Add a SpinningCube to Mojo's sample_app

mojo/examples/sample_app/spinning_cube.cc

+// Copyright 2013 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.
+
+// This example program is based on Simple_VertexShader.c from:
+
+//
+// Book:      OpenGL(R) ES 2.0 Programming Guide
+// Authors:   Aaftab Munshi, Dan Ginsburg, Dave Shreiner
+// ISBN-10:   0321502795
+// ISBN-13:   9780321502797
+// Publisher: Addison-Wesley Professional
+// URLs:      http://safari.informit.com/9780321563835
+//            http://www.opengles-book.com
+//
+
+#include "mojo/examples/sample_app/spinning_cube.h"
+
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
+#include "gpu/command_buffer/client/gles2_interface.h"
+#include "mojo/public/system/core.h"
+#include "mojo/public/system/macros.h"
+
+namespace mojo {
+namespace examples {
+
+namespace {
+
+int GenerateCube(gpu::gles2::GLES2Interface* gl,
+                 GLuint *vbo_vertices,
+                 GLuint *vbo_indices) {
+  // const int num_vertices = 24;
+  const int num_indices = 36;
+
+  const GLfloat cube_vertices[] = {
+    -0.5f, -0.5f, -0.5f,
+    -0.5f, -0.5f,  0.5f,
+    0.5f, -0.5f,  0.5f,
+    0.5f, -0.5f, -0.5f,
+    -0.5f,  0.5f, -0.5f,
+    -0.5f,  0.5f,  0.5f,
+    0.5f,  0.5f,  0.5f,
+    0.5f,  0.5f, -0.5f,
+    -0.5f, -0.5f, -0.5f,
+    -0.5f,  0.5f, -0.5f,
+    0.5f,  0.5f, -0.5f,
+    0.5f, -0.5f, -0.5f,
+    -0.5f, -0.5f, 0.5f,
+    -0.5f,  0.5f, 0.5f,
+    0.5f,  0.5f, 0.5f,
+    0.5f, -0.5f, 0.5f,
+    -0.5f, -0.5f, -0.5f,
+    -0.5f, -0.5f,  0.5f,
+    -0.5f,  0.5f,  0.5f,
+    -0.5f,  0.5f, -0.5f,
+    0.5f, -0.5f, -0.5f,
+    0.5f, -0.5f,  0.5f,
+    0.5f,  0.5f,  0.5f,
+    0.5f,  0.5f, -0.5f,
+  };
+
+  const GLushort cube_indices[] = {
+    0, 2, 1,
+    0, 3, 2,
+    4, 5, 6,
+    4, 6, 7,
+    8, 9, 10,
+    8, 10, 11,
+    12, 15, 14,
+    12, 14, 13,
+    16, 17, 18,
+    16, 18, 19,
+    20, 23, 22,
+    20, 22, 21
+  };
+
+  if (vbo_vertices) {
+    gl->GenBuffers(1, vbo_vertices);
+    gl->BindBuffer(GL_ARRAY_BUFFER, *vbo_vertices);
+    gl->BufferData(
+      GL_ARRAY_BUFFER, sizeof(cube_vertices), cube_vertices, GL_STATIC_DRAW);
+    gl->BindBuffer(GL_ARRAY_BUFFER, 0);
+  }
+
+  if (vbo_indices) {
+    gl->GenBuffers(1, vbo_indices);
+    gl->BindBuffer(GL_ELEMENT_ARRAY_BUFFER, *vbo_indices);
+    gl->BufferData(
+        GL_ELEMENT_ARRAY_BUFFER, sizeof(cube_indices), cube_indices, GL_STATIC_DRAW);
+    gl->BindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+  }
+
+  return num_indices;
+}
+
+GLuint LoadShader(gpu::gles2::GLES2Interface* gl,
+                  GLenum type,
+                  const char* shader_source) {
+  GLuint shader = gl->CreateShader(type);
+  if (!shader) {
+    return 0;
+  }
+
+  gl->ShaderSource(shader, 1, &shader_source, NULL);
+  gl->CompileShader(shader);
+
+  GLint compiled = 0;
+  gl->GetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
+
+  if (!compiled) {
+    gl->DeleteShader(shader);
+    return 0;
+  }
+
+  return shader;
+}
+
+GLuint LoadProgram(gpu::gles2::GLES2Interface* gl,
+                   const char* vertext_shader_source,
+                   const char* fragment_shader_source) {
+  GLuint vertex_shader = LoadShader(gl,
+                                    GL_VERTEX_SHADER,
+                                    vertext_shader_source);
+  if (!vertex_shader)
+    return 0;
+
+  GLuint fragment_shader = LoadShader(gl,
+                                      GL_FRAGMENT_SHADER,
+                                      fragment_shader_source);
+  if (!fragment_shader) {
+    gl->DeleteShader(vertex_shader);
+    return 0;
+  }
+
+  GLuint program_object = gl->CreateProgram();
+  if (!program_object)
+    return 0;  // Why don't we need to delete the shaders?

