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