2 * Test GL_ARB_draw_buffers, GL_EXT_framebuffer_object
3 * and GLSL's gl_FragData[].
10 #define GL_GLEXT_PROTOTYPES
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
;
28 GLenum err
= glGetError();
30 printf("GL Error 0x%x at line %d\n", (int) err
, line
);
38 GLubyte
*buffer
= malloc(Width
* Height
* 4);
39 static const GLenum buffers
[2] = {
40 GL_COLOR_ATTACHMENT0_EXT
,
41 GL_COLOR_ATTACHMENT1_EXT
44 glUseProgram_func(Program
);
46 /* draw to user framebuffer */
47 glBindFramebufferEXT(GL_FRAMEBUFFER_EXT
, FBobject
);
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
);
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
);
59 glClear(GL_DEPTH_BUFFER_BIT
);
61 /* draw to two buffers w/ fragment shader */
62 glDrawBuffersARB(2, buffers
);
65 glRotatef(Xrot
, 1, 0, 0);
66 glRotatef(Yrot
, 0, 1, 0);
67 glutSolidTorus(0.75, 2.0, 10, 20);
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
,
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);
83 glBindFramebufferEXT(GL_FRAMEBUFFER_EXT
, 0);
84 glWindowPos2iARB(0, 0);
85 glDrawPixels(Width
, Height
, GL_RGBA
, GL_UNSIGNED_BYTE
, buffer
);
94 Reshape(int width
, int height
)
96 float ar
= (float) width
/ (float) height
;
98 glViewport(0, 0, width
, height
);
99 glMatrixMode(GL_PROJECTION
);
101 glFrustum(-ar
, ar
, -1.0, 1.0, 5.0, 35.0);
102 glMatrixMode(GL_MODELVIEW
);
104 glTranslatef(0.0, 0.0, -20.0);
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
,
122 glDeleteFramebuffersEXT(1, &FBobject
);
123 glDeleteRenderbuffersEXT(3, RBobjects
);
124 glutDestroyWindow(Win
);
130 Key(unsigned char key
, int x
, int y
)
150 CheckExtensions(void)
152 const char *version
= (const char *) glGetString(GL_VERSION
);
155 if (!glutExtensionSupported("GL_EXT_framebuffer_object")) {
156 printf("Sorry, GL_EXT_framebuffer_object is required!\n");
159 if (!glutExtensionSupported("GL_ARB_draw_buffers")) {
160 printf("Sorry, GL_ARB_draw_buffers is required!\n");
163 if (version
[0] != '2') {
164 printf("Sorry, OpenGL 2.0 is required!\n");
168 glGetIntegerv(GL_MAX_DRAW_BUFFERS_ARB
, &numBuf
);
169 printf("GL_MAX_DRAW_BUFFERS_ARB = %d\n", numBuf
);
171 printf("Sorry, GL_MAX_DRAW_BUFFERS_ARB needs to be >= 2\n");
175 printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER
));
180 SetupRenderbuffers(void)
182 glGenFramebuffersEXT(1, &FBobject
);
183 glBindFramebufferEXT(GL_FRAMEBUFFER_EXT
, FBobject
);
185 glGenRenderbuffersEXT(3, RBobjects
);
187 glBindRenderbufferEXT(GL_RENDERBUFFER_EXT
, RBobjects
[0]);
188 glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT
, GL_RGB
, Width
, Height
);
190 glBindRenderbufferEXT(GL_RENDERBUFFER_EXT
, RBobjects
[1]);
191 glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT
, GL_RGB
, Width
, Height
);
193 glBindRenderbufferEXT(GL_RENDERBUFFER_EXT
, RBobjects
[2]);
194 glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT
, GL_DEPTH_COMPONENT
,
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]);
204 CheckError(__LINE__
);
209 LoadAndCompileShader(GLenum target
, const char *text
)
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
);
219 glGetShaderInfoLog_func(shader
, 1000, &len
, log
);
220 fprintf(stderr
, "drawbuffers: problem compiling shader:\n%s\n", log
);
228 CheckLink(GLuint prog
)
231 glGetProgramiv_func(prog
, GL_LINK_STATUS
, &stat
);
235 glGetProgramInfoLog_func(prog
, 1000, &len
, log
);
236 fprintf(stderr
, "drawbuffers: shader link error:\n%s\n", log
);
244 /* second color output = 1 - first color */
245 static const char *fragShaderText
=
247 " gl_FragData[0] = gl_Color; \n"
248 " gl_FragData[1] = vec4(1.0) - gl_Color; \n"
253 fragShader
= LoadAndCompileShader(GL_FRAGMENT_SHADER
, fragShaderText
);
254 Program
= glCreateProgram_func();
256 glAttachShader_func(Program
, fragShader
);
257 glLinkProgram_func(Program
);
259 glUseProgram_func(Program
);
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 };
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);
273 glEnable(GL_LIGHTING
);
282 SetupRenderbuffers();
285 glEnable(GL_DEPTH_TEST
);
290 main(int argc
, char *argv
[])
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
);