samples/ndk-treasurehunt/src/main/jni/treasure_hunt_renderer.cc

/* Copyright 2017 Google Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "treasure_hunt_renderer.h"  // NOLINT
#include "treasure_hunt_shaders.h"  // NOLINT

#include <android/log.h>
#include <assert.h>
#include <stdlib.h>
#include <cmath>
#include <random>

#include "vr/gvr/capi/include/gvr_version.h"

#define LOG_TAG "TreasureHuntCPP"
#define LOGW(...) __android_log_print(ANDROID_LOG_WARN, LOG_TAG, __VA_ARGS__)
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)
#define CHECK(condition)                                                   \
  if (!(condition)) {                                                      \
    LOGE("*** CHECK FAILED at %s:%d: %s", __FILE__, __LINE__, #condition); \
    abort();                                                               \
  }

namespace {
static const float kZNear = 0.01f;
static const float kZFar = 10.0f;
static const float kNeckModelFactor = 1.0f;

// For now, to avoid writing a raycasting system, put the reticle closer than
// any objects.
static const float kMinCubeDistance = 3.5f;
static const float kMaxCubeDistance = 7.0f;
static const float kReticleDistance = 2.0f;

// Depth of the ground plane, in meters. If this (and other distances)
// are too far, 6DOF tracking will have no visible effect.
static const float kDefaultFloorHeight = -2.0f;

static const int kCoordsPerVertex = 3;

static const uint64_t kPredictionTimeWithoutVsyncNanos = 50000000;

// Angle threshold for determining whether the controller is pointing at the
// object.
static const float kAngleLimit = 0.2f;

// Sound file in APK assets.
static const char* kObjectSoundFile = "cube_sound.wav";
static const char* kSuccessSoundFile = "success.wav";

// Convert a GVR matrix to an array of floats suitable for passing to OpenGL.
static std::array<float, 16> MatrixToGLArray(const gvr::Mat4f& matrix) {
  // Note that this performs a *transpose* to a column-major matrix array, as
  // expected by GL.
  std::array<float, 16> result;
  for (int i = 0; i < 4; ++i) {
    for (int j = 0; j < 4; ++j) {
      result[j * 4 + i] = matrix.m[i][j];
    }
  }
  return result;
}

// Flatten a pair of mat4's into an array of 32 floats, useful when feeding
// uniform values to OpenGL for multiview.
static std::array<float, 32> MatrixPairToGLArray(const gvr::Mat4f matrix[]) {
  std::array<float, 32> result;
  for (int i = 0; i < 4; ++i) {
    for (int j = 0; j < 4; ++j) {
      result[j * 4 + i] = matrix[0].m[i][j];
      result[16 + j * 4 + i] = matrix[1].m[i][j];
    }
  }
  return result;
}

// Flatten a pair of vec3's into an array of 6 floats, useful when feeding
// uniform values to OpenGL for multiview.
static std::array<float, 6> VectorPairToGLArray(
    const std::array<float, 3> vec[]) {
  std::array<float, 6> result;
  for (int k = 0; k < 3; ++k) {
    result[k] = vec[0][k];
    result[k + 3] = vec[1][k];
  }
  return result;
}

// Multiply a vector by a matrix.
static std::array<float, 4> MatrixVectorMul(const gvr::Mat4f& matrix,
                                            const std::array<float, 4>& vec) {
  std::array<float, 4> result;
  for (int i = 0; i < 4; ++i) {
    result[i] = 0;
    for (int k = 0; k < 4; ++k) {
      result[i] += matrix.m[i][k] * vec[k];
    }
  }
  return result;
}

// Multiply two matrices.
static gvr::Mat4f MatrixMul(const gvr::Mat4f& matrix1,
                            const gvr::Mat4f& matrix2) {
  gvr::Mat4f result;
  for (int i = 0; i < 4; ++i) {
    for (int j = 0; j < 4; ++j) {
      result.m[i][j] = 0.0f;
      for (int k = 0; k < 4; ++k) {
        result.m[i][j] += matrix1.m[i][k] * matrix2.m[k][j];
      }
    }
  }
  return result;
}

// Drop the last element of a vector.
static std::array<float, 3> Vec4ToVec3(const std::array<float, 4>& vec) {
  return {vec[0], vec[1], vec[2]};
}

// Given a field of view in degrees, compute the corresponding projection
// matrix.
static gvr::Mat4f PerspectiveMatrixFromView(const gvr::Rectf& fov, float z_near,
                                            float z_far) {
  gvr::Mat4f result;
  const float x_left = -std::tan(fov.left * M_PI / 180.0f) * z_near;
  const float x_right = std::tan(fov.right * M_PI / 180.0f) * z_near;
  const float y_bottom = -std::tan(fov.bottom * M_PI / 180.0f) * z_near;
  const float y_top = std::tan(fov.top * M_PI / 180.0f) * z_near;
  const float zero = 0.0f;

  assert(x_left < x_right && y_bottom < y_top && z_near < z_far &&
         z_near > zero && z_far > zero);
  const float X = (2 * z_near) / (x_right - x_left);
  const float Y = (2 * z_near) / (y_top - y_bottom);
  const float A = (x_right + x_left) / (x_right - x_left);
  const float B = (y_top + y_bottom) / (y_top - y_bottom);
  const float C = (z_near + z_far) / (z_near - z_far);
  const float D = (2 * z_near * z_far) / (z_near - z_far);

  for (int i = 0; i < 4; ++i) {
    for (int j = 0; j < 4; ++j) {
      result.m[i][j] = 0.0f;
    }
  }
  result.m[0][0] = X;
  result.m[0][2] = A;
  result.m[1][1] = Y;
  result.m[1][2] = B;
  result.m[2][2] = C;
  result.m[2][3] = D;
  result.m[3][2] = -1;

  return result;
}

// Multiplies both X coordinates of the rectangle by the given width and both Y
// coordinates by the given height.
static gvr::Rectf ModulateRect(const gvr::Rectf& rect, float width,
                               float height) {
  gvr::Rectf result = {rect.left * width, rect.right * width,
                       rect.bottom * height, rect.top * height};
  return result;
}

// Given the size of a texture in pixels and a rectangle in UV coordinates,
// computes the corresponding rectangle in pixel coordinates.
static gvr::Recti CalculatePixelSpaceRect(const gvr::Sizei& texture_size,
                                          const gvr::Rectf& texture_rect) {
  const float width = static_cast<float>(texture_size.width);
  const float height = static_cast<float>(texture_size.height);
  const gvr::Rectf rect = ModulateRect(texture_rect, width, height);
  const gvr::Recti result = {
      static_cast<int>(rect.left), static_cast<int>(rect.right),
      static_cast<int>(rect.bottom), static_cast<int>(rect.top)};
  return result;
}

// Generate a random floating point number between 0 and 1.
static float RandomUniformFloat() {
  static std::random_device random_device;
  static std::mt19937 random_generator(random_device());
  static std::uniform_real_distribution<float> random_distribution(0, 1);
  return random_distribution(random_generator);
}

static void CheckGLError(const char* label) {
  int gl_error = glGetError();
  if (gl_error != GL_NO_ERROR) {
    LOGW("GL error @ %s: %d", label, gl_error);
    // Crash immediately to make OpenGL errors obvious.
    abort();
  }
}

// Computes a texture size that has approximately half as many pixels. This is
// equivalent to scaling each dimension by approximately sqrt(2)/2.
static gvr::Sizei HalfPixelCount(const gvr::Sizei& in) {
  // Scale each dimension by sqrt(2)/2 ~= 7/10ths.
  gvr::Sizei out;
  out.width = (7 * in.width) / 10;
  out.height = (7 * in.height) / 10;
  return out;
}

// Convert the quaternion describing the controller's orientation to a
// rotation matrix.
static gvr::Mat4f ControllerQuatToMatrix(const gvr::ControllerQuat& quat) {
  gvr::Mat4f result;
  const float x = quat.qx;
  const float x2 = quat.qx * quat.qx;
  const float y = quat.qy;
  const float y2 = quat.qy * quat.qy;
  const float z = quat.qz;
  const float z2 = quat.qz * quat.qz;
  const float w = quat.qw;
  const float xy = quat.qx * quat.qy;
  const float xz = quat.qx * quat.qz;
  const float xw = quat.qx * quat.qw;
  const float yz = quat.qy * quat.qz;
  const float yw = quat.qy * quat.qw;
  const float zw = quat.qz * quat.qw;

  const float m11 = 1.0f - 2.0f * y2 - 2.0f * z2;
  const float m12 = 2.0f * (xy - zw);
  const float m13 = 2.0f * (xz + yw);
  const float m21 = 2.0f * (xy + zw);
  const float m22 = 1.0f - 2.0f * x2 - 2.0f * z2;
  const float m23 = 2.0f * (yz - xw);
  const float m31 = 2.0f * (xz - yw);
  const float m32 = 2.0f * (yz + xw);
  const float m33 = 1.0f - 2.0f * x2 - 2.0f * y2;

  return {{{m11, m12, m13, 0.0f},
           {m21, m22, m23, 0.0f},
           {m31, m32, m33, 0.0f},
           {0.0f, 0.0f, 0.0f, 1.0f}}};
}

static inline float VectorNorm(const std::array<float, 4>& vect) {
  return std::sqrt(vect[0] * vect[0] + vect[1] * vect[1] + vect[2] * vect[2]);
}

static float VectorInnerProduct(const std::array<float, 4>& vect1,
                                const std::array<float, 4>& vect2) {
  float product = 0;
  for (int i = 0; i < 3; i++) {
    product += vect1[i] * vect2[i];
  }
  return product;
}
}  // anonymous namespace

