1// Copyright 2013 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5// This example program is based on Simple_VertexShader.c from:
6
7//
8// Book:      OpenGL(R) ES 2.0 Programming Guide
9// Authors:   Aaftab Munshi, Dan Ginsburg, Dave Shreiner
10// ISBN-10:   0321502795
11// ISBN-13:   9780321502797
12// Publisher: Addison-Wesley Professional
13// URLs:      http://safari.informit.com/9780321563835
14//            http://www.opengles-book.com
15//
16
17#include "mojo/examples/sample_app/spinning_cube.h"
18
19#include <math.h>
20#include <stdlib.h>
21#include <string.h>
22#include <GLES2/gl2.h>
23#include <GLES2/gl2ext.h>
24
25namespace examples {
26
27namespace {
28
29const float kPi = 3.14159265359f;
30
31int GenerateCube(GLuint *vbo_vertices,
32                 GLuint *vbo_indices) {
33  const int num_indices = 36;
34
35  const GLfloat cube_vertices[] = {
36    -0.5f, -0.5f, -0.5f,
37    -0.5f, -0.5f,  0.5f,
38    0.5f, -0.5f,  0.5f,
39    0.5f, -0.5f, -0.5f,
40    -0.5f,  0.5f, -0.5f,
41    -0.5f,  0.5f,  0.5f,
42    0.5f,  0.5f,  0.5f,
43    0.5f,  0.5f, -0.5f,
44    -0.5f, -0.5f, -0.5f,
45    -0.5f,  0.5f, -0.5f,
46    0.5f,  0.5f, -0.5f,
47    0.5f, -0.5f, -0.5f,
48    -0.5f, -0.5f, 0.5f,
49    -0.5f,  0.5f, 0.5f,
50    0.5f,  0.5f, 0.5f,
51    0.5f, -0.5f, 0.5f,
52    -0.5f, -0.5f, -0.5f,
53    -0.5f, -0.5f,  0.5f,
54    -0.5f,  0.5f,  0.5f,
55    -0.5f,  0.5f, -0.5f,
56    0.5f, -0.5f, -0.5f,
57    0.5f, -0.5f,  0.5f,
58    0.5f,  0.5f,  0.5f,
59    0.5f,  0.5f, -0.5f,
60  };
61
62  const GLushort cube_indices[] = {
63    0, 2, 1,
64    0, 3, 2,
65    4, 5, 6,
66    4, 6, 7,
67    8, 9, 10,
68    8, 10, 11,
69    12, 15, 14,
70    12, 14, 13,
71    16, 17, 18,
72    16, 18, 19,
73    20, 23, 22,
74    20, 22, 21
75  };
76
77  if (vbo_vertices) {
78    glGenBuffers(1, vbo_vertices);
79    glBindBuffer(GL_ARRAY_BUFFER, *vbo_vertices);
80    glBufferData(GL_ARRAY_BUFFER,
81                 sizeof(cube_vertices),
82                 cube_vertices,
83                 GL_STATIC_DRAW);
84    glBindBuffer(GL_ARRAY_BUFFER, 0);
85  }
86
87  if (vbo_indices) {
88    glGenBuffers(1, vbo_indices);
89    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, *vbo_indices);
90    glBufferData(GL_ELEMENT_ARRAY_BUFFER,
91                 sizeof(cube_indices),
92                 cube_indices,
93                 GL_STATIC_DRAW);
94    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
95  }
96
97  return num_indices;
98}
99
100GLuint LoadShader(GLenum type,
101                  const char* shader_source) {
102  GLuint shader = glCreateShader(type);
103  glShaderSource(shader, 1, &shader_source, NULL);
104  glCompileShader(shader);
105
106  GLint compiled = 0;
107  glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
108
109  if (!compiled) {
110    glDeleteShader(shader);
111    return 0;
112  }
113
114  return shader;
115}
116
117GLuint LoadProgram(const char* vertext_shader_source,
118                   const char* fragment_shader_source) {
119  GLuint vertex_shader = LoadShader(GL_VERTEX_SHADER,
120                                    vertext_shader_source);
121  if (!vertex_shader)
122    return 0;
123
124  GLuint fragment_shader = LoadShader(GL_FRAGMENT_SHADER,
125                                      fragment_shader_source);
126  if (!fragment_shader) {
127    glDeleteShader(vertex_shader);
128    return 0;
129  }
130
131  GLuint program_object = glCreateProgram();
132  glAttachShader(program_object, vertex_shader);
133  glAttachShader(program_object, fragment_shader);
