assignment1.cpp

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <fstream>
   4 #include <sstream>
   5 #include <vector>
   6 #ifdef __APPLE__
   7 #include <GL/glew.h>
   8 #else
   9 #include <OpenGL/glew.h>
  10 #endif
  11 #include <GLUT/glut.h>
  12
  13 #pragma clang diagnostic ignored "-Wdeprecated-declarations"
  14
  15 using namespace std;
  16
  17 GLuint* vaos;
  18 GLuint* progIds;
  19
  20 void display() {
  21         glClear(GL_COLOR_BUFFER_BIT);
  22         for (int i = 0; i < 2; i++) {
  23                 glUseProgram(progIds[i]);
  24                 glBindVertexArray(vaos[i]);
  25                 glDrawArrays(GL_TRIANGLES, 0, 3);
  26         }
  27         glutSwapBuffers();
  28 }
  29
  30 void attachShader(GLuint progId, const char* filePath, GLenum type) {
  31         GLuint shader = glCreateShader(type);
  32
  33         if (!shader) {
  34                 fprintf(stderr, "error creating shader\n");
  35                 exit(1);
  36         }
  37
  38         ifstream file(filePath);
  39         stringstream buffer;
  40         buffer << file.rdbuf();
  41         const char* contents = buffer.str().c_str();
  42
  43         glShaderSource(shader, 1, (const GLchar**)&contents, NULL);
  44         glCompileShader(shader);
  45         GLint success;
  46         glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
  47         if (!success) {
  48                 GLchar log[1024];
  49                 glGetShaderInfoLog(shader, 1024, NULL, log);
  50                 fprintf(stderr, "error: %s\n", log);
  51                 exit(1);
  52         }
  53         glAttachShader(progId, shader);
  54 }
  55
  56 GLuint compileShaders(char* vertexShader, char* fragmentShader) {
  57         GLuint progId = glCreateProgram();
  58
  59         attachShader(progId, vertexShader, GL_VERTEX_SHADER);
  60         attachShader(progId, fragmentShader, GL_FRAGMENT_SHADER);
  61
  62         glLinkProgram(progId);
  63         GLint success = 0;
  64         glGetProgramiv(progId, GL_LINK_STATUS, &success);
  65         if (!success) {
  66                 GLchar log[1024];
  67                 glGetProgramInfoLog(progId, sizeof(log), NULL, log);
  68                 fprintf(stderr, "error linking: %s\n", log);
  69                 exit(1);
  70         }
  71
  72         return progId;
  73 }
  74
  75 #define BUFFER_OFFSET(i) ((char *)NULL + (i))
  76
  77 GLuint setupBuffers(GLfloat* vertices, GLuint progId) {
  78
  79         GLfloat colors[] = {
  80                 0, 1, 0, 1,
  81                 1, 0, 0, 1,
  82                 0, 0, 1, 1
  83         };
  84
  85         GLuint numVerts = 3;
  86
  87         GLuint vbo;
  88         glGenBuffers(1, &vbo);
  89
  90         GLuint vao;
  91         glGenVertexArrays(1, &vao);
  92
  93         GLuint posId = glGetAttribLocation(progId, "vPosition");
  94         GLuint colorId = glGetAttribLocation(progId, "vColor");
  95
  96         GLuint vertsLen = numVerts * 3 * sizeof(GLfloat);
  97         GLuint colorsLen = numVerts * 4 * sizeof(GLfloat);
  98
  99         glBindBuffer(GL_ARRAY_BUFFER, vbo);
 100         glBufferData(GL_ARRAY_BUFFER, vertsLen + colorsLen, NULL, GL_STATIC_DRAW);
 101
 102         glBufferSubData(GL_ARRAY_BUFFER, 0, vertsLen, vertices);
 103         glBufferSubData(GL_ARRAY_BUFFER, vertsLen, colorsLen, colors);
 104
 105         glBindVertexArray(vao);
 106
 107         glEnableVertexAttribArray(posId);
 108         glEnableVertexAttribArray(colorId);
 109
 110         glVertexAttribPointer(posId, 3, GL_FLOAT, GL_FALSE, 0, 0);
 111         glVertexAttribPointer(colorId, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(numVerts * 3 * sizeof(GLfloat)));
 112
 113         return vao;
 114 }
 115
 116 void validateProgram(GLuint progId) {
 117         glValidateProgram(progId);
 118
 119         GLint success;
 120         glGetProgramiv(progId, GL_VALIDATE_STATUS, &success);
 121         if (!success) {
 122                 GLchar log[1024];
 123                 glGetProgramInfoLog(progId, sizeof(log), NULL, log);
 124                 fprintf(stderr, "error: %s\n", log);
 125                 exit(1);
 126         }
 127 }
 128
 129 void init() {
 130         GLfloat vertices[2][9] = {
 131                 {
 132                         0.0f, -1.0f, 0.0f,
 133                         1.0f, -1.0f, 0.0f,
 134                         0.5f, 1.0f, 0.0f
 135                 },
 136
 137                 {
 138                         -1.0f, -1.0f, 0.0f,
 139                         0.0f, -1.0f, 0.0f,
 140                         -0.5f, 1.0f, 0.0f
 141                 }
 142         };
 143
 144         vaos = new GLuint[2];
 145         progIds = new GLuint[2];
 146
 147         GLuint progId1 = compileShaders((char*)"vertex.glsl", (char*)"fragment.glsl");
 148         vaos[0] = setupBuffers(vertices[0], progId1);
 149         progIds[0] = progId1;
 150         validateProgram(progId1);
 151
 152         GLuint progId2 = compileShaders((char*)"vertex.glsl", (char*)"yellow.glsl");
 153         vaos[1] = setupBuffers(vertices[1], progId2);
 154         progIds[1] = progId2;
 155         validateProgram(progId2);
 156 }
 157
 158 int main(int argc, char** argv) {
 159         glutInit(&argc, argv);
 160         glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_3_2_CORE_PROFILE);
 161         glutInitWindowSize(800, 600);
 162         glutCreateWindow("Hello Triangle");
 163         glutDisplayFunc(display);
 164
 165         glewInit();
 166
 167         init();
 168
 169         glutMainLoop();
 170
 171         return 0;
 172 }
 173