spinning_cube.cc revision a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7 
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 mojo {
26namespace examples {
27
28namespace {
29
30const float kPi = 3.14159265359f;
31
32int GenerateCube(GLuint *vbo_vertices,
33                 GLuint *vbo_indices) {
34  const int num_indices = 36;
35
36  const GLfloat cube_vertices[] = {
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    0.5f,  0.5f, -0.5f,
61  };
62
63  const GLushort cube_indices[] = {
64    0, 2, 1,
65    0, 3, 2,
66    4, 5, 6,
67    4, 6, 7,
68    8, 9, 10,
69    8, 10, 11,
70    12, 15, 14,
71    12, 14, 13,
72    16, 17, 18,
73    16, 18, 19,
74    20, 23, 22,
75    20, 22, 21
76  };
77
78  if (vbo_vertices) {
79    glGenBuffers(1, vbo_vertices);
80    glBindBuffer(GL_ARRAY_BUFFER, *vbo_vertices);
81    glBufferData(GL_ARRAY_BUFFER,
82                 sizeof(cube_vertices),
83                 cube_vertices,
84                 GL_STATIC_DRAW);
85    glBindBuffer(GL_ARRAY_BUFFER, 0);
86  }
87
88  if (vbo_indices) {
89    glGenBuffers(1, vbo_indices);
90    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, *vbo_indices);
91    glBufferData(GL_ELEMENT_ARRAY_BUFFER,
92                 sizeof(cube_indices),
93                 cube_indices,
94                 GL_STATIC_DRAW);
95    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
96  }
97
98  return num_indices;
99}
100
101GLuint LoadShader(GLenum type,
102                  const char* shader_source) {
103  GLuint shader = glCreateShader(type);
104  glShaderSource(shader, 1, &shader_source, NULL);
105  glCompileShader(shader);
106
107  GLint compiled = 0;
108  glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
109
110  if (!compiled) {
111    glDeleteShader(shader);
112    return 0;
113  }
114
115  return shader;
116}
117
118GLuint LoadProgram(const char* vertext_shader_source,
119                   const char* fragment_shader_source) {
120  GLuint vertex_shader = LoadShader(GL_VERTEX_SHADER,
121                                    vertext_shader_source);
122  if (!vertex_shader)
123    return 0;
124
125  GLuint fragment_shader = LoadShader(GL_FRAGMENT_SHADER,
126                                      fragment_shader_source);
127  if (!fragment_shader) {
128    glDeleteShader(vertex_shader);
129    return 0;
130  }
131
132  GLuint program_object = glCreateProgram();
133  glAttachShader(program_object, vertex_shader);
134  glAttachShader(program_object, fragment_shader);
135
136  glLinkProgram(program_object);
137
138  glDeleteShader(vertex_shader);
139  glDeleteShader(fragment_shader);
140
141  GLint linked = 0;
142  glGetProgramiv(program_object, GL_LINK_STATUS, &linked);
143
144  if (!linked) {
145    glDeleteProgram(program_object);
146    return 0;
147  }
148
149  return program_object;
150}
151
152class ESMatrix {
153 public:
154  GLfloat m[4][4];
155
156  ESMatrix() {
157    LoadZero();
158  }
159
160  void LoadZero() {
161    memset(this, 0x0, sizeof(ESMatrix));
162  }
163
164  void LoadIdentity() {
165    LoadZero();
166    m[0][0] = 1.0f;
167    m[1][1] = 1.0f;
168    m[2][2] = 1.0f;
169    m[3][3] = 1.0f;
170  }
171
172  void Multiply(ESMatrix* a, ESMatrix* b) {
173    ESMatrix result;
174    for (int i = 0; i < 4; ++i) {
175      result.m[i][0] = (a->m[i][0] * b->m[0][0]) +
176                       (a->m[i][1] * b->m[1][0]) +
177                       (a->m[i][2] * b->m[2][0]) +
178                       (a->m[i][3] * b->m[3][0]);
179
180      result.m[i][1] = (a->m[i][0] * b->m[0][1]) +
181                       (a->m[i][1] * b->m[1][1]) +
182                       (a->m[i][2] * b->m[2][1]) +
183                       (a->m[i][3] * b->m[3][1]);
184
185      result.m[i][2] = (a->m[i][0] * b->m[0][2]) +
186                       (a->m[i][1] * b->m[1][2]) +