134
135  glLinkProgram(program_object);
136
137  glDeleteShader(vertex_shader);
138  glDeleteShader(fragment_shader);
139
140  GLint linked = 0;
141  glGetProgramiv(program_object, GL_LINK_STATUS, &linked);
142
143  if (!linked) {
144    glDeleteProgram(program_object);
145    return 0;
146  }
147
148  return program_object;
149}
150
151class ESMatrix {
152 public:
153  GLfloat m[4][4];
154
155  ESMatrix() {
156    LoadZero();
157  }
158
159  void LoadZero() {
160    memset(this, 0x0, sizeof(ESMatrix));
161  }
162
163  void LoadIdentity() {
164    LoadZero();
165    m[0][0] = 1.0f;
166    m[1][1] = 1.0f;
167    m[2][2] = 1.0f;
168    m[3][3] = 1.0f;
169  }
170
171  void Multiply(ESMatrix* a, ESMatrix* b) {
172    ESMatrix result;
173    for (int i = 0; i < 4; ++i) {
174      result.m[i][0] = (a->m[i][0] * b->m[0][0]) +
175                       (a->m[i][1] * b->m[1][0]) +
176                       (a->m[i][2] * b->m[2][0]) +
177                       (a->m[i][3] * b->m[3][0]);
178
179      result.m[i][1] = (a->m[i][0] * b->m[0][1]) +
180                       (a->m[i][1] * b->m[1][1]) +
181                       (a->m[i][2] * b->m[2][1]) +
182                       (a->m[i][3] * b->m[3][1]);
183
184      result.m[i][2] = (a->m[i][0] * b->m[0][2]) +
185                       (a->m[i][1] * b->m[1][2]) +
186                       (a->m[i][2] * b->m[2][2]) +
187                       (a->m[i][3] * b->m[3][2]);
188
189      result.m[i][3] = (a->m[i][0] * b->m[0][3]) +
190                       (a->m[i][1] * b->m[1][3]) +
191                       (a->m[i][2] * b->m[2][3]) +
192                       (a->m[i][3] * b->m[3][3]);
193    }
194    *this = result;
195  }
196
197  void Frustum(float left,
198               float right,
199               float bottom,
200               float top,
201               float near_z,
202               float far_z) {
203    float delta_x = right - left;
204    float delta_y = top - bottom;
205    float delta_z = far_z - near_z;
206
207    if ((near_z <= 0.0f) ||
208        (far_z <= 0.0f) ||
209        (delta_z <= 0.0f) ||
210        (delta_y <= 0.0f) ||
211        (delta_y <= 0.0f))
212      return;
213
214    ESMatrix frust;
215    frust.m[0][0] = 2.0f * near_z / delta_x;
216    frust.m[0][1] = frust.m[0][2] = frust.m[0][3] = 0.0f;
217
218    frust.m[1][1] = 2.0f * near_z / delta_y;
219    frust.m[1][0] = frust.m[1][2] = frust.m[1][3] = 0.0f;
220
221    frust.m[2][0] = (right + left) / delta_x;
222    frust.m[2][1] = (top + bottom) / delta_y;
223    frust.m[2][2] = -(near_z + far_z) / delta_z;
224    frust.m[2][3] = -1.0f;
225
226    frust.m[3][2] = -2.0f * near_z * far_z / delta_z;
227    frust.m[3][0] = frust.m[3][1] = frust.m[3][3] = 0.0f;
228
229    Multiply(&frust, this);
230  }
231
232  void Perspective(float fov_y, float aspect, float near_z, float far_z) {
233    GLfloat frustum_h = tanf(fov_y / 360.0f * kPi) * near_z;
234    GLfloat frustum_w = frustum_h * aspect;
235    Frustum(-frustum_w, frustum_w, -frustum_h, frustum_h, near_z, far_z);
236  }
237
238  void Translate(GLfloat tx, GLfloat ty, GLfloat tz) {
239    m[3][0] += m[0][0] * tx + m[1][0] * ty + m[2][0] * tz;
240    m[3][1] += m[0][1] * tx + m[1][1] * ty + m[2][1] * tz;
241    m[3][2] += m[0][2] * tx + m[1][2] * ty + m[2][2] * tz;
242    m[3][3] += m[0][3] * tx + m[1][3] * ty + m[2][3] * tz;
243  }
244
245  void Rotate(GLfloat angle, GLfloat x, GLfloat y, GLfloat z) {
246    GLfloat mag = sqrtf(x * x + y * y + z * z);
247
