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