progs/trivial/tri-fbo.c

   1
   2 #include <assert.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5 #include <math.h>
   6 #include <string.h>
   7
   8 #include <GL/glew.h>
   9 #include <GL/glut.h>
  10
  11
  12
  13 static int Width = 400, Height = 400;
  14 static GLuint MyFB, MyRB;
  15
  16
  17 #define CheckError() assert(glGetError() == 0)
  18
  19 GLenum doubleBuffer;
  20
  21 static void Init(void)
  22 {
  23    fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
  24    fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
  25    fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
  26    fflush(stderr);
  27
  28
  29    if (!glutExtensionSupported("GL_EXT_framebuffer_object")) {
  30       printf("GL_EXT_framebuffer_object not found!\n");
  31       exit(0);
  32    }
  33
  34
  35    glGenFramebuffersEXT(1, &MyFB);
  36    glGenRenderbuffersEXT(1, &MyRB);
  37
  38    {
  39       glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB);
  40
  41       glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, MyRB);
  42
  43       glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT1_EXT,
  44                                    GL_RENDERBUFFER_EXT, MyRB);
  45
  46       glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
  47
  48       glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
  49    }
  50
  51    glClearColor(0.0, 0.0, 1.0, 0.0);
  52 }
  53
  54
  55
  56 static void
  57 Reshape( int width, int height )
  58 {
  59    glViewport( 0, 0, width, height );
  60    glMatrixMode( GL_PROJECTION );
  61    glLoadIdentity();
  62    glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
  63    glMatrixMode( GL_MODELVIEW );
  64
  65    Width = width;
  66    Height = height;
  67    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
  68 }
  69
  70
  71 static void Key(unsigned char key, int x, int y)
  72 {
  73
  74     switch (key) {
  75       case 27:
  76         exit(1);
  77       default:
  78         break;
  79     }
  80
  81     glutPostRedisplay();
  82 }
  83
  84
  85
  86 static void Draw( void )
  87 {
  88
  89    /* draw to user framebuffer */
  90    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB);
  91    glDrawBuffer(GL_COLOR_ATTACHMENT1_EXT);
  92    glReadBuffer(GL_COLOR_ATTACHMENT1_EXT);
  93
  94    glClearColor(0.5, 0.5, 1.0, 0.0);
  95    glClear(GL_COLOR_BUFFER_BIT);
  96    CheckError();
  97
  98    glBegin(GL_TRIANGLES);
  99    glColor3f(0,0,.7);
 100    glVertex3f( 0.9, -0.9, -30.0);
 101    glColor3f(.8,0,0);
 102    glVertex3f( 0.9,  0.9, -30.0);
 103    glColor3f(0,.9,0);
 104    glVertex3f(-0.9,  0.0, -30.0);
 105    glEnd();
 106
 107
 108    {
 109       GLubyte *buffer = malloc(Width * Height * 4);
 110
 111       /* read from user framebuffer */
 112       glReadPixels(0, 0, Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
 113       CheckError();
 114
 115       /* draw to window */
 116       glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
 117       /* Try to clear the window, but will overwrite:
 118        */
 119       glClearColor(0.8, 0.8, 0, 0.0);
 120       glClear(GL_COLOR_BUFFER_BIT);
 121
 122       glWindowPos2iARB(30, 30);
 123       glDrawPixels(Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
 124
 125
 126       free(buffer);
 127    }
 128
 129    /* Bind normal framebuffer */
 130    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
 131
 132    if (1) {
 133       glBegin(GL_TRIANGLES);
 134       glColor3f(0,.7,0);
 135       glVertex3f( 0.5, -0.5, -30.0);
 136       glColor3f(0,0,.8);
 137       glVertex3f( 0.5,  0.5, -30.0);
 138       glColor3f(.9,0,0);
 139       glVertex3f(-0.5,  0.0, -30.0);
 140       glEnd();
 141    }
 142
 143    if (doubleBuffer)
 144       glutSwapBuffers();
 145    else
 146       glFinish();
 147
 148    CheckError();
 149 }
 150
 151
 152 static GLenum Args(int argc, char **argv)
 153 {
 154     GLint i;
 155
 156     doubleBuffer = GL_FALSE;
 157
 158     for (i = 1; i < argc; i++) {
 159         if (strcmp(argv[i], "-sb") == 0) {
 160             doubleBuffer = GL_FALSE;
 161         } else if (strcmp(argv[i], "-db") == 0) {
 162             doubleBuffer = GL_TRUE;
 163         } else {
 164             fprintf(stderr, "%s (Bad option).\n", argv[i]);
 165             return GL_FALSE;
 166         }
 167     }
 168     return GL_TRUE;
 169 }
 170
 171
 172
 173 int
 174 main( int argc, char *argv[] )
 175 {
 176     GLenum type;
 177
 178     glutInit(&argc, argv);
 179
 180     if (Args(argc, argv) == GL_FALSE) {
 181         exit(1);
 182     }
 183
 184     glutInitWindowPosition(100, 0); glutInitWindowSize( Width, Height );
 185
 186     type = GLUT_RGB;
 187     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 188     glutInitDisplayMode(type);
 189
 190     if (glutCreateWindow(argv[0]) == GL_FALSE) {
 191         exit(1);
 192     }
 193
 194     glewInit();
 195
 196     Init();
 197
 198     glutReshapeFunc(Reshape);
 199     glutKeyboardFunc(Key);
 200     glutDisplayFunc(Draw);
 201     glutMainLoop();
 202     return 0;
 203 }