248    GLfloat sin_angle = sinf(angle * kPi / 180.0f);
249    GLfloat cos_angle = cosf(angle * kPi / 180.0f);
250    if (mag > 0.0f) {
251      GLfloat xx, yy, zz, xy, yz, zx, xs, ys, zs;
252      GLfloat one_minus_cos;
253      ESMatrix rotation;
254
255      x /= mag;
256      y /= mag;
257      z /= mag;
258
259      xx = x * x;
260      yy = y * y;
261      zz = z * z;
262      xy = x * y;
263      yz = y * z;
264      zx = z * x;
265      xs = x * sin_angle;
266      ys = y * sin_angle;
267      zs = z * sin_angle;
268      one_minus_cos = 1.0f - cos_angle;
269
270      rotation.m[0][0] = (one_minus_cos * xx) + cos_angle;
271      rotation.m[0][1] = (one_minus_cos * xy) - zs;
272      rotation.m[0][2] = (one_minus_cos * zx) + ys;
273      rotation.m[0][3] = 0.0F;
274
275      rotation.m[1][0] = (one_minus_cos * xy) + zs;
276      rotation.m[1][1] = (one_minus_cos * yy) + cos_angle;
277      rotation.m[1][2] = (one_minus_cos * yz) - xs;
278      rotation.m[1][3] = 0.0F;
279
280      rotation.m[2][0] = (one_minus_cos * zx) - ys;
281      rotation.m[2][1] = (one_minus_cos * yz) + xs;
282      rotation.m[2][2] = (one_minus_cos * zz) + cos_angle;
283      rotation.m[2][3] = 0.0F;
284
285      rotation.m[3][0] = 0.0F;
286      rotation.m[3][1] = 0.0F;
287      rotation.m[3][2] = 0.0F;
288      rotation.m[3][3] = 1.0F;
289
290      Multiply(&rotation, this);
291    }
292  }
293};
294
295float RotationForTimeDelta(float delta_time) {
296  return delta_time * 40.0f;
297}
298
299float RotationForDragDistance(float drag_distance) {
300  return drag_distance / 5; // Arbitrary damping.
301}
302
303}  // namespace
304
305class SpinningCube::GLState {
306 public:
307  GLState();
308
309  void OnGLContextLost();
310
311  GLfloat angle_;  // Survives losing the GL context.
312
313  GLuint program_object_;
314  GLint position_location_;
315  GLint mvp_location_;
316  GLint color_location_;
317  GLuint vbo_vertices_;
318  GLuint vbo_indices_;
319  int num_indices_;
320  ESMatrix mvp_matrix_;
321};
322
323SpinningCube::GLState::GLState()
324    : angle_(0) {
325  OnGLContextLost();
326}
327
328void SpinningCube::GLState::OnGLContextLost() {
329  program_object_ = 0;
330  position_location_ = 0;
331  mvp_location_ = 0;
332  color_location_ = 0;
333  vbo_vertices_ = 0;
334  vbo_indices_ = 0;
335  num_indices_ = 0;
336}
337
338SpinningCube::SpinningCube()
339    : initialized_(false),
340      width_(0),
341      height_(0),
342      state_(new GLState()),
343      fling_multiplier_(1.0f),
344      direction_(1),
345      color_() {
346  state_->angle_ = 45.0f;
347  set_color(0.0, 1.0, 0.0);
348}
349
350SpinningCube::~SpinningCube() {
351  if (!initialized_)
352    return;
353  if (state_->vbo_vertices_)
354    glDeleteBuffers(1, &state_->vbo_vertices_);
355  if (state_->vbo_indices_)
356    glDeleteBuffers(1, &state_->vbo_indices_);
357  if (state_->program_object_)
358    glDeleteProgram(state_->program_object_);
359}
360
361void SpinningCube::Init(uint32_t width, uint32_t height) {
362  width_ = width;
363  height_ = height;
364
365  const char vertext_shader_source[] =
366      "uniform mat4 u_mvpMatrix;                   \n"
367      "attribute vec4 a_position;                  \n"
368      "void main()                                 \n"
369      "{                                           \n"
370      "   gl_Position = u_mvpMatrix * a_position;  \n"
371      "}                                           \n";
372
373  const char fragment_shader_source[] =
374      "precision mediump float;                            \n"
