initial

1 files changed, 403 insertions, 0 deletions

diff --git a/spinning_cube.c b/spinning_cube.c
new file mode 100644
index 0000000..4cadf01
--- /dev/null
+++ b/spinning_cube.c
@@ -0,0 +1,403 @@
+// Copyright 2014 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 "spinning_cube.h"
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
+#include <algorithm>
+#include "GLES2/gl2.h"
+
+namespace {
+
+const float kPi = 3.14159265359f;
+
+int GenerateCube(GLuint *vbo_vertices, GLuint *vbo_indices) {
+    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) {
+        glGenBuffers(1, vbo_vertices);
+        glBindBuffer(GL_ARRAY_BUFFER, *vbo_vertices);
+        glBufferData(GL_ARRAY_BUFFER,
+                                 sizeof(cube_vertices),
+                                 cube_vertices,
+                                 GL_STATIC_DRAW);
+        glBindBuffer(GL_ARRAY_BUFFER, 0);
+    }
+
+    if (vbo_indices) {
+        glGenBuffers(1, vbo_indices);
+        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, *vbo_indices);
+        glBufferData(GL_ELEMENT_ARRAY_BUFFER,
+                                 sizeof(cube_indices),
+                                 cube_indices,
+                                 GL_STATIC_DRAW);
+        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+    }
+
+    return num_indices;
+}
+
+GLuint LoadShader(GLenum type, const char* shader_source) {
+    GLuint shader = glCreateShader(type);
+    glShaderSource(shader, 1, &shader_source, NULL);
+    glCompileShader(shader);
+    GLint compiled = 0;
+    glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
+    if (!compiled) {
+        glDeleteShader(shader);
+        return 0;
+    }
+    return shader;
+}
+
+GLuint LoadProgram(const char* vertext_shader_source, const char* fragment_shader_source) {
+    GLuint vertex_shader = LoadShader(GL_VERTEX_SHADER,
+        vertext_shader_source);
+    if (!vertex_shader)
+        return 0;
+    GLuint fragment_shader = LoadShader(GL_FRAGMENT_SHADER,
+        fragment_shader_source);
+    if (!fragment_shader) {
+        glDeleteShader(vertex_shader);
+        return 0;
+    }
+    GLuint program_object = glCreateProgram();
+    glAttachShader(program_object, vertex_shader);
+    glAttachShader(program_object, fragment_shader);
+    glLinkProgram(program_object);
+    glDeleteShader(vertex_shader);
+    glDeleteShader(fragment_shader);
+    GLint linked = 0;
+    glGetProgramiv(program_object, GL_LINK_STATUS, &linked);
+    if (!linked) {
+        glDeleteProgram(program_object);
+        return 0;
+    }
+    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 * kPi) * 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 * kPi / 180.0f);
+        GLfloat cos_angle = cosf(angle * kPi / 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);
+        }
+    }
+};
+
+float RotationForTimeDelta(float delta_time) {
+    return delta_time * 40.0f;
+}
+
+float RotationForDragDistance(float drag_distance) {
+    return drag_distance / 5; // Arbitrary damping.
+}
+
+}    // namespace
+
+class SpinningCube::GLState {
+public:
+    GLState();
+    void OnGLContextLost();
+    GLfloat angle_;    // Survives losing the GL context.
+    GLuint program_object_;
+    GLint position_location_;
+    GLint mvp_location_;
+    GLuint vbo_vertices_;
+    GLuint vbo_indices_;
+    int num_indices_;
+    ESMatrix mvp_matrix_;
+};
+
+SpinningCube::GLState::GLState()
+        : angle_(0) {
+    OnGLContextLost();
+}
+
+void SpinningCube::GLState::OnGLContextLost() {
+    program_object_ = 0;
+    position_location_ = 0;
+    mvp_location_ = 0;
+    vbo_vertices_ = 0;
+    vbo_indices_ = 0;
+    num_indices_ = 0;
+}
+
+SpinningCube::SpinningCube()
+      : initialized_(false),
+        width_(0),
+        height_(0),
+        state_(new GLState()),
+        fling_multiplier_(1.0f),
+        direction_(1) {
+    state_->angle_ = 45.0f;
+}
+
+SpinningCube::~SpinningCube() {
+    if (!initialized_)
+        return;
+    if (state_->vbo_vertices_)
+        glDeleteBuffers(1, &state_->vbo_vertices_);
+    if (state_->vbo_indices_)
+        glDeleteBuffers(1, &state_->vbo_indices_);
+    if (state_->program_object_)
+        glDeleteProgram(state_->program_object_);
+    delete state_;
+}
+
+void SpinningCube::Init(uint32_t width, uint32_t height) {
+    width_ = width;
+    height_ = height;
+    if (!initialized_) {
+        initialized_ = true;
+        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, 0.0, 1.0, 1.0 );\n"
+                "}\n";
+        state_->program_object_ = LoadProgram(
+                vertext_shader_source, fragment_shader_source);
+        state_->position_location_ = glGetAttribLocation(
+                state_->program_object_, "a_position");
+        state_->mvp_location_ = glGetUniformLocation(
+                state_->program_object_, "u_mvpMatrix");
+        state_->num_indices_ = GenerateCube(
+                &state_->vbo_vertices_, &state_->vbo_indices_);
+        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+    }
+}
+
+void SpinningCube::OnGLContextLost() {
+    // TODO(yzshen): Is it correct that in this case we don't need to do cleanup
+    // for program and buffers?
+    initialized_ = false;
+    height_ = 0;
+    width_ = 0;
+    state_->OnGLContextLost();
+}
+
+void SpinningCube::SetFlingMultiplier(float drag_distance, float drag_time) {
+    fling_multiplier_ = RotationForDragDistance(drag_distance) / RotationForTimeDelta(drag_time);
+}
+
+void SpinningCube::UpdateForTimeDelta(float delta_time) {
+    state_->angle_ += RotationForTimeDelta(delta_time) * fling_multiplier_;
+    if (state_->angle_ >= 360.0f)
+        state_->angle_ -= 360.0f;
+    // Arbitrary 50-step linear reduction in spin speed.
+    if (fling_multiplier_ > 1.0f) {
+        fling_multiplier_ = std::max(1.0f, fling_multiplier_ - (fling_multiplier_ - 1.0f) / 50);
+    }
+    Update();
+}
+
+void SpinningCube::UpdateForDragDistance(float distance) {
+    state_->angle_ += RotationForDragDistance(distance);
+    if (state_->angle_ >= 360.0f )
+        state_->angle_ -= 360.0f;
+    Update();
+}
+
+void SpinningCube::Draw() {
+    glViewport(0, 0, width_, height_);
+    glClear(GL_COLOR_BUFFER_BIT);
+    glUseProgram(state_->program_object_);
+    glBindBuffer(GL_ARRAY_BUFFER, state_->vbo_vertices_);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, state_->vbo_indices_);
+    glVertexAttribPointer(state_->position_location_, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), 0);
+    glEnableVertexAttribArray(state_->position_location_);
+    glUniformMatrix4fv(state_->mvp_location_, 1, GL_FALSE, (GLfloat*) &state_->mvp_matrix_.m[0][0]);
+    glDrawElements(GL_TRIANGLES, state_->num_indices_, GL_UNSIGNED_SHORT, 0);
+}
+
+void SpinningCube::Update() {
+    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_ * direction_, 1.0, 0.0, 1.0);
+    state_->mvp_matrix_.Multiply(&modelview, &perspective);
+}