187                       (a->m[i][2] * b->m[2][2]) +
188                       (a->m[i][3] * b->m[3][2]);
189
190      result.m[i][3] = (a->m[i][0] * b->m[0][3]) +
191                       (a->m[i][1] * b->m[1][3]) +
192                       (a->m[i][2] * b->m[2][3]) +
193                       (a->m[i][3] * b->m[3][3]);
194    }
195    *this = result;
196  }
197
198  void Frustum(float left,
199               float right,
200               float bottom,
201               float top,
202               float near_z,
203               float far_z) {
204    float delta_x = right - left;
205    float delta_y = top - bottom;
206    float delta_z = far_z - near_z;
207
208    if ((near_z <= 0.0f) ||
209        (far_z <= 0.0f) ||
210        (delta_z <= 0.0f) ||
211        (delta_y <= 0.0f) ||
212        (delta_y <= 0.0f))
213      return;
214
215    ESMatrix frust;
216    frust.m[0][0] = 2.0f * near_z / delta_x;
217    frust.m[0][1] = frust.m[0][2] = frust.m[0][3] = 0.0f;
218
219    frust.m[1][1] = 2.0f * near_z / delta_y;
220    frust.m[1][0] = frust.m[1][2] = frust.m[1][3] = 0.0f;
221
222    frust.m[2][0] = (right + left) / delta_x;
223    frust.m[2][1] = (top + bottom) / delta_y;
224    frust.m[2][2] = -(near_z + far_z) / delta_z;
225    frust.m[2][3] = -1.0f;
226
227    frust.m[3][2] = -2.0f * near_z * far_z / delta_z;
228    frust.m[3][0] = frust.m[3][1] = frust.m[3][3] = 0.0f;
229
230    Multiply(&frust, this);
231  }
232
233  void Perspective(float fov_y, float aspect, float near_z, float far_z) {
234    GLfloat frustum_h = tanf(fov_y / 360.0f * kPi) * near_z;
235    GLfloat frustum_w = frustum_h * aspect;
236    Frustum(-frustum_w, frustum_w, -frustum_h, frustum_h, near_z, far_z);
237  }
238
239  void Translate(GLfloat tx, GLfloat ty, GLfloat tz) {
240    m[3][0] += m[0][0] * tx + m[1][0] * ty + m[2][0] * tz;
241    m[3][1] += m[0][1] * tx + m[1][1] * ty + m[2][1] * tz;
242    m[3][2] += m[0][2] * tx + m[1][2] * ty + m[2][2] * tz;
243    m[3][3] += m[0][3] * tx + m[1][3] * ty + m[2][3] * tz;
244  }
245
246  void Rotate(GLfloat angle, GLfloat x, GLfloat y, GLfloat z) {
247    GLfloat mag = sqrtf(x * x + y * y + z * z);
248
249    GLfloat sin_angle = sinf(angle * kPi / 180.0f);
250    GLfloat cos_angle = cosf(angle * kPi / 180.0f);
251    if (mag > 0.0f) {
252      GLfloat xx, yy, zz, xy, yz, zx, xs, ys, zs;
253      GLfloat one_minus_cos;
254      ESMatrix rotation;
255
256      x /= mag;
257      y /= mag;
258      z /= mag;
259
260      xx = x * x;
261      yy = y * y;
262      zz = z * z;
263      xy = x * y;
264      yz = y * z;
265      zx = z * x;
266      xs = x * sin_angle;
267      ys = y * sin_angle;
268      zs = z * sin_angle;
269      one_minus_cos = 1.0f - cos_angle;
270
271      rotation.m[0][0] = (one_minus_cos * xx) + cos_angle;
272      rotation.m[0][1] = (one_minus_cos * xy) - zs;
273      rotation.m[0][2] = (one_minus_cos * zx) + ys;
274      rotation.m[0][3] = 0.0F;
275
276      rotation.m[1][0] = (one_minus_cos * xy) + zs;
277      rotation.m[1][1] = (one_minus_cos * yy) + cos_angle;
278      rotation.m[1][2] = (one_minus_cos * yz) - xs;
279      rotation.m[1][3] = 0.0F;
280
281      rotation.m[2][0] = (one_minus_cos * zx) - ys;
282      rotation.m[2][1] = (one_minus_cos * yz) + xs;
283      rotation.m[2][2] = (one_minus_cos * zz) + cos_angle;
284      rotation.m[2][3] = 0.0F;
285
286      rotation.m[3][0] = 0.0F;
287      rotation.m[3][1] = 0.0F;
288      rotation.m[3][2] = 0.0F;
289      rotation.m[3][3] = 1.0F;
290
291      Multiply(&rotation, this);
292    }
293  }
294};
295
296float RotationForTimeDelta(float delta_time) {
297  return delta_time * 40.0f;
298}
299
300float RotationForDragDistance(float drag_distance) {
301  return drag_distance / 5; // Arbitrary damping.
302}
303
304}  // namespace
305
306class SpinningCube::GLState {
307 public:
308  GLState();
309
310  void OnGLContextLost();
311
312  GLfloat angle_;  // Survives losing the GL context.
313
314  GLuint program_object_;
315  GLint position_location_;
316  GLint mvp_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  vbo_vertices_ = 0;
333  vbo_indices_ = 0;
334  num_indices_ = 0;
335}
336
337SpinningCube::SpinningCube()
338    : initialized_(false),
339      width_(0),
340      height_(0),
341      state_(new GLState()),
342      fling_multiplier_(1.0f),
343      direction_(1) {
344  state_->angle_ = 45.0f;
345}
346
347SpinningCube::~SpinningCube() {
348  if (!initialized_)
349    return;
350  if (state_->vbo_vertices_)
351    glDeleteBuffers(1, &state_->vbo_vertices_);
352  if (state_->vbo_indices_)
353    glDeleteBuffers(1, &state_->vbo_indices_);
354  if (state_->program_object_)
355    glDeleteProgram(state_->program_object_);
356}
357
358void SpinningCube::Init(uint32_t width, uint32_t height) {
359  width_ = width;
360  height_ = height;
361
362  const char vertext_shader_source[] =
363      "uniform mat4 u_mvpMatrix;                   \n"
364      "attribute vec4 a_position;                  \n"
365      "void main()                                 \n"
366      "{                                           \n"
367      "   gl_Position = u_mvpMatrix * a_position;  \n"
368      "}                                           \n";
369
370  const char fragment_shader_source[] =
371      "precision mediump float;                            \n"
372      "void main()                                         \n"
373      "{                                                   \n"
374      "  gl_FragColor = vec4( 0.0, 1.0, 0.0, 1.0 );        \n"
375      "}                                                   \n";
376
377  state_->program_object_ = LoadProgram(
378      vertext_shader_source, fragment_shader_source);
379  state_->position_location_ = glGetAttribLocation(
380      state_->program_object_, "a_position");
381  state_->mvp_location_ = glGetUniformLocation(
382      state_->program_object_, "u_mvpMatrix");
383  state_->num_indices_ = GenerateCube(
384      &state_->vbo_vertices_, &state_->vbo_indices_);
385
386  glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
387  initialized_ = true;
388}
389
390void SpinningCube::OnGLContextLost() {
391  initialized_ = false;
392  height_ = 0;
393  width_ = 0;
394  state_->OnGLContextLost();
395}
396
397void SpinningCube::SetFlingMultiplier(float drag_distance,
398                                      float drag_time) {
399  fling_multiplier_ = RotationForDragDistance(drag_distance) /
400      RotationForTimeDelta(drag_time);
401
402}
403
404void SpinningCube::UpdateForTimeDelta(float delta_time) {
405  state_->angle_ += RotationForTimeDelta(delta_time) * fling_multiplier_;
406  if (state_->angle_ >= 360.0f)
407    state_->angle_ -= 360.0f;
408
409  // Arbitrary 50-step linear reduction in spin speed.
410  if (fling_multiplier_ > 1.0f) {
411    fling_multiplier_ =
412        std::max(1.0f, fling_multiplier_ - (fling_multiplier_ - 1.0f) / 50);
413  }
414
415  Update();
416}
417
418void SpinningCube::UpdateForDragDistance(float distance) {
419  state_->angle_ += RotationForDragDistance(distance);
420  if (state_->angle_ >= 360.0f )
421    state_->angle_ -= 360.0f;
422
423  Update();
424}
425
426void SpinningCube::Draw() {
427  glViewport(0, 0, width_, height_);
428  glClear(GL_COLOR_BUFFER_BIT);
429  glUseProgram(state_->program_object_);
430  glBindBuffer(GL_ARRAY_BUFFER, state_->vbo_vertices_);
431  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, state_->vbo_indices_);
432  glVertexAttribPointer(state_->position_location_,
433                           3,
434                           GL_FLOAT,
435                           GL_FALSE, 3 * sizeof(GLfloat),
436                           0);
437  glEnableVertexAttribArray(state_->position_location_);
438  glUniformMatrix4fv(state_->mvp_location_,
439                        1,
440                        GL_FALSE,
441                        (GLfloat*) &state_->mvp_matrix_.m[0][0]);
442  glDrawElements(GL_TRIANGLES,
443                    state_->num_indices_,
444                    GL_UNSIGNED_SHORT,
445                    0);
446}
447
448void SpinningCube::Update() {
449  float aspect = static_cast<GLfloat>(width_) / static_cast<GLfloat>(height_);
450
451  ESMatrix perspective;
452  perspective.LoadIdentity();
453  perspective.Perspective(60.0f, aspect, 1.0f, 20.0f );
454
455  ESMatrix modelview;
456  modelview.LoadIdentity();
457  modelview.Translate(0.0, 0.0, -2.0);
458  modelview.Rotate(state_->angle_ * direction_, 1.0, 0.0, 1.0);
459
460  state_->mvp_matrix_.Multiply(&modelview, &perspective);
461}
462
463}  // namespace examples
464}  // namespace mojo
465