progs/trivial/clear-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 = 512, Height = 512;
  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 }
  52
  53
  54
  55 static void
  56 Reshape( int width, int height )
  57 {
  58    glViewport( 0, 0, width, height );
  59    glMatrixMode( GL_PROJECTION );
  60    glLoadIdentity();
  61    glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
  62    glMatrixMode( GL_MODELVIEW );
  63
  64    Width = width;
  65    Height = height;
  66    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
  67 }
  68
  69 static void Key(unsigned char key, int x, int y)
  70 {
  71
  72     switch (key) {
  73       case 27:
  74         exit(1);
  75       default:
  76         break;
  77     }
  78
  79     glutPostRedisplay();
  80 }
  81
  82
  83
  84 static void Draw( void )
  85 {
  86
  87    /* draw to user framebuffer */
  88    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB);
  89    glDrawBuffer(GL_COLOR_ATTACHMENT1_EXT);
  90    glReadBuffer(GL_COLOR_ATTACHMENT1_EXT);
  91
  92
  93    glViewport(0, 0, Width, Height);
  94    CheckError();
  95
  96    glClearColor(0.5, 0.5, 1.0, 0.0);
  97    glClear(GL_COLOR_BUFFER_BIT);
  98    CheckError();
  99
 100    if (0) {
 101       glBegin(GL_TRIANGLES);
 102       glColor3f(0,0,.7);
 103       glVertex3f( 0.9, -0.9, -30.0);
 104       glColor3f(.8,0,0);
 105       glVertex3f( 0.9,  0.9, -30.0);
 106       glColor3f(0,.9,0);
 107       glVertex3f(-0.9,  0.0, -30.0);
 108       glEnd();
 109    }
 110
 111    {
 112       GLubyte *buffer = malloc(Width * Height * 4);
 113
 114       /* read from user framebuffer */
 115       glReadPixels(0, 0, Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
 116       CheckError();
 117
 118       /* draw to window */
 119       glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
 120       glViewport(0, 0, Width, Height);
 121
 122       /* Try to clear the window, but will overwrite:
 123        */
 124       glClearColor(0.8, 0.8, 0, 0.0);
 125       glClear(GL_COLOR_BUFFER_BIT);
 126
 127       glWindowPos2iARB(30, 30);
 128       glDrawPixels(Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
 129
 130       free(buffer);
 131    }
 132
 133    /* Bind normal framebuffer */
 134    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
 135    glViewport(0, 0, Width, Height);
 136
 137    if (0) {
 138       glBegin(GL_TRIANGLES);
 139       glColor3f(0,.7,0);
 140       glVertex3f( 0.5, -0.5, -30.0);
 141       glColor3f(0,0,.8);
 142       glVertex3f( 0.5,  0.5, -30.0);
 143       glColor3f(.9,0,0);
 144       glVertex3f(-0.5,  0.0, -30.0);
 145       glEnd();
 146    }
 147
 148    if (doubleBuffer)
 149       glutSwapBuffers();
 150    else
 151       glFinish();
 152
 153    CheckError();
 154 }
 155
 156
 157 static GLenum Args(int argc, char **argv)
 158 {
 159     GLint i;
 160
 161     doubleBuffer = GL_FALSE;
 162
 163     for (i = 1; i < argc; i++) {
 164         if (strcmp(argv[i], "-sb") == 0) {
 165             doubleBuffer = GL_FALSE;
 166         } else if (strcmp(argv[i], "-db") == 0) {
 167             doubleBuffer = GL_TRUE;
 168         } else {
 169             fprintf(stderr, "%s (Bad option).\n", argv[i]);
 170             return GL_FALSE;
 171         }
 172     }
 173     return GL_TRUE;
 174 }
 175
 176
 177
 178 int
 179 main( int argc, char *argv[] )
 180 {
 181     GLenum type;
 182
 183     glutInit(&argc, argv);
 184
 185     if (Args(argc, argv) == GL_FALSE) {
 186         exit(1);
 187     }
 188
 189     glutInitWindowPosition(100, 0); glutInitWindowSize( Width, Height );
 190
 191     type = GLUT_RGB;
 192     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 193     glutInitDisplayMode(type);
 194
 195     if (glutCreateWindow(argv[0]) == GL_FALSE) {
 196         exit(1);
 197     }
 198
 199     glewInit();
 200
 201     Init();
 202
 203     glutReshapeFunc(Reshape);
 204     glutKeyboardFunc(Key);
 205     glutDisplayFunc(Draw);
 206     glutMainLoop();
 207     return 0;
 208 }