[jamesr, 2013/11/06 01:42:45]

this looks copied from cc/output/program_binding.h. In cc, we enforce (via
dchecks) that the only situation where a program creation fails is if the
context is lost, in which case trying to delete things is futile anyway.

[abarth-chromium, 2013/11/06 02:25:10]

It's actually copied from Simple_VertexShader.c (although I added the comment).
Ok.  I'll replace this with a DCHECK.

+
+  gl->AttachShader(program_object, vertex_shader);
+  gl->AttachShader(program_object, fragment_shader);
+
+  gl->LinkProgram(program_object);
+
+  GLint linked = 0;
+  gl->GetProgramiv(program_object, GL_LINK_STATUS, &linked);
+
+  if (!linked) {
+    gl->DeleteProgram(program_object);
+    return 0;  // Why don't we need to delete the shaders?
+  }
+
+  gl->DeleteShader(vertex_shader);
+  gl->DeleteShader(fragment_shader);
+
+  return program_object;
+}
+
+class ESMatrix {
+ public:
+  GLfloat m[4][4];
+
+  ESMatrix() {
+    LoadZero();
+  }
+
+  void LoadZero() {
+    memset(this, 0x0, sizeof(ESMatrix));
+  }
+
+  void LoadIdentity() {
+    LoadZero();
+    m[0][0] = 1.0f;
+    m[1][1] = 1.0f;
+    m[2][2] = 1.0f;
+    m[3][3] = 1.0f;
+  }
+
+  void Multiply(ESMatrix* a, ESMatrix* b) {
+    ESMatrix result;
+    for (int i = 0; i < 4; ++i) {
+      result.m[i][0] = (a->m[i][0] * b->m[0][0]) +
+                       (a->m[i][1] * b->m[1][0]) +
+                       (a->m[i][2] * b->m[2][0]) +
+                       (a->m[i][3] * b->m[3][0]);
+
+      result.m[i][1] = (a->m[i][0] * b->m[0][1]) +
+                       (a->m[i][1] * b->m[1][1]) +
+                       (a->m[i][2] * b->m[2][1]) +
+                       (a->m[i][3] * b->m[3][1]);
+
+      result.m[i][2] = (a->m[i][0] * b->m[0][2]) +
+                       (a->m[i][1] * b->m[1][2]) +
+                       (a->m[i][2] * b->m[2][2]) +
+                       (a->m[i][3] * b->m[3][2]);
+
+      result.m[i][3] = (a->m[i][0] * b->m[0][3]) +
+                       (a->m[i][1] * b->m[1][3]) +
+                       (a->m[i][2] * b->m[2][3]) +
+                       (a->m[i][3] * b->m[3][3]);
+    }
+    *this = result;
+  }
+
+  void Frustum(float left,
+               float right,
+               float bottom,
+               float top,
+               float near_z,
+               float far_z) {
+    float delta_x = right - left;
+    float delta_y = top - bottom;
+    float delta_z = far_z - near_z;
+
+    if ((near_z <= 0.0f) ||
+        (far_z <= 0.0f) ||
+        (delta_z <= 0.0f) ||
+        (delta_y <= 0.0f) ||
+        (delta_y <= 0.0f))
+      return;
+
+    ESMatrix frust;
+    frust.m[0][0] = 2.0f * near_z / delta_x;
+    frust.m[0][1] = frust.m[0][2] = frust.m[0][3] = 0.0f;
+
+    frust.m[1][1] = 2.0f * near_z / delta_y;
+    frust.m[1][0] = frust.m[1][2] = frust.m[1][3] = 0.0f;
+
+    frust.m[2][0] = (right + left) / delta_x;
+    frust.m[2][1] = (top + bottom) / delta_y;
+    frust.m[2][2] = -(near_z + far_z) / delta_z;
+    frust.m[2][3] = -1.0f;
