Framebuffer Object Extension Examples
Quick example, render_to_texture (2D)
//RGBA8 2D texture, 24 bit depth texture, 256x256 glGenTextures(1, &color_tex); glBindTexture(GL_TEXTURE_2D, color_tex); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); //NULL means reserve texture memory, but texels are undefined glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 256, 256, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL); //------------------------- glGenFramebuffersEXT(1, &fb); glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fb); //Attach 2D texture to this FBO glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, color_tex, 0); //------------------------- glGenRenderbuffersEXT(1, &depth_rb); glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT24, 256, 256); //------------------------- //Attach depth buffer to FBO glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, depth_rb); //------------------------- //Does the GPU support current FBO configuration? GLenum status; status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT); switch(status) { case GL_FRAMEBUFFER_COMPLETE_EXT: cout<<"good"; default: HANDLE_THE_ERROR; } //------------------------- //and now you can render to GL_TEXTURE_2D glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fb); glClearColor(0.0, 0.0, 0.0, 0.0); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //------------------------- glViewport(0, 0, 256, 256); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(0.0, 256.0, 0.0, 256.0, -1.0, 1.0); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); //------------------------- glDisable(GL_TEXTURE_2D); glDisable(GL_BLEND); glEnable(GL_DEPTH_TEST); //------------------------- glColor3f(1.0, 1.0, 0.0); glBegin(GL_TRIANGLES); glVertex2f(0.0, 0.0); glVertex2f(256.0, 0.0); glVertex2f(256.0 , 256.0); glEnd(); //------------------------- GLubyte pixels[4*4*4]; glReadPixels(0, 0, 4, 4, GL_BGRA, GL_UNSIGNED_BYTE, pixels); //pixels 0, 1, 2 should be white //pixel 4 should be black //---------------- //Bind 0, which means render to back buffer glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
Quick example, render_to_texture (Cubemap)
//RGBA8 Cubemap texture, 24 bit depth texture, 256x256
glGenTextures(1, &color_tex); glBindTexture(GL_TEXTURE_CUBE_MAP, color_tex); glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_NEAREST); //NULL means reserve texture memory, but texels are undefined glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X+0, 0, GL_RGBA8, 256, 256, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL); glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X+1, 0, GL_RGBA8, 256, 256, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL); glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X+2, 0, GL_RGBA8, 256, 256, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL); glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X+3, 0, GL_RGBA8, 256, 256, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL); glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X+4, 0, GL_RGBA8, 256, 256, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL); glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X+5, 0, GL_RGBA8, 256, 256, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL); //------------------------- glGenFramebuffersEXT(1, &fb); glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fb); //Attach one of the faces of the Cubemap texture to this FBO glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_CUBE_MAP_POSITIVE_X, color_tex, 0); //------------------------- glGenRenderbuffersEXT(1, &depth_rb); glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT24, 256, 256); //------------------------- //Attach depth buffer to FBO glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, depth_rb); //------------------------- //Does the GPU support current FBO configuration? GLenum status; status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT); switch(status) { case GL_FRAMEBUFFER_COMPLETE_EXT: cout<<"good"; default: HANDLE_THE_ERROR; } //------------------------- //and now you can render to GL_TEXTURE_CUBE_MAP_POSITIVE_X