progs/trivial/clear-fbo-tex.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 GLenum TexTarget = GL_TEXTURE_2D;
  14 static int TexWidth = 512, TexHeight = 512;
  15 static GLenum TexIntFormat = GL_RGBA; /* either GL_RGB or GL_RGBA */
  16
  17 static int Width = 512, Height = 512;
  18 static GLuint MyFB, TexObj;
  19
  20
  21 #define CheckError() assert(glGetError() == 0)
  22
  23 GLenum doubleBuffer;
  24
  25 static void Init(void)
  26 {
  27    fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
  28    fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
  29    fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
  30    fflush(stderr);
  31
  32
  33    if (!glutExtensionSupported("GL_EXT_framebuffer_object")) {
  34       printf("GL_EXT_framebuffer_object not found!\n");
  35       exit(0);
  36    }
  37
  38
  39    glGenFramebuffersEXT(1, &MyFB);
  40    glGenTextures(1, &TexObj);
  41
  42    /* Make texture object/image */
  43    glBindTexture(TexTarget, TexObj);
  44    glTexParameteri(TexTarget, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
  45    glTexParameteri(TexTarget, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  46    glTexParameteri(TexTarget, GL_TEXTURE_BASE_LEVEL, 0);
  47    glTexParameteri(TexTarget, GL_TEXTURE_MAX_LEVEL, 0);
  48
  49    glTexImage2D(TexTarget, 0, TexIntFormat, TexWidth, TexHeight, 0,
  50                 GL_RGBA, GL_UNSIGNED_BYTE, NULL);
  51
  52
  53    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
  54
  55
  56
  57    {
  58       glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB);
  59
  60       glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
  61                                 TexTarget, TexObj, 0);
  62
  63
  64       glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
  65    }
  66
  67 }
  68
  69
  70
  71 static void
  72 Reshape( int width, int height )
  73 {
  74    glViewport( 0, 0, width, height );
  75    glMatrixMode( GL_PROJECTION );
  76    glLoadIdentity();
  77    glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
  78    glMatrixMode( GL_MODELVIEW );
  79
  80    Width = width;
  81    Height = height;
  82 }
  83
  84 static void Key(unsigned char key, int x, int y)
  85 {
  86
  87     switch (key) {
  88       case 27:
  89         exit(1);
  90       default:
  91         break;
  92     }
  93
  94     glutPostRedisplay();
  95 }
  96
  97
  98
  99 static void Draw( void )
 100 {
 101
 102
 103    /* draw to texture image */
 104    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB);
 105    /* glDrawBuffer(GL_COLOR_ATTACHMENT1_EXT); */
 106    /* glReadBuffer(GL_COLOR_ATTACHMENT1_EXT); */
 107
 108
 109    glViewport(0, 0, TexWidth, TexHeight);
 110    CheckError();
 111
 112    glClearColor(0.5, 0.5, 1.0, 0.0);
 113    glClear(GL_COLOR_BUFFER_BIT);
 114    CheckError();
 115
 116    if (0) {
 117       glBegin(GL_TRIANGLES);
 118       glColor3f(0,0,.7);
 119       glVertex3f( 0.9, -0.9, -30.0);
 120       glColor3f(.8,0,0);
 121       glVertex3f( 0.9,  0.9, -30.0);
 122       glColor3f(0,.9,0);
 123       glVertex3f(-0.9,  0.0, -30.0);
 124       glEnd();
 125    }
 126
 127    {
 128       GLubyte *buffer = malloc(Width * Height * 4);
 129
 130       /* read from user framebuffer */
 131       glReadPixels(0, 0, Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
 132       CheckError();
 133
 134       /* draw to window */
 135       glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
 136       glViewport(0, 0, Width, Height);
 137
 138       /* Try to clear the window, but will overwrite:
 139        */
 140       glClearColor(0.8, 0.8, 0, 0.0);
 141       glClear(GL_COLOR_BUFFER_BIT);
 142
 143       glWindowPos2iARB(30, 30);
 144       glDrawPixels(Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
 145
 146       free(buffer);
 147    }
 148
 149    /* Bind normal framebuffer */
 150    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
 151    glViewport(0, 0, Width, Height);
 152
 153    if (0) {
 154       glBegin(GL_TRIANGLES);
 155       glColor3f(0,.7,0);
 156       glVertex3f( 0.5, -0.5, -30.0);
 157       glColor3f(0,0,.8);
 158       glVertex3f( 0.5,  0.5, -30.0);
 159       glColor3f(.9,0,0);
 160       glVertex3f(-0.5,  0.0, -30.0);
 161       glEnd();
 162    }
 163
 164    if (doubleBuffer) {
 165       glutSwapBuffers();
 166    }
 167
 168    CheckError();
 169 }
 170
 171
 172 static GLenum Args(int argc, char **argv)
 173 {
 174     GLint i;
 175
 176     doubleBuffer = GL_FALSE;
 177
 178     for (i = 1; i < argc; i++) {
 179         if (strcmp(argv[i], "-sb") == 0) {
 180             doubleBuffer = GL_FALSE;
 181         } else if (strcmp(argv[i], "-db") == 0) {
 182             doubleBuffer = GL_TRUE;
 183         } else {
 184             fprintf(stderr, "%s (Bad option).\n", argv[i]);
 185             return GL_FALSE;
 186         }
 187     }
 188     return GL_TRUE;
 189 }
 190
 191
 192
 193 int
 194 main( int argc, char *argv[] )
 195 {
 196     GLenum type;
 197
 198     glutInit(&argc, argv);
 199
 200     if (Args(argc, argv) == GL_FALSE) {
 201         exit(1);
 202     }
 203
 204     glutInitWindowPosition(100, 0); glutInitWindowSize( Width, Height );
 205
 206     type = GLUT_RGB;
 207     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 208     glutInitDisplayMode(type);
 209
 210     if (glutCreateWindow(argv[0]) == GL_FALSE) {
 211         exit(1);
 212     }
 213
 214     glewInit();
 215
 216     Init();
 217
 218     glutReshapeFunc(Reshape);
 219     glutKeyboardFunc(Key);
 220     glutDisplayFunc(Draw);
 221     glutMainLoop();
 222     return 0;
 223 }