+
+    frust.m[3][2] = -2.0f * near_z * far_z / delta_z;
+    frust.m[3][0] = frust.m[3][1] = frust.m[3][3] = 0.0f;
+
+    Multiply(&frust, this);
+  }
+
+  void Perspective(float fov_y, float aspect, float near_z, float far_z) {
+    GLfloat frustum_h = tanf(fov_y / 360.0f * M_PI) * near_z;
+    GLfloat frustum_w = frustum_h * aspect;
+    Frustum(-frustum_w, frustum_w, -frustum_h, frustum_h, near_z, far_z);
+  }
+
+  void Translate(GLfloat tx, GLfloat ty, GLfloat tz) {
+    m[3][0] += m[0][0] * tx + m[1][0] * ty + m[2][0] * tz;
+    m[3][1] += m[0][1] * tx + m[1][1] * ty + m[2][1] * tz;
+    m[3][2] += m[0][2] * tx + m[1][2] * ty + m[2][2] * tz;
+    m[3][3] += m[0][3] * tx + m[1][3] * ty + m[2][3] * tz;
+  }
+
+  void Rotate(GLfloat angle, GLfloat x, GLfloat y, GLfloat z) {
+    GLfloat mag = sqrtf(x * x + y * y + z * z);
+
+    GLfloat sin_angle = sinf(angle * M_PI / 180.0f);
+    GLfloat cos_angle = cosf(angle * M_PI / 180.0f);
+    if (mag > 0.0f) {
+      GLfloat xx, yy, zz, xy, yz, zx, xs, ys, zs;
+      GLfloat one_minus_cos;
+      ESMatrix rotation;
+
+      x /= mag;
+      y /= mag;
+      z /= mag;
+
+      xx = x * x;
+      yy = y * y;
+      zz = z * z;
+      xy = x * y;
+      yz = y * z;
+      zx = z * x;
+      xs = x * sin_angle;
+      ys = y * sin_angle;
+      zs = z * sin_angle;
+      one_minus_cos = 1.0f - cos_angle;
+
+      rotation.m[0][0] = (one_minus_cos * xx) + cos_angle;
+      rotation.m[0][1] = (one_minus_cos * xy) - zs;
+      rotation.m[0][2] = (one_minus_cos * zx) + ys;
+      rotation.m[0][3] = 0.0F;
+
+      rotation.m[1][0] = (one_minus_cos * xy) + zs;
+      rotation.m[1][1] = (one_minus_cos * yy) + cos_angle;
+      rotation.m[1][2] = (one_minus_cos * yz) - xs;
+      rotation.m[1][3] = 0.0F;
+
+      rotation.m[2][0] = (one_minus_cos * zx) - ys;
+      rotation.m[2][1] = (one_minus_cos * yz) + xs;
+      rotation.m[2][2] = (one_minus_cos * zz) + cos_angle;
+      rotation.m[2][3] = 0.0F;
+
+      rotation.m[3][0] = 0.0F;
+      rotation.m[3][1] = 0.0F;
+      rotation.m[3][2] = 0.0F;
+      rotation.m[3][3] = 1.0F;
+
+      Multiply(&rotation, this);
+    }
+  }
+};
+
+}
+
+class SpinningCube::GLState {
+ public:
+  GLState();
+
+  GLuint program_object_;
+  GLint position_location_;
+  GLint mvp_location_;
+  GLuint vbo_vertices_;
+  GLuint vbo_indices_;
+  int num_indices_;
+  GLfloat angle_;
+  ESMatrix mvp_matrix_;
+};
+
+SpinningCube::GLState::GLState()
+    : program_object_(0),
+      position_location_(0),
+      mvp_location_(0),
+      vbo_vertices_(0),
+      vbo_indices_(0),
+      num_indices_(0),
+      angle_(0) {
+}
+
+SpinningCube::SpinningCube(gpu::gles2::GLES2Interface* gl,
+                               int width,
+                               int height)
+    : gl_(gl),
+      width_(width),
+      height_(height),
+      state_(new GLState()) {
+  Initialize();
+}
+
+SpinningCube::~SpinningCube() {
+  if (state_->vbo_vertices_)
+    gl_->DeleteBuffers(1, &state_->vbo_vertices_);
