assignment1.cpp

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