progs/tests/drawbuffers.c

   1 /*
   2  * Test GL_ARB_draw_buffers, GL_EXT_framebuffer_object
   3  * and GLSL's gl_FragData[].
   4  *
   5  * Brian Paul
   6  * 11 March 2007
   7  */
   8
   9
  10 #include <assert.h>
  11 #include <stdio.h>
  12 #include <stdlib.h>
  13 #include <math.h>
  14 #include <GL/glew.h>
  15 #include <GL/glut.h>
  16 #include "extfuncs.h"
  17
  18 static int Win;
  19 static int Width = 400, Height = 400;
  20 static GLuint FBobject, RBobjects[3];
  21 static GLfloat Xrot = 0.0, Yrot = 0.0;
  22 static GLuint Program;
  23
  24
  25 static void
  26 CheckError(int line)
  27 {
  28    GLenum err = glGetError();
  29    if (err) {
  30       printf("GL Error 0x%x at line %d\n", (int) err, line);
  31    }
  32 }
  33
  34
  35 static void
  36 Display(void)
  37 {
  38    GLubyte *buffer = malloc(Width * Height * 4);
  39    static const GLenum buffers[2] = {
  40       GL_COLOR_ATTACHMENT0_EXT,
  41       GL_COLOR_ATTACHMENT1_EXT
  42    };
  43
  44    glUseProgram_func(Program);
  45
  46    glEnable(GL_DEPTH_TEST);
  47
  48    /* draw to user framebuffer */
  49    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, FBobject);
  50
  51    /* Clear color buffer 0 (blue) */
  52    glDrawBuffer(GL_COLOR_ATTACHMENT0_EXT);
  53    glClearColor(0.5, 0.5, 1.0, 0.0);
  54    glClear(GL_COLOR_BUFFER_BIT);
  55
  56    /* Clear color buffer 1 (1 - blue) */
  57    glDrawBuffer(GL_COLOR_ATTACHMENT1_EXT);
  58    glClearColor(0.5, 0.5, 0.0, 0.0);
  59    glClear(GL_COLOR_BUFFER_BIT);
  60
  61    glClear(GL_DEPTH_BUFFER_BIT);
  62
  63    /* draw to two buffers w/ fragment shader */
  64    glDrawBuffersARB(2, buffers);
  65
  66    glPushMatrix();
  67    glRotatef(Xrot, 1, 0, 0);
  68    glRotatef(Yrot, 0, 1, 0);
  69    glutSolidTorus(0.75, 2.0, 10, 20);
  70    glPopMatrix();
  71
  72    /* read from user framebuffer */
  73    /* left half = colorbuffer 0 */
  74    glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);
  75    glPixelStorei(GL_PACK_ROW_LENGTH, Width);
  76    glPixelStorei(GL_PACK_SKIP_PIXELS, 0);
  77    glReadPixels(0, 0, Width / 2, Height, GL_RGBA, GL_UNSIGNED_BYTE,
  78                 buffer);
  79
  80    /* right half = colorbuffer 1 */
  81    glReadBuffer(GL_COLOR_ATTACHMENT1_EXT);
  82    glPixelStorei(GL_PACK_SKIP_PIXELS, Width / 2);
  83    glReadPixels(Width / 2, 0, Width - Width / 2, Height,
  84                 GL_RGBA, GL_UNSIGNED_BYTE,
  85                 buffer);
  86
  87    /* draw to window */
  88    glUseProgram_func(0);
  89    glDisable(GL_DEPTH_TEST);
  90    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
  91    glWindowPos2iARB(0, 0);
  92    glDrawPixels(Width, Height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
  93
  94    free(buffer);
  95    glutSwapBuffers();
  96    CheckError(__LINE__);
  97 }
  98
  99
 100 static void
 101 Reshape(int width, int height)
 102 {
 103    float ar = (float) width / (float) height;
 104
 105    glViewport(0, 0, width, height);
 106    glMatrixMode(GL_PROJECTION);
 107    glLoadIdentity();
 108    glFrustum(-ar, ar, -1.0, 1.0, 5.0, 35.0);
 109    glMatrixMode(GL_MODELVIEW);
 110    glLoadIdentity();
 111    glTranslatef(0.0, 0.0, -20.0);
 112
 113    Width = width;
 114    Height = height;
 115
 116    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[0]);
 117    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
 118    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[1]);
 119    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
 120    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[2]);
 121    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT,
 122                             Width, Height);
 123 }
 124
 125
 126 static void
 127 CleanUp(void)
 128 {
 129    glDeleteFramebuffersEXT(1, &FBobject);
 130    glDeleteRenderbuffersEXT(3, RBobjects);
 131    glutDestroyWindow(Win);
 132    exit(0);
 133 }
 134
 135
 136 static void
 137 Key(unsigned char key, int x, int y)
 138 {
 139    (void) x;
 140    (void) y;
 141    switch (key) {
 142       case 'x':
 143          Xrot += 5.0;
 144          break;
 145       case 'y':
 146          Yrot += 5.0;
 147          break;
 148       case 27:
 149          CleanUp();
 150          break;
 151    }
 152    glutPostRedisplay();
 153 }
 154
 155
 156 static void
 157 CheckExtensions(void)
 158 {
 159    const char *version = (const char *) glGetString(GL_VERSION);
 160    GLint numBuf;
 161
 162    if (!glutExtensionSupported("GL_EXT_framebuffer_object")) {
 163       printf("Sorry, GL_EXT_framebuffer_object is required!\n");