375      "uniform vec4 u_color;                               \n"
376      "void main()                                         \n"
377      "{                                                   \n"
378      "  gl_FragColor = u_color;                           \n"
379      "}                                                   \n";
380
381  state_->program_object_ = LoadProgram(
382      vertext_shader_source, fragment_shader_source);
383  state_->position_location_ = glGetAttribLocation(
384      state_->program_object_, "a_position");
385  state_->mvp_location_ = glGetUniformLocation(
386      state_->program_object_, "u_mvpMatrix");
387  state_->color_location_ = glGetUniformLocation(
388      state_->program_object_, "u_color");
389  state_->num_indices_ = GenerateCube(
390      &state_->vbo_vertices_, &state_->vbo_indices_);
391
392  glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
393  initialized_ = true;
394}
395
396void SpinningCube::OnGLContextLost() {
397  initialized_ = false;
398  height_ = 0;
399  width_ = 0;
400  state_->OnGLContextLost();
401}
402
403void SpinningCube::SetFlingMultiplier(float drag_distance,
404                                      float drag_time) {
405  fling_multiplier_ = RotationForDragDistance(drag_distance) /
406      RotationForTimeDelta(drag_time);
407
408}
409
410void SpinningCube::UpdateForTimeDelta(float delta_time) {
411  state_->angle_ += RotationForTimeDelta(delta_time) * fling_multiplier_;
412  if (state_->angle_ >= 360.0f)
413    state_->angle_ -= 360.0f;
414
415  // Arbitrary 50-step linear reduction in spin speed.
416  if (fling_multiplier_ > 1.0f) {
417    fling_multiplier_ =
418        std::max(1.0f, fling_multiplier_ - (fling_multiplier_ - 1.0f) / 50);
419  }
420
421  Update();
422}
423
424void SpinningCube::UpdateForDragDistance(float distance) {
425  state_->angle_ += RotationForDragDistance(distance);
426  if (state_->angle_ >= 360.0f )
427    state_->angle_ -= 360.0f;
428
429  Update();
430}
431
432void SpinningCube::Draw() {
433  glViewport(0, 0, width_, height_);
434  glClear(GL_COLOR_BUFFER_BIT);
435  glUseProgram(state_->program_object_);
436  glBindBuffer(GL_ARRAY_BUFFER, state_->vbo_vertices_);
437  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, state_->vbo_indices_);
438  glVertexAttribPointer(state_->position_location_,
439                           3,
440                           GL_FLOAT,
441                           GL_FALSE, 3 * sizeof(GLfloat),
442                           0);
443  glEnableVertexAttribArray(state_->position_location_);
444  glUniformMatrix4fv(state_->mvp_location_,
445                        1,
446                        GL_FALSE,
447                        (GLfloat*) &state_->mvp_matrix_.m[0][0]);
448  glUniform4f(state_->color_location_, color_[0], color_[1], color_[2], 1.0);
449  glDrawElements(GL_TRIANGLES,
450                    state_->num_indices_,
451                    GL_UNSIGNED_SHORT,
452                    0);
453}
454
455void SpinningCube::Update() {
456  float aspect = static_cast<GLfloat>(width_) / static_cast<GLfloat>(height_);
457
458  ESMatrix perspective;
459  perspective.LoadIdentity();
460  perspective.Perspective(60.0f, aspect, 1.0f, 20.0f );
461
462  ESMatrix modelview;
463  modelview.LoadIdentity();
464  modelview.Translate(0.0, 0.0, -2.0);
465  modelview.Rotate(state_->angle_ * direction_, 1.0, 0.0, 1.0);
466
467  state_->mvp_matrix_.Multiply(&modelview, &perspective);
468}
469
470}  // namespace examples
471