framebuffer.cpp

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/*
 * Copyright (C) 2023  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Antkeeper source code is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#include <engine/gl/framebuffer.hpp>
#include <glad/gl.h>
#include <stdexcept>
 
namespace gl {
 
framebuffer::framebuffer(std::span<const framebuffer_attachment> attachments, std::uint32_t width, std::uint32_t height)
{
    m_dimensions = {width, height};
    m_attachments.assign(attachments.begin(), attachments.end());
    
    // Generate framebuffer
    glCreateFramebuffers(1, &m_gl_named_framebuffer);
    
    GLenum gl_color_attachment = GL_COLOR_ATTACHMENT0;
    std::vector<GLenum> gl_draw_buffers;
    
    // Attach textures to framebuffer
    for (const auto& attachment: m_attachments)
    {
        if (attachment.usage_mask & gl::color_attachment_bit)
        {
            glNamedFramebufferTexture
            (
                m_gl_named_framebuffer,
                gl_color_attachment,
                attachment.image_view->m_gl_texture_name,
                static_cast<GLuint>(attachment.level)
            );
            
            gl_draw_buffers.emplace_back(gl_color_attachment);
            ++gl_color_attachment;
        }
        
        if (attachment.usage_mask & gl::depth_attachment_bit)
        {
            if (attachment.usage_mask & gl::stencil_attachment_bit)
            {
                glNamedFramebufferTexture
                (
                    m_gl_named_framebuffer,
                    GL_DEPTH_STENCIL_ATTACHMENT,
                    attachment.image_view->m_gl_texture_name,
                    static_cast<GLuint>(attachment.level)
                );
            }
            else
            {
                glNamedFramebufferTexture
                (
                    m_gl_named_framebuffer,
                    GL_DEPTH_ATTACHMENT,
                    attachment.image_view->m_gl_texture_name,
                    static_cast<GLuint>(attachment.level)
                );
            }
        }
        else if (attachment.usage_mask & gl::stencil_attachment_bit)
        {
            glNamedFramebufferTexture
            (
                m_gl_named_framebuffer,
                GL_STENCIL_ATTACHMENT,
                attachment.image_view->m_gl_texture_name,
                static_cast<GLuint>(attachment.level)
            );
        }
    }
    
    // Specify read and draw buffers
    if (!gl_draw_buffers.empty())
    {
        glNamedFramebufferReadBuffer(m_gl_named_framebuffer, GL_COLOR_ATTACHMENT0);
        glNamedFramebufferDrawBuffers
        (
            m_gl_named_framebuffer,
            static_cast<GLsizei>(gl_draw_buffers.size()),
            gl_draw_buffers.data()
        );
    }
    else
    {
        glNamedFramebufferReadBuffer(m_gl_named_framebuffer, GL_NONE);
        glNamedFramebufferDrawBuffer(m_gl_named_framebuffer, GL_NONE);
    }
    
    if (glCheckNamedFramebufferStatus(m_gl_named_framebuffer, GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
    {
        throw std::runtime_error("OpenGL framebuffer incomplete.");
    }
}
 
framebuffer::~framebuffer()
{
    if (m_gl_named_framebuffer)
    {
        glDeleteFramebuffers(1, &m_gl_named_framebuffer);
    }
}
 
void framebuffer::resize(std::uint32_t width, std::uint32_t height)
{
    m_dimensions = {width, height};
}
 
} // namespace gl