+  if (state_->vbo_indices_)
+    gl_->DeleteBuffers(1, &state_->vbo_indices_);
+  if (state_->program_object_)
+    gl_->DeleteProgram(state_->program_object_);
+}
+
+void SpinningCube::Initialize() {
+  const char vertext_shader_source[] =
+      "uniform mat4 u_mvpMatrix;                   \n"
+      "attribute vec4 a_position;                  \n"
+      "void main()                                 \n"
+      "{                                           \n"
+      "   gl_Position = u_mvpMatrix * a_position;  \n"
+      "}                                           \n";
+
+  const char fragment_shader_source[] =
+      "precision mediump float;                            \n"
+      "void main()                                         \n"
+      "{                                                   \n"
+      "  gl_FragColor = vec4( 0.0, 1.0, 0.0, 1.0 );        \n"
+      "}                                                   \n";
+
+  state_->program_object_ = LoadProgram(
+      gl_, vertext_shader_source, fragment_shader_source);
+  state_->position_location_ = gl_->GetAttribLocation(
+      state_->program_object_, "a_position");
+  state_->mvp_location_ = gl_->GetUniformLocation(
+      state_->program_object_, "u_mvpMatrix");
+  state_->num_indices_ = GenerateCube(
+      gl_, &state_->vbo_vertices_, &state_->vbo_indices_);
+
+  gl_->ClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+  state_->angle_ = 45.0f;
+}
+
+void SpinningCube::Update(float delta_time) {
+  state_->angle_ += ( delta_time * 40.0f );
+  if (state_->angle_ >= 360.0f )
+    state_->angle_ -= 360.0f;
+
+  float aspect = static_cast<GLfloat>(width_) / static_cast<GLfloat>(height_);
+
+  ESMatrix perspective;
+  perspective.LoadIdentity();
+  perspective.Perspective(60.0f, aspect, 1.0f, 20.0f );
+
+  ESMatrix modelview;
+  modelview.LoadIdentity();
+  modelview.Translate(0.0, 0.0, -2.0);
+  modelview.Rotate(state_->angle_, 1.0, 0.0, 1.0);
+
+  state_->mvp_matrix_.Multiply(&modelview, &perspective);
+}
+
+void SpinningCube::Draw() {
+  gl_->Viewport(0, 0, width_, height_);
+  gl_->Clear(GL_COLOR_BUFFER_BIT);
+  gl_->UseProgram(state_->program_object_);
+  gl_->BindBuffer(GL_ARRAY_BUFFER, state_->vbo_vertices_);
+  gl_->BindBuffer(GL_ELEMENT_ARRAY_BUFFER, state_->vbo_indices_);
+  gl_->VertexAttribPointer(state_->position_location_,
+                           3,
+                           GL_FLOAT,
+                           GL_FALSE, 3 * sizeof(GLfloat),
+                           0);
+  gl_->EnableVertexAttribArray(state_->position_location_);
+  gl_->UniformMatrix4fv(state_->mvp_location_,
+                        1,
+                        GL_FALSE,
+                        (GLfloat*) &state_->mvp_matrix_.m[0][0]);
+  gl_->DrawElements(GL_TRIANGLES,
+                    state_->num_indices_,
+                    GL_UNSIGNED_SHORT,
+                    0);
+  gl_->SwapBuffers();
+}
+
+}  // namespace examples
+}  // namespace mojo