glGenFramebuffers example c c++ java objc

Name

glGenFramebuffers — generate framebuffer object names

C Specification

void glGenFramebuffers(	GLsizei	n,
	GLuint *	ids);

Parameters

n

Specifies the number of framebuffer object names to generate.

ids

Specifies an array in which the generated framebuffer object names are stored.

Description

glGenFramebuffers returns n framebuffer object names in ids. There is no guarantee that the names form a contiguous set of integers; however, it is guaranteed that none of the returned names was in use immediately before the call to glGenFramebuffers.
Framebuffer object names returned by a call to glGenFramebuffers are not returned by subsequent calls, unless they are first deleted with glDeleteFramebuffers.
The names returned in ids are marked as used, for the purposes of glGenFramebuffers only, but they acquire state and type only when they are first bound.

Errors

GL_INVALID_VALUE is generated if n is negative.

See Also

glBindFramebuffer, glDeleteFramebuffers

Copyright

Copyright © 2010 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.

Example of glGenFramebuffers

// This function does any needed initialization on the rendering
// context. 
void SetupRC()
{
    fprintf(stdout, "FBO Draw Buffers Demo\n\n");


    // Make sure required functionality is available: cube maps, auto mip gen, etc.
    if (!GLEE_VERSION_1_4)
    {
        fprintf(stderr, "OpenGL 1.4 is not available!\n");
        Sleep(2000);
        exit(0);
    }


    if (GLEE_ARB_texture_non_power_of_two)
    {
        npotTexturesAvailable = GL_TRUE;
    }
    else
    {
        fprintf(stderr, "GL_ARB_texture_non_power_of_two extension is not available!\n");
        fprintf(stderr, "Framebuffer effects will be lower resolution (lower quality).\n\n");
    }


    if (!GLEE_EXT_framebuffer_object)
    {
        fprintf(stderr, "GL_EXT_framebuffer_object extension is unavailable!\n");
        Sleep(2000);
        exit(0);
    }


    // we'll use up to 4 render targets if they're available
    glGetIntegerv(GL_MAX_DRAW_BUFFERS, &maxDrawBuffers);
    glGetIntegerv(GL_MAX_COLOR_ATTACHMENTS_EXT, &maxColorAttachments);
    glGetIntegerv(GL_MAX_TEXTURE_IMAGE_UNITS, &maxTexUnits);
    maxDrawBuffers = (maxDrawBuffers > maxColorAttachments) ? maxColorAttachments : maxDrawBuffers;
    maxDrawBuffers = (maxDrawBuffers > (maxTexUnits-1)) ? (maxTexUnits-1) : maxDrawBuffers;
    maxDrawBuffers = (maxDrawBuffers > 4) ? 4 : maxDrawBuffers;
    if (((!GLEE_ARB_draw_buffers || !GLEE_ARB_fragment_shader || !GLEE_ARB_shader_objects) 
        && !GLEE_VERSION_2_0) || (maxDrawBuffers != 4))
    {
        fprintf(stderr, "Support for at least 4 draw buffers is unavailable!\n");
        Sleep(2000);
        exit(0);
    }


    glGetIntegerv(GL_MAX_TEXTURE_SIZE, &maxTexSize);
    glGetIntegerv(GL_MAX_RENDERBUFFER_SIZE_EXT, &maxRenderbufferSize);
    maxTexSize = (maxRenderbufferSize > maxTexSize) ? maxTexSize : maxRenderbufferSize;


    fprintf(stdout, "Controls:\n");
    fprintf(stdout, "\tRight-click for menu\n\n");
    fprintf(stdout, "\tx/X\t\tMove +/- in x direction\n");
    fprintf(stdout, "\ty/Y\t\tMove +/- in y direction\n");
    fprintf(stdout, "\tz/Z\t\tMove +/- in z direction\n\n");
    fprintf(stdout, "\td/D\t\tToggle use of draw buffers\n\n");
    fprintf(stdout, "\tq\t\tExit demo\n\n");
    
    // Black background
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f );


    // Hidden surface removal
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);


    // Set up some lighting state that never changes
    glShadeModel(GL_SMOOTH);
    glLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER, 1);
    glLightfv(GL_LIGHT0, GL_AMBIENT, ambientLight);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuseLight);
    glLightfv(GL_LIGHT0, GL_SPECULAR, specularLight);
    glLightfv(GL_LIGHT0, GL_POSITION, lightPos);
    glMaterialfv(GL_FRONT, GL_SPECULAR, specularLight);
    glMateriali(GL_FRONT, GL_SHININESS, 128);
    glEnable(GL_LIGHTING);
    glEnable(GL_COLOR_MATERIAL);
    glEnable(GL_NORMALIZE);
    glEnable(GL_LIGHT0);


    // Set up textures & shaders
    SetupTextures();
    SetupShaders();


    // Set up some renderbuffer state
    glGenRenderbuffersEXT(1, &renderbufferID);
    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, renderbufferID);
    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT32, fboWidth, fboHeight);


    // glGenFramebuffers(2, framebufferID);
    glGenFramebuffersEXT(2, framebufferID);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, framebufferID[0]);
    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, renderbufferID);
    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, renderTextureID[0], 0);


    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, framebufferID[1]);
    for (int i = 0; i < maxDrawBuffers; i++)
    {
        glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT + i, GL_TEXTURE_2D, renderTextureID[i+1], 0);
    }
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
}