 164       exit(1);
 165    }
 166    if (!glutExtensionSupported("GL_ARB_draw_buffers")) {
 167       printf("Sorry, GL_ARB_draw_buffers is required!\n");
 168       exit(1);
 169    }
 170    if (version[0] != '2') {
 171       printf("Sorry, OpenGL 2.0 is required!\n");
 172       exit(1);
 173    }
 174
 175    glGetIntegerv(GL_MAX_DRAW_BUFFERS_ARB, &numBuf);
 176    printf("GL_MAX_DRAW_BUFFERS_ARB = %d\n", numBuf);
 177    if (numBuf < 2) {
 178       printf("Sorry, GL_MAX_DRAW_BUFFERS_ARB needs to be >= 2\n");
 179       exit(1);
 180    }
 181
 182    printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
 183 }
 184
 185
 186 static void
 187 SetupRenderbuffers(void)
 188 {
 189    glGenFramebuffersEXT(1, &FBobject);
 190    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, FBobject);
 191
 192    glGenRenderbuffersEXT(3, RBobjects);
 193
 194    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[0]);
 195    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
 196
 197    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[1]);
 198    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
 199
 200    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, RBobjects[2]);
 201    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT,
 202                             Width, Height);
 203
 204    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
 205                                 GL_RENDERBUFFER_EXT, RBobjects[0]);
 206    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT1_EXT,
 207                                 GL_RENDERBUFFER_EXT, RBobjects[1]);
 208    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT,
 209                                 GL_RENDERBUFFER_EXT, RBobjects[2]);
 210
 211    CheckError(__LINE__);
 212 }
 213
 214
 215 static GLuint
 216 LoadAndCompileShader(GLenum target, const char *text)
 217 {
 218    GLint stat;
 219    GLuint shader = glCreateShader_func(target);
 220    glShaderSource_func(shader, 1, (const GLchar **) &text, NULL);
 221    glCompileShader_func(shader);
 222    glGetShaderiv_func(shader, GL_COMPILE_STATUS, &stat);
 223    if (!stat) {
 224       GLchar log[1000];
 225       GLsizei len;
 226       glGetShaderInfoLog_func(shader, 1000, &len, log);
 227       fprintf(stderr, "drawbuffers: problem compiling shader:\n%s\n", log);
 228       exit(1);
 229    }
 230    return shader;
 231 }
 232
 233
 234 static void
 235 CheckLink(GLuint prog)
 236 {
 237    GLint stat;
 238    glGetProgramiv_func(prog, GL_LINK_STATUS, &stat);
 239    if (!stat) {
 240       GLchar log[1000];
 241       GLsizei len;
 242       glGetProgramInfoLog_func(prog, 1000, &len, log);
 243       fprintf(stderr, "drawbuffers: shader link error:\n%s\n", log);
 244    }
 245 }
 246
 247
 248 static void
 249 SetupShaders(void)
 250 {
 251    /* second color output = 1 - first color */
 252    static const char *fragShaderText =
 253       "void main() {\n"
 254       "   gl_FragData[0] = gl_Color; \n"
 255       "   gl_FragData[1] = vec4(1.0) - gl_Color; \n"
 256       "}\n";
 257
 258    GLuint fragShader;
 259
 260    fragShader = LoadAndCompileShader(GL_FRAGMENT_SHADER, fragShaderText);
 261    Program = glCreateProgram_func();
 262
 263    glAttachShader_func(Program, fragShader);
 264    glLinkProgram_func(Program);
 265    CheckLink(Program);
 266    glUseProgram_func(Program);
 267 }
 268
 269
 270 static void
 271 SetupLighting(void)
 272 {
 273    static const GLfloat frontMat[4] = { 1.0, 0.5, 0.5, 1.0 };
 274    static const GLfloat backMat[4] = { 1.0, 0.5, 0.5, 1.0 };
 275
 276    glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, frontMat);
 277    glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, backMat);
 278    glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, 1);
 279    glEnable(GL_LIGHT0);
 280    glEnable(GL_LIGHTING);
 281 }
 282
 283
 284 static void
 285 Init(void)
 286 {
 287    CheckExtensions();
 288    GetExtensionFuncs();
 289    SetupRenderbuffers();
 290    SetupShaders();
 291    SetupLighting();
 292    glEnable(GL_DEPTH_TEST);
 293 }
 294
 295
 296 int
 297 main(int argc, char *argv[])
 298 {
 299    glutInit(&argc, argv);
 300    glutInitWindowPosition(0, 0);
 301    glutInitWindowSize(Width, Height);
 302    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
 303    Win = glutCreateWindow(argv[0]);
 304    glewInit();
 305    glutReshapeFunc(Reshape);
 306    glutKeyboardFunc(Key);
 307    glutDisplayFunc(Display);
 308    Init();
 309    glutMainLoop();
 310    return 0;
 311 }