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# glbuffers.cpp Example File
demos/boxes/glbuffers.cpp

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     #include "glbuffers.h"
     #include <QtGui/qmatrix4x4.h>

     //============================================================================//
     //                                  GLTexture                                 //
     //============================================================================//

     GLTexture::GLTexture() : m_texture(0), m_failed(false)
     {
         glGenTextures(1, &m_texture);
     }

     GLTexture::~GLTexture()
     {
         glDeleteTextures(1, &m_texture);
     }

     //============================================================================//
     //                                 GLTexture2D                                //
     //============================================================================//

     GLTexture2D::GLTexture2D(int width, int height)
     {
         glBindTexture(GL_TEXTURE_2D, m_texture);
         glTexImage2D(GL_TEXTURE_2D, 0, 4, width, height, 0,
             GL_BGRA, GL_UNSIGNED_BYTE, 0);

         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_MAG_FILTER, GL_LINEAR);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
         //glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
         //glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
         glBindTexture(GL_TEXTURE_2D, 0);
     }

     GLTexture2D::GLTexture2D(const QString& fileName, int width, int height)
     {
         // TODO: Add error handling.
         QImage image(fileName);

         if (image.isNull()) {
             m_failed = true;
             return;
         }

         image = image.convertToFormat(QImage::Format_ARGB32);

         //qDebug() << "Image size:" << image.width() << "x" << image.height();
         if (width <= 0)
             width = image.width();
         if (height <= 0)
             height = image.height();
         if (width != image.width() || height != image.height())
             image = image.scaled(width, height, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);

         glBindTexture(GL_TEXTURE_2D, m_texture);

         // Works on x86, so probably works on all little-endian systems.
         // Does it work on big-endian systems?
         glTexImage2D(GL_TEXTURE_2D, 0, 4, image.width(), image.height(), 0,
             GL_BGRA, GL_UNSIGNED_BYTE, image.bits());

         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_MAG_FILTER, GL_LINEAR);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
         //glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
         //glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
         glBindTexture(GL_TEXTURE_2D, 0);
     }

     void GLTexture2D::load(int width, int height, QRgb *data)
     {
         glBindTexture(GL_TEXTURE_2D, m_texture);
         glTexImage2D(GL_TEXTURE_2D, 0, 4, width, height, 0,
             GL_BGRA, GL_UNSIGNED_BYTE, data);
         glBindTexture(GL_TEXTURE_2D, 0);
     }

     void GLTexture2D::bind()
     {
         glBindTexture(GL_TEXTURE_2D, m_texture);
         glEnable(GL_TEXTURE_2D);
     }

     void GLTexture2D::unbind()
     {
         glBindTexture(GL_TEXTURE_2D, 0);
         glDisable(GL_TEXTURE_2D);
     }

     //============================================================================//
     //                                 GLTexture3D                                //
     //============================================================================//

     GLTexture3D::GLTexture3D(int width, int height, int depth)
     {
         GLBUFFERS_ASSERT_OPENGL("GLTexture3D::GLTexture3D", glTexImage3D, return)

         glBindTexture(GL_TEXTURE_3D, m_texture);
         glTexImