Celestia

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// frambuffer.cpp
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//
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// Copyright (C) 2010-2020, the Celestia Development Team
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// Original version by Chris Laurel <claurel@gmail.com>
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License
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// as published by the Free Software Foundation; either version 2
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// of the License, or (at your option) any later version.
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#include "framebuffer.h"
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FramebufferObject::FramebufferObject(GLuint width, GLuint height, unsigned int attachments) :
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    m_width(width),
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    m_height(height),
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    m_colorTexId(0),
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    m_depthTexId(0),
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    m_fboId(0),
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    m_status(GL_FRAMEBUFFER_UNSUPPORTED)
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{
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    if (attachments != 0)
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    {
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        generateFbo(attachments);
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    }
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}
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FramebufferObject::FramebufferObject(FramebufferObject &&other) noexcept:
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    m_width(other.m_width),
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    m_height(other.m_height),
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    m_colorTexId(other.m_colorTexId),
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    m_depthTexId(other.m_depthTexId),
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    m_fboId(other.m_fboId),
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    m_status(other.m_status)
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{
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    other.m_fboId  = 0;
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    other.m_status = GL_FRAMEBUFFER_UNSUPPORTED;
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}
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FramebufferObject& FramebufferObject::operator=(FramebufferObject &&other) noexcept
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{
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    m_width        = other.m_width;
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    m_height       = other.m_height;
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    m_colorTexId   = other.m_colorTexId;
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    m_depthTexId   = other.m_depthTexId;
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    m_fboId        = other.m_fboId;
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    m_status       = other.m_status;
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    other.m_fboId  = 0;
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    other.m_status = GL_FRAMEBUFFER_UNSUPPORTED;
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    return *this;
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}
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FramebufferObject::~FramebufferObject()
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{
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    cleanup();
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}
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bool
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FramebufferObject::isValid() const
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{
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    return m_status == GL_FRAMEBUFFER_COMPLETE;
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}
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GLuint
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FramebufferObject::colorTexture() const
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{
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    return m_colorTexId;
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}
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GLuint
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FramebufferObject::depthTexture() const
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{
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    return m_depthTexId;
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}
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void
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FramebufferObject::generateColorTexture()
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{
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    // Create and bind the texture
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    glGenTextures(1, &m_colorTexId);
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    glBindTexture(GL_TEXTURE_2D, m_colorTexId);
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    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
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    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
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    // Clamp to edge
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    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
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    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
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    // Set the texture dimensions
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    // Do we need to set GL_DEPTH_COMPONENT24 here?
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#ifdef GL_ES
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    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, m_width, m_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
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#else
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    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, m_width, m_height, 0, GL_RGB, GL_UNSIGNED_BYTE, nullptr);
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#endif
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    // Unbind the texture
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    glBindTexture(GL_TEXTURE_2D, 0);
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}
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#ifdef GL_ES
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#define CEL_DEPTH_FORMAT GL_UNSIGNED_INT
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#else
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#define CEL_DEPTH_FORMAT GL_UNSIGNED_BYTE
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#endif
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void
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FramebufferObject::generateDepthTexture()
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{
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    // Create and bind the texture
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    glGenTextures(1, &m_depthTexId);
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    glBindTexture(GL_TEXTURE_2D, m_depthTexId);
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#ifndef GL_ES
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    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 0);
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    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
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#endif
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    // Only nearest sampling is appropriate for depth textures
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    // But we can use linear to decrease aliasing
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    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
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    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
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    // Clamp to edge
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    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
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    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
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    // Set the texture dimensions
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    // Do we need to set GL_DEPTH_COMPONENT24 here?
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    glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, m_width, m_height, 0, GL_DEPTH_COMPONENT, CEL_DEPTH_FORMAT, nullptr);
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    // Unbind the texture
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    glBindTexture(GL_TEXTURE_2D, 0);
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}
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void
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FramebufferObject::generateFbo(unsigned int attachments)
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{
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    // Create the FBO
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    glGenFramebuffers(1, &m_fboId);
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    GLint oldFboId;
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    glGetIntegerv(GL_FRAMEBUFFER_BINDING, &oldFboId);
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    glBindFramebuffer(GL_FRAMEBUFFER, m_fboId);
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#ifndef GL_ES
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    glReadBuffer(GL_NONE);
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#endif
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    if ((attachments & ColorAttachment) != 0)
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    {
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        generateColorTexture();
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        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_colorTexId, 0);
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        m_status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
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        if (m_status != GL_FRAMEBUFFER_COMPLETE)
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        {
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            glBindFramebuffer(GL_FRAMEBUFFER, oldFboId);
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            cleanup();
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            return;
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        }
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    }
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#ifndef GL_ES
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    else
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    {
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        // Depth-only rendering; no color buffer.
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        glDrawBuffer(GL_NONE);
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    }
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#endif
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    if ((attachments & DepthAttachment) != 0)
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    {
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        generateDepthTexture();
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        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, m_depthTexId, 0);
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        m_status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
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        if (m_status != GL_FRAMEBUFFER_COMPLETE)
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        {
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            glBindFramebuffer(GL_FRAMEBUFFER, oldFboId);
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            cleanup();
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            return;
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        }
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    }
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    else
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    {
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        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, 0, 0);
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    }
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    // Restore default frame buffer
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    glBindFramebuffer(GL_FRAMEBUFFER, oldFboId);
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}
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// Delete all GL objects associated with this framebuffer object
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void
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FramebufferObject::cleanup()
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{
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    if (m_fboId != 0)
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    {
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        glDeleteFramebuffers(1, &m_fboId);
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    }
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    if (m_colorTexId != 0)
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    {
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        glDeleteTextures(1, &m_colorTexId);
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    }
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    if (m_depthTexId != 0)
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    {
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        glDeleteTextures(1, &m_depthTexId);
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    }
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}
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bool
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FramebufferObject::bind()
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{
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    if (isValid())
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    {
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        glBindFramebuffer(GL_FRAMEBUFFER, m_fboId);
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        return true;
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    }
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    return false;
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}
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bool
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FramebufferObject::unbind(GLint oldfboId)
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{
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    glBindFramebuffer(GL_FRAMEBUFFER, oldfboId);
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    return true;
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}
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