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
  27
  28    if (!glutExtensionSupported("GL_EXT_framebuffer_object")) {
  29       printf("GL_EXT_framebuffer_object not found!\n");
  30       exit(0);
  31    }
  32
  33
  34    glGenFramebuffersEXT(1, &MyFB);
  35    glGenRenderbuffersEXT(1, &MyRB);
  36
  37    {
  38       glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB);
  39
  40       glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, MyRB);
  41
  42       glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT1_EXT,
  43                                    GL_RENDERBUFFER_EXT, MyRB);
  44
  45       glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
  46
  47       glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
  48    }
  49
  50 }
  51
  52
  53
  54 static void
  55 Reshape( int width, int height )
  56 {
  57    glViewport( 0, 0, width, height );
  58    glMatrixMode( GL_PROJECTION );
  59    glLoadIdentity();
  60    glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
  61    glMatrixMode( GL_MODELVIEW );
  62
  63    Width = width;
  64    Height = height;
  65    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
  66 }
  67
  68 static void Key(unsigned char key, int x, int y)
  69 {
  70
  71     switch (key) {
  72       case 27:
  73         exit(1);
  74       default:
  75         return;
  76     }
  77
  78     glutPostRedisplay();
  79 }
  80
  81
  82
  83 static void Draw( void )
  84 {
  85
  86    /* draw to user framebuffer */
  87    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB);
  88    glDrawBuffer(GL_COLOR_ATTACHMENT1_EXT);
  89    glReadBuffer(GL_COLOR_ATTACHMENT1_EXT);
  90
  91
  92    glViewport(0, 0, Width, Height);
  93    CheckError();
  94
  95    glClearColor(0.5, 0.5, 1.0, 0.0);
  96    glClear(GL_COLOR_BUFFER_BIT);
  97    CheckError();
  98
  99    if (0) {
 100       glBegin(GL_TRIANGLES);
 101       glColor3f(0,0,.7);
 102       glVertex3f( 0.9, -0.9, -30.0);
 103       glColor3f(.8,0,0);
 104       glVertex3f( 0.9,  0.9, -30.0);
 105       glColor3f(0,.9,0);
 106       glVertex3f(-0.9,  0.0, -30.0);
 107       glEnd();
 108    }
 109
 110    {
 111       GLubyte *buffer = malloc(Width * Height * 4);
 112
 113       /* read from user framebuffer */
 114       glReadPixels(0, 0, Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
 115       CheckError();
 116
 117       /* draw to window */
 118       glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
 119       glViewport(0, 0, Width, Height);
 120
 121       /* Try to clear the window, but will overwrite:
 122        */
 123       glClearColor(0.8, 0.8, 0, 0.0);
 124       glClear(GL_COLOR_BUFFER_BIT);
 125
 126       glWindowPos2iARB(30, 30);
 127       glDrawPixels(Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
 128
 129       free(buffer);
 130    }
 131
 132    /* Bind normal framebuffer */
 133    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
 134    glViewport(0, 0, Width, Height);
 135
 136    if (0) {
 137       glBegin(GL_TRIANGLES);
 138       glColor3f(0,.7,0);
 139       glVertex3f( 0.5, -0.5, -30.0);
 140       glColor3f(0,0,.8);
 141       glVertex3f( 0.5,  0.5, -30.0);
 142       glColor3f(.9,0,0);
 143       glVertex3f(-0.5,  0.0, -30.0);
 144       glEnd();
 145    }
 146
 147    if (doubleBuffer)
 148       glutSwapBuffers();
 149    else
 150       glFinish();
 151
 152    CheckError();
 153 }
 154
 155
 156 static GLenum Args(int argc, char **argv)
 157 {
 158     GLint i;
 159
 160     doubleBuffer = GL_FALSE;
 161
 162     for (i = 1; i < argc; i++) {
 163         if (strcmp(argv[i], "-sb") == 0) {
 164             doubleBuffer = GL_FALSE;
 165         } else if (strcmp(argv[i], "-db") == 0) {
 166             doubleBuffer = GL_TRUE;
 167         } else {
 168             fprintf(stderr, "%s (Bad option).\n", argv[i]);
 169             return GL_FALSE;
 170         }
 171     }
 172     return GL_TRUE;
 173 }
 174
 175
 176
 177 int
 178 main( int argc, char *argv[] )
 179 {
 180     GLenum type;
 181
 182     glutInit(&argc, argv);
 183
 184     if (Args(argc, argv) == GL_FALSE) {
 185         exit(1);
 186     }
 187
 188     glutInitWindowPosition(100, 0); glutInitWindowSize( Width, Height );
 189
 190     type = GLUT_RGB;
 191     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 192     glutInitDisplayMode(type);
 193
 194     if (glutCreateWindow(argv[0]) == GL_FALSE) {
 195         exit(1);
 196     }
 197
 198     glewInit();
 199
 200     Init();
 201
 202     glutReshapeFunc(Reshape);
 203     glutKeyboardFunc(Key);
 204     glutDisplayFunc(Draw);
 205     glutMainLoop();
 206     return 0;
 207 }