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