fbo.cpp

///////////////////////////////////////////////////////////////////////
// A slight encapsulation of a Frame Buffer Object (i'e' Render
// Target) and its associated texture.  When the FBO is "Bound", the
// output of the graphics pipeline is captured into the texture.  When
// it is "Unbound", the texture is available for use as any normal
// texture.
////////////////////////////////////////////////////////////////////////

#include <glbinding/gl/gl.h>
#include <glbinding/Binding.h>
using namespace gl;

#include "fbo.h"

void FBO::CreateFBO(const int w, const int h)
{
    width = w;
    height = h;

    glGenFramebuffersEXT(1, &fboID);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fboID);

    // Create a render buffer, and attach it to FBO's depth attachment
    unsigned int depthBuffer;
    glGenRenderbuffersEXT(1, &depthBuffer);
    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depthBuffer);
    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT,
                             width, height);
    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT,
                                 GL_RENDERBUFFER_EXT, depthBuffer);

    // Create a texture and attach FBO's color 0 attachment.  The
    // GL_RGBA32F and GL_RGBA constants set this texture to be 32 bit
    // floats for each of the 4 components.  Many other choices are
    // possible.
    glGenTextures(1, &textureID);
    glBindTexture(GL_TEXTURE_2D, textureID);
    glTexImage2D(GL_TEXTURE_2D, 0, (int)GL_RGBA32F, width, height, 0, GL_RGBA, GL_FLOAT, NULL);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, (int)GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, (int)GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, (int)GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, (int)GL_LINEAR);

    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
                              GL_TEXTURE_2D, textureID, 0);

    // Check for completeness/correctness
    int status = (int)glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
    if (status != int(GL_FRAMEBUFFER_COMPLETE_EXT))
        printf("FBO Error: %d\n", status);

    // Unbind the fbo until it's ready to be used
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
}

void FBO::BindFBO() { glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fboID); }
void FBO::UnbindFBO() { glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); }

void FBO::BindTexture(const int unit, const int programId, const std::string& name)
{
    glActiveTexture((gl::GLenum)((int)GL_TEXTURE0 + unit));
    glBindTexture(GL_TEXTURE_2D, textureID);
    int loc = glGetUniformLocation(programId, name.c_str());
    glUniform1i(loc, unit);
}

void FBO::UnbindTexture(const int unit)
{  
    glActiveTexture((gl::GLenum)((int)GL_TEXTURE0 + unit));
    glBindTexture(GL_TEXTURE_2D, 0);
}