TreasureHuntRenderer::TreasureHuntRenderer(
    gvr_context* gvr_context, std::unique_ptr<gvr::AudioApi> gvr_audio_api)
    : gvr_api_(gvr::GvrApi::WrapNonOwned(gvr_context)),
      gvr_audio_api_(std::move(gvr_audio_api)),
      viewport_left_(gvr_api_->CreateBufferViewport()),
      viewport_right_(gvr_api_->CreateBufferViewport()),
      floor_vertices_(world_layout_data_.floor_coords.data()),
      cube_vertices_(world_layout_data_.cube_coords.data()),
      cube_colors_(world_layout_data_.cube_colors.data()),
      cube_found_colors_(world_layout_data_.cube_found_color.data()),
      cube_normals_(world_layout_data_.cube_normals.data()),
      reticle_vertices_(world_layout_data_.reticle_coords.data()),
      reticle_render_size_{128, 128},
      light_pos_world_space_({0.0f, 2.0f, 0.0f, 1.0f}),
      object_distance_(kMinCubeDistance),
      audio_source_id_(-1),
      success_source_id_(-1),
      gvr_controller_api_(nullptr),
      gvr_viewer_type_(gvr_api_->GetViewerType()) {
  ResumeControllerApiAsNeeded();

  LOGD("Built with GVR version: %s", GVR_SDK_VERSION_STRING);
  if (gvr_viewer_type_ == GVR_VIEWER_TYPE_CARDBOARD) {
    LOGD("Viewer type: CARDBOARD");
  } else if (gvr_viewer_type_ == GVR_VIEWER_TYPE_DAYDREAM) {
    LOGD("Viewer type: DAYDREAM");
  } else {
    LOGE("Unexpected viewer type.");
  }
}

TreasureHuntRenderer::~TreasureHuntRenderer() {
  // Join the audio initialization thread in case it still exists.
  if (audio_initialization_thread_.joinable()) {
    audio_initialization_thread_.join();
  }
}

void TreasureHuntRenderer::InitializeGl() {
  gvr_api_->InitializeGl();
  multiview_enabled_ = gvr_api_->IsFeatureSupported(GVR_FEATURE_MULTIVIEW);
  LOGD(multiview_enabled_ ? "Using multiview." : "Not using multiview.");

  int index = multiview_enabled_ ? 1 : 0;
  const int vertex_shader =
      LoadGLShader(GL_VERTEX_SHADER, &kDiffuseLightingVertexShaders[index]);
  const int grid_shader =
      LoadGLShader(GL_FRAGMENT_SHADER, &kGridFragmentShaders[index]);
  const int pass_through_shader =
      LoadGLShader(GL_FRAGMENT_SHADER, &kPassthroughFragmentShaders[index]);
  const int reticle_vertex_shader =
      LoadGLShader(GL_VERTEX_SHADER, &kReticleVertexShaders[index]);
  const int reticle_fragment_shader =
      LoadGLShader(GL_FRAGMENT_SHADER, &kReticleFragmentShaders[index]);

  cube_program_ = glCreateProgram();
  glAttachShader(cube_program_, vertex_shader);
  glAttachShader(cube_program_, pass_through_shader);
  glLinkProgram(cube_program_);
  glUseProgram(cube_program_);

  cube_position_param_ = glGetAttribLocation(cube_program_, "a_Position");
  cube_normal_param_ = glGetAttribLocation(cube_program_, "a_Normal");
  cube_color_param_ = glGetAttribLocation(cube_program_, "a_Color");

  cube_model_param_ = glGetUniformLocation(cube_program_, "u_Model");
  cube_modelview_param_ = glGetUniformLocation(cube_program_, "u_MVMatrix");
  cube_modelview_projection_param_ =
      glGetUniformLocation(cube_program_, "u_MVP");
  cube_light_pos_param_ = glGetUniformLocation(cube_program_, "u_LightPos");

  CheckGLError("Cube program params");

  floor_program_ = glCreateProgram();
  glAttachShader(floor_program_, vertex_shader);
  glAttachShader(floor_program_, grid_shader);
  glLinkProgram(floor_program_);
  glUseProgram(floor_program_);

  CheckGLError("Floor program");

  floor_position_param_ = glGetAttribLocation(floor_program_, "a_Position");
  floor_normal_param_ = glGetAttribLocation(floor_program_, "a_Normal");
  floor_color_param_ = glGetAttribLocation(floor_program_, "a_Color");

  floor_model_param_ = glGetUniformLocation(floor_program_, "u_Model");
  floor_modelview_param_ = glGetUniformLocation(floor_program_, "u_MVMatrix");
  floor_modelview_projection_param_ =
      glGetUniformLocation(floor_program_, "u_MVP");
  floor_light_pos_param_ = glGetUniformLocation(floor_program_, "u_LightPos");

  CheckGLError("Floor program params");

  reticle_program_ = glCreateProgram();
  glAttachShader(reticle_program_, reticle_vertex_shader);
  glAttachShader(reticle_program_, reticle_fragment_shader);
  glLinkProgram(reticle_program_);
  glUseProgram(reticle_program_);

  CheckGLError("Reticle program");

  reticle_position_param_ = glGetAttribLocation(reticle_program_, "a_Position");
  reticle_modelview_projection_param_ =
      glGetUniformLocation(reticle_program_, "u_MVP");

  CheckGLError("Reticle program params");

  // Object first appears directly in front of user.
  model_cube_ = {{{1.0f, 0.0f, 0.0f, 0.0f},
                  {0.0f, 0.707f, -0.707f, 0.0f},
                  {0.0f, 0.707f, 0.707f, -object_distance_},
                  {0.0f, 0.0f, 0.0f, 1.0f}}};
  const float rs = 0.04f;  // Reticle scale.
  model_reticle_ = {{{rs, 0.0f, 0.0f, 0.0f},
                     {0.0f, rs, 0.0f, 0.0f},
                     {0.0f, 0.0f, rs, -kReticleDistance},
                     {0.0f, 0.0f, 0.0f, 1.0f}}};

  // Because we are using 2X MSAA, we can render to half as many pixels and
  // achieve similar quality.
  render_size_ =
      HalfPixelCount(gvr_api_->GetMaximumEffectiveRenderTargetSize());
  std::vector<gvr::BufferSpec> specs;

  specs.push_back(gvr_api_->CreateBufferSpec());
  specs[0].SetColorFormat(GVR_COLOR_FORMAT_RGBA_8888);
  specs[0].SetDepthStencilFormat(GVR_DEPTH_STENCIL_FORMAT_DEPTH_16);
  specs[0].SetSamples(2);

  // With multiview, the distortion buffer is a texture array with two layers
  // whose width is half the display width.
  if (multiview_enabled_) {
    gvr::Sizei half_size = { render_size_.width / 2, render_size_.height };
    specs[0].SetMultiviewLayers(2);
    specs[0].SetSize(half_size);
  } else {
    specs[0].SetSize(render_size_);
  }

  specs.push_back(gvr_api_->CreateBufferSpec());
  specs[1].SetSize(reticle_render_size_);
  specs[1].SetColorFormat(GVR_COLOR_FORMAT_RGBA_8888);
  specs[1].SetDepthStencilFormat(GVR_DEPTH_STENCIL_FORMAT_NONE);
  specs[1].SetSamples(1);
  swapchain_.reset(new gvr::SwapChain(gvr_api_->CreateSwapChain(specs)));

  viewport_list_.reset(
      new gvr::BufferViewportList(gvr_api_->CreateEmptyBufferViewportList()));

  // Initialize audio engine and preload sample in a separate thread to avoid
  // any delay during construction and app initialization. Only do this once.
  if (!audio_initialization_thread_.joinable()) {
    audio_initialization_thread_ =
        std::thread(&TreasureHuntRenderer::LoadAndPlayCubeSound, this);
  }
}

void TreasureHuntRenderer::ResumeControllerApiAsNeeded() {
  switch (gvr_viewer_type_) {
    case GVR_VIEWER_TYPE_CARDBOARD:
      gvr_controller_api_.reset();
      break;
    case GVR_VIEWER_TYPE_DAYDREAM:
      if (!gvr_controller_api_) {
        // Initialized controller api.
        gvr_controller_api_.reset(new gvr::ControllerApi);
        CHECK(gvr_controller_api_);
        CHECK(gvr_controller_api_->Init(gvr::ControllerApi::DefaultOptions(),
                                        gvr_api_->cobj()));
      }
      gvr_controller_api_->Resume();
      break;
    default:
      LOGE("unexpected viewer type.");
      break;
  }
}

void TreasureHuntRenderer::ProcessControllerInput() {
  if (gvr_viewer_type_ == GVR_VIEWER_TYPE_CARDBOARD) return;
  const int old_status = gvr_controller_state_.GetApiStatus();
  const int old_connection_state = gvr_controller_state_.GetConnectionState();

  // Read current controller state.
  gvr_controller_state_.Update(*gvr_controller_api_);

  // Print new API status and connection state, if they changed.
  if (gvr_controller_state_.GetApiStatus() != old_status ||
      gvr_controller_state_.GetConnectionState() != old_connection_state) {
    LOGD("TreasureHuntApp: controller API status: %s, connection state: %s",
         gvr_controller_api_status_to_string(
             gvr_controller_state_.GetApiStatus()),
         gvr_controller_connection_state_to_string(
             gvr_controller_state_.GetConnectionState()));
  }

  // Trigger click event if app/click button is clicked.
  if (gvr_controller_state_.GetButtonDown(GVR_CONTROLLER_BUTTON_APP) ||
      gvr_controller_state_.GetButtonDown(GVR_CONTROLLER_BUTTON_CLICK)) {
    OnTriggerEvent();
  }
}

void TreasureHuntRenderer::UpdateReticlePosition() {
  if (gvr_viewer_type_ == GVR_VIEWER_TYPE_DAYDREAM) {
    ProcessControllerInput();
    gvr::Mat4f controller_matrix =
        ControllerQuatToMatrix(gvr_controller_state_.GetOrientation());
    modelview_reticle_ =
        MatrixMul(head_view_, MatrixMul(controller_matrix, model_reticle_));
  } else {
    modelview_reticle_ = model_reticle_;
  }
}

void TreasureHuntRenderer::DrawFrame() {
  PrepareFramebuffer();
  gvr::Frame frame = swapchain_->AcquireFrame();

  // A client app does its rendering here.
  gvr::ClockTimePoint target_time = gvr::GvrApi::GetTimePointNow();
  target_time.monotonic_system_time_nanos += kPredictionTimeWithoutVsyncNanos;
  gvr::BufferViewport* viewport[2] = {
    &viewport_left_,
    &viewport_right_,
  };
  // Note that neck model application is a no-op if the viewer supports 6DoF
  // head tracking
  head_view_ = gvr_api_->ApplyNeckModel(
      gvr_api_->GetHeadSpaceFromStartSpaceTransform(target_time),
      kNeckModelFactor);
  viewport_list_->SetToRecommendedBufferViewports();

  gvr::BufferViewport reticle_viewport = gvr_api_->CreateBufferViewport();
  reticle_viewport.SetSourceBufferIndex(1);
  if (gvr_viewer_type_ == GVR_VIEWER_TYPE_CARDBOARD) {
    // Do not reproject the reticle if it's head-locked.
    reticle_viewport.SetReprojection(GVR_REPROJECTION_NONE);
  }
  const gvr_rectf fullscreen = { 0, 1, 0, 1 };
  reticle_viewport.SetSourceUv(fullscreen);
  UpdateReticlePosition();

  gvr::Value floor_height;
  // This may change when the floor height changes so it's computed every frame.
  float ground_y = gvr_api_->GetCurrentProperties().Get(
                       GVR_PROPERTY_TRACKING_FLOOR_HEIGHT, &floor_height)
                       ? floor_height.f
                       : kDefaultFloorHeight;
  model_floor_ = {{{1.0f, 0.0f, 0.0f, 0.0f},
                   {0.0f, 1.0f, 0.0f, ground_y},
                   {0.0f, 0.0f, 1.0f, 0.0f},
                   {0.0f, 0.0f, 0.0f, 1.0f}}};

  gvr::Mat4f eye_views[2];
  for (int eye = 0; eye < 2; ++eye) {
    const gvr::Eye gvr_eye = eye == 0 ? GVR_LEFT_EYE : GVR_RIGHT_EYE;
    const gvr::Mat4f eye_from_head = gvr_api_->GetEyeFromHeadMatrix(gvr_eye);
    eye_views[eye] = MatrixMul(eye_from_head, head_view_);

    viewport_list_->GetBufferViewport(eye, viewport[eye]);

    if (multiview_enabled_) {
      viewport[eye]->SetSourceUv(fullscreen);
      viewport[eye]->SetSourceLayer(eye);
      viewport_list_->SetBufferViewport(eye, *viewport[eye]);
    }

    reticle_viewport.SetTransform(MatrixMul(eye_from_head, modelview_reticle_));
    reticle_viewport.SetTargetEye(gvr_eye);
    // The first two viewports are for the 3D scene (one for each eye), the
    // latter two viewports are for the reticle (one for each eye).
    viewport_list_->SetBufferViewport(2 + eye, reticle_viewport);

    modelview_cube_[eye] = MatrixMul(eye_views[eye], model_cube_);
    modelview_floor_[eye] = MatrixMul(eye_views[eye], model_floor_);
    const gvr_rectf fov = viewport[eye]->GetSourceFov();
    const gvr::Mat4f perspective =
        PerspectiveMatrixFromView(fov, kZNear, kZFar);
    modelview_projection_cube_[eye] =
        MatrixMul(perspective, modelview_cube_[eye]);
    modelview_projection_floor_[eye] =
        MatrixMul(perspective, modelview_floor_[eye]);
    light_pos_eye_space_[eye] =
        Vec4ToVec3(MatrixVectorMul(eye_views[eye], light_pos_world_space_));
  }

  glEnable(GL_DEPTH_TEST);
  glEnable(GL_CULL_FACE);
  glDisable(GL_SCISSOR_TEST);
  glDisable(GL_BLEND);

  // Draw the world.
  frame.BindBuffer(0);
  glClearColor(0.1f, 0.1f, 0.1f, 0.5f);  // Dark background so text shows up.
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  if (multiview_enabled_) {
    DrawWorld(kMultiview);
  } else {
    DrawWorld(kLeftView);
    DrawWorld(kRightView);
  }
  frame.Unbind();

  // Draw the reticle on a separate layer.
  frame.BindBuffer(1);
  glClearColor(0.0f, 0.0f, 0.0f, 0.0f);  // Transparent background.
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  DrawReticle();
  frame.Unbind();

  // Submit frame.
  frame.Submit(*viewport_list_, head_view_);

  CheckGLError("onDrawFrame");

  // Update audio head rotation in audio API.
  gvr_audio_api_->SetHeadPose(head_view_);
  gvr_audio_api_->Update();
}

void TreasureHuntRenderer::PrepareFramebuffer() {
  // Because we are using 2X MSAA, we can render to half as many pixels and
  // achieve similar quality.
  const gvr::Sizei recommended_size =
      HalfPixelCount(gvr_api_->GetMaximumEffectiveRenderTargetSize());
  if (render_size_.width != recommended_size.width ||
      render_size_.height != recommended_size.height) {
    // We need to resize the framebuffer. Note that multiview uses two texture
    // layers, each with half the render width.
    gvr::Sizei framebuffer_size = recommended_size;
    if (multiview_enabled_) {
      framebuffer_size.width /= 2;
    }
    swapchain_->ResizeBuffer(0, framebuffer_size);
    render_size_ = recommended_size;
  }
}

void TreasureHuntRenderer::OnTriggerEvent() {
  if (IsPointingAtObject()) {
    success_source_id_ = gvr_audio_api_->CreateStereoSound(kSuccessSoundFile);
    gvr_audio_api_->PlaySound(success_source_id_, false /* looping disabled */);
    HideObject();
  }
}

void TreasureHuntRenderer::OnPause() {
  gvr_api_->PauseTracking();
  gvr_audio_api_->Pause();
  if (gvr_controller_api_) gvr_controller_api_->Pause();
}

void TreasureHuntRenderer::OnResume() {
  gvr_api_->ResumeTracking();
  gvr_api_->RefreshViewerProfile();
  gvr_audio_api_->Resume();
  gvr_viewer_type_ = gvr_api_->GetViewerType();
  ResumeControllerApiAsNeeded();
}

/**
 * Converts a raw text file, saved as a resource, into an OpenGL ES shader.
 *
 * @param type  The type of shader we will be creating.
 * @param resId The resource ID of the raw text file.
 * @return The shader object handler.
 */
int TreasureHuntRenderer::LoadGLShader(int type, const char** shadercode) {
  int shader = glCreateShader(type);
  glShaderSource(shader, 1, shadercode, nullptr);
  glCompileShader(shader);

  // Get the compilation status.
  int compileStatus;
  glGetShaderiv(shader, GL_COMPILE_STATUS, &compileStatus);

  // If the compilation failed, delete the shader.
  if (compileStatus == 0) {
    glDeleteShader(shader);
    shader = 0;
  }

  return shader;
}

/**
 * Draws a frame for a particular view.
 *
 * @param view The view to render: left, right, or both (multiview).
 */
void TreasureHuntRenderer::DrawWorld(ViewType view) {
  if (view == kMultiview) {
    glViewport(0, 0, render_size_.width / 2, render_size_.height);
  } else {
    const gvr::BufferViewport& viewport =
        view == kLeftView ? viewport_left_ : viewport_right_;
    const gvr::Recti pixel_rect =
        CalculatePixelSpaceRect(render_size_, viewport.GetSourceUv());
    glViewport(pixel_rect.left, pixel_rect.bottom,
               pixel_rect.right - pixel_rect.left,
               pixel_rect.top - pixel_rect.bottom);
  }
  DrawCube(view);
  DrawFloor(view);
}

void TreasureHuntRenderer::DrawCube(ViewType view) {
  glUseProgram(cube_program_);

  if (view == kMultiview) {
    glUniform3fv(cube_light_pos_param_, 2,
                 VectorPairToGLArray(light_pos_eye_space_).data());
    glUniformMatrix4fv(cube_modelview_param_, 2, GL_FALSE,
                       MatrixPairToGLArray(modelview_cube_).data());
    glUniformMatrix4fv(cube_modelview_projection_param_, 2, GL_FALSE,
                       MatrixPairToGLArray(modelview_projection_cube_).data());
  } else {
    glUniform3fv(cube_light_pos_param_, 1, light_pos_eye_space_[view].data());
    glUniformMatrix4fv(cube_modelview_param_, 1, GL_FALSE,
                       MatrixToGLArray(modelview_cube_[view]).data());
    glUniformMatrix4fv(
        cube_modelview_projection_param_, 1, GL_FALSE,
        MatrixToGLArray(modelview_projection_cube_[view]).data());
  }

  // Set the Model in the shader, used to calculate lighting
  glUniformMatrix4fv(cube_model_param_, 1, GL_FALSE,
                     MatrixToGLArray(model_cube_).data());

  // Set the position of the cube
  glVertexAttribPointer(cube_position_param_, kCoordsPerVertex, GL_FLOAT, false,
                        0, cube_vertices_);
  glEnableVertexAttribArray(cube_position_param_);

  // Set the normal positions of the cube, again for shading
  glVertexAttribPointer(cube_normal_param_, 3, GL_FLOAT, false, 0,
                        cube_normals_);
  glEnableVertexAttribArray(cube_normal_param_);

  // Set vertex colors
  if (IsPointingAtObject()) {
    const float* found_color = world_layout_data_.cube_found_color.data();
    glVertexAttrib4f(cube_color_param_, found_color[0], found_color[1],
                     found_color[2], 1.0f);
    glDisableVertexAttribArray(cube_color_param_);
  } else {
    glVertexAttribPointer(cube_color_param_, 3, GL_FLOAT, false, 0,
                          cube_colors_);
    glEnableVertexAttribArray(cube_color_param_);
  }

  glDrawArrays(GL_TRIANGLES, 0, 36);

  glDisableVertexAttribArray(cube_position_param_);
  glDisableVertexAttribArray(cube_normal_param_);
  glDisableVertexAttribArray(cube_color_param_);

  CheckGLError("Drawing cube");
}

void TreasureHuntRenderer::DrawFloor(ViewType view) {
  glUseProgram(floor_program_);

  if (view == kMultiview) {
    glUniform3fv(floor_light_pos_param_, 2,
                 VectorPairToGLArray(light_pos_eye_space_).data());
    glUniformMatrix4fv(floor_modelview_param_, 2, GL_FALSE,
                       MatrixPairToGLArray(modelview_floor_).data());
    glUniformMatrix4fv(floor_modelview_projection_param_, 2, GL_FALSE,
                       MatrixPairToGLArray(modelview_projection_floor_).data());
  } else {
    glUniform3fv(floor_light_pos_param_, 1, light_pos_eye_space_[view].data());
    glUniformMatrix4fv(floor_modelview_param_, 1, GL_FALSE,
                       MatrixToGLArray(modelview_floor_[view]).data());
    glUniformMatrix4fv(
        floor_modelview_projection_param_, 1, GL_FALSE,
        MatrixToGLArray(modelview_projection_floor_[view]).data());
  }

  glUniformMatrix4fv(floor_model_param_, 1, GL_FALSE,
                     MatrixToGLArray(model_floor_).data());
  glVertexAttribPointer(floor_position_param_, kCoordsPerVertex, GL_FLOAT,
                        false, 0, floor_vertices_);
  glVertexAttrib3f(floor_normal_param_, 0.0f, 1.0f, 0.0f);
  glVertexAttrib4f(floor_color_param_, 0.0f, 0.3398f, 0.9023f, 1.0f);

  glEnableVertexAttribArray(floor_position_param_);
  glDrawArrays(GL_TRIANGLES, 0, 24);
  glDisableVertexAttribArray(floor_position_param_);

  CheckGLError("Drawing floor");
}

void TreasureHuntRenderer::DrawReticle() {
  glViewport(0, 0, reticle_render_size_.width, reticle_render_size_.height);
  glUseProgram(reticle_program_);
  const gvr::Mat4f uniform_matrix = {{{1.f, 0.f, 0.f, 0.f},
                                      {0.f, 1.f, 0.f, 0.f},
                                      {0.f, 0.f, 1.f, 0.f},
                                      {0.f, 0.f, 0.f, 1.f}}};
  glUniformMatrix4fv(reticle_modelview_projection_param_, 1, GL_FALSE,
                     MatrixToGLArray(uniform_matrix).data());
  glVertexAttribPointer(reticle_position_param_, kCoordsPerVertex, GL_FLOAT,
                        false, 0, reticle_vertices_);
  glEnableVertexAttribArray(reticle_position_param_);
  glDrawArrays(GL_TRIANGLES, 0, 6);
  glDisableVertexAttribArray(reticle_position_param_);

  CheckGLError("Drawing reticle");
}

void TreasureHuntRenderer::HideObject() {
  std::array<float, 4> cube_position = {
      model_cube_.m[0][3], model_cube_.m[1][3], model_cube_.m[2][3], 1.f};

  // First rotate in XZ plane, between pi/2 and 3pi/2 radians away, apply this
  // to model_cube_ to keep the front face of the cube towards the user.
  float angle_xz = M_PI * (RandomUniformFloat() + 0.5f);
  gvr::Mat4f rotation_matrix = {{{cosf(angle_xz), 0.f, -sinf(angle_xz), 0.f},
                                 {0.f, 1.f, 0.f, 0.f},
                                 {sinf(angle_xz), 0.f, cosf(angle_xz), 0.f},
                                 {0.f, 0.f, 0.f, 1.f}}};
  cube_position = MatrixVectorMul(rotation_matrix, cube_position);
  model_cube_ = MatrixMul(rotation_matrix, model_cube_);

  // Pick a new distance for the cube, and apply that scale to the position.
  const float old_object_distance = object_distance_;
  object_distance_ =
      RandomUniformFloat() * (kMaxCubeDistance - kMinCubeDistance) +
      kMinCubeDistance;
  const float scale = object_distance_ / old_object_distance;
  cube_position[0] *= scale;
  cube_position[1] *= scale;
  cube_position[2] *= scale;

  // Choose a random yaw for the cube between 0 and pi/4.
  const float yaw = M_PI * (RandomUniformFloat()) / 4.0f;
  cube_position[1] = tanf(yaw) * object_distance_;

  model_cube_.m[0][3] = cube_position[0];
  model_cube_.m[1][3] = cube_position[1];
  model_cube_.m[2][3] = cube_position[2];

  if (audio_source_id_ >= 0) {
    gvr_audio_api_->SetSoundObjectPosition(audio_source_id_, cube_position[0],
                                           cube_position[1], cube_position[2]);
  }
}

bool TreasureHuntRenderer::IsPointingAtObject() {
  // Compute vectors pointing towards the reticle and towards the cube in head
  // space.
  gvr::Mat4f head_from_reticle = modelview_reticle_;
  gvr::Mat4f head_from_cube = MatrixMul(head_view_, model_cube_);
  const std::array<float, 4> reticle_vector =
      MatrixVectorMul(head_from_reticle, {0.f, 0.f, 0.f, 1.f});
  const std::array<float, 4> cube_vector =
      MatrixVectorMul(head_from_cube, {0.f, 0.f, 0.f, 1.f});

  // Compute the angle between the vector towards the reticle and the vector
  // towards the cube by computing the arc cosine of their normalized dot
  // product.
  float angle = std::acos(std::max(-1.f, std::min(1.f,
      VectorInnerProduct(reticle_vector, cube_vector) /
      VectorNorm(reticle_vector) / VectorNorm(cube_vector))));
  return angle < kAngleLimit;
}

void TreasureHuntRenderer::LoadAndPlayCubeSound() {
  // Preload sound files.
  gvr_audio_api_->PreloadSoundfile(kObjectSoundFile);
  gvr_audio_api_->PreloadSoundfile(kSuccessSoundFile);
  // Create sound file handler from preloaded sound file.
  audio_source_id_ = gvr_audio_api_->CreateSoundObject(kObjectSoundFile);
  // Set sound object to current cube position.
  gvr_audio_api_->SetSoundObjectPosition(audio_source_id_, model_cube_.m[0][3],
                                         model_cube_.m[1][3],
                                         model_cube_.m[2][3]);
  // Trigger sound object playback.
  gvr_audio_api_->PlaySound(audio_source_id_, true /* looped playback */);
}