];
+  leftEye->recommendedFieldOfView->leftDegrees = fov[2];
+  leftEye->recommendedFieldOfView->rightDegrees = fov[3];
+
+  // Cardboard devices always assume a mirrored FOV, so this is just the left
+  // eye FOV with the left and right degrees swapped.
+  rightEye->recommendedFieldOfView = VRFieldOfView::New();
+  rightEye->recommendedFieldOfView->upDegrees = fov[0];
+  rightEye->recommendedFieldOfView->downDegrees = fov[1];
+  rightEye->recommendedFieldOfView->leftDegrees = fov[3];
+  rightEye->recommendedFieldOfView->rightDegrees = fov[2];
+
+  // Cardboard does not support configurable FOV.
+  leftEye->maximumFieldOfView = leftEye->recommendedFieldOfView.Clone();
+  rightEye->maximumFieldOfView = rightEye->recommendedFieldOfView.Clone();
+  leftEye->minimumFieldOfView = leftEye->recommendedFieldOfView.Clone();
+  rightEye->minimumFieldOfView = rightEye->recommendedFieldOfView.Clone();
+
+  float ipd = Java_CardboardVRDevice_getIpd(env, j_cardboard_device_.obj());
+
+  leftEye->eyeTranslation = VRVector3::New();
+  leftEye->eyeTranslation->x = ipd * -0.5f;
+  leftEye->eyeTranslation->y = 0.0f;
+  leftEye->eyeTranslation->z = 0.0f;
+
+  rightEye->eyeTranslation = VRVector3::New();
+  rightEye->eyeTranslation->x = ipd * 0.5f;
+  rightEye->eyeTranslation->y = 0.0f;
+  rightEye->eyeTranslation->z = 0.0f;
+
+  ScopedJavaLocalRef<jintArray> j_screen_size(env, env->NewIntArray(2));
+  Java_CardboardVRDevice_getScreenSize(env, j_cardboard_device_.obj(),
+                                       j_screen_size.obj());
+
+  std::vector<int> screen_size;
+  base::android::JavaIntArrayToIntVector(env, j_screen_size.obj(),
+                                         &screen_size);
+
+  leftEye->renderRect = VRRect::New();

[jdduke (slow), 2015/07/21 20:36:27]

Just confirming, looks like Mojo does some fanciness here so we're not actually
heap allocating?

+  leftEye->renderRect->x = 0;
+  leftEye->renderRect->y = 0;

[jdduke (slow), 2015/07/21 20:36:27]

If the orientation changes (or the window dimensions change for whatever other
reason), do we recreate the device?

[bajones, 2015/07/21 23:27:30]

For the purposes of VR it's assumed that you will always render stereo scenes in
landscape (which is how your phone goes into Cardboard).

+  leftEye->renderRect->width = screen_size[0] / 2.0;
+  leftEye->renderRect->height = screen_size[1];
+
+  rightEye->renderRect = VRRect::New();
+  rightEye->renderRect->x = screen_size[0] / 2.0;
+  rightEye->renderRect->y = 0;
+  rightEye->renderRect->width = screen_size[0] / 2.0;
+  rightEye->renderRect->height = screen_size[1];
+
+  return device.Pass();
+}
+
+VRSensorStatePtr CardboardVRDevice::GetSensorState() {
+  VRSensorStatePtr state = VRSensorState::New();
+
+  state->timestamp = base::Time::Now().ToJsTime();

[jdduke (slow), 2015/07/21 20:36:27]

Hmm, do they really want wallclock time and not system time? (I may have asked
this before =/). For other input events we populate the timestamp with
TimeTicks::Now(), though Blink eventually ignores that and feeds Time::Now() to
the the web-exposed event.

[bajones, 2015/07/21 23:27:30]

This is an area of the WebVR spec that's underdeveloped, as right now the
concept of a timestamp is just whatever the VR SDK most conveniently provides. I
need to tighten that down with the Mozilla folks, but until then this should be
sufficient.

+  state->frameIndex = frame_index_;
+
+  JNIEnv* env = AttachCurrentThread();
+  ScopedJavaLocalRef<jfloatArray> j_head_matrix(env, env->NewFloatArray(16));

[jdduke (slow), 2015/07/21 20:36:27]

Have you considered storing a persistent Java array in this object, and re-using
it? Would save garbage generation each frame.

[bajones, 2015/07/21 23:27:30]

Done

+  Java_CardboardVRDevice_getSensorState(env, j_cardboard_device_.obj(),
+                                        j_head_matrix.obj());
+
+  std::vector<float> head_matrix;
+  base::android::JavaFloatArrayToFloatVector(env, j_head_matrix.obj(),
+                                             &head_matrix);
+
+  state->orientation = MatrixToOrientationQuat(&head_matrix[0]);
+
+  state->position = VRVector3::New();
+  state->position->x = -head_matrix[12];
+  state->position->y = head_matrix[13];
+  state->position->z = head_matrix[14];
+
+  frame_index_++;

[jdduke (slow), 2015/07/21 20:36:27]

Maybe increment this up where it's used?

[bajones, 2015/07/21 23:27:30]

Done

+
+  return state.Pass();
+}
+
+void CardboardVRDevice::ResetSensor() {
+  Java_CardboardVRDevice_resetSensor(AttachCurrentThread(),
+                                     j_cardboard_device_.obj());
+}
+
+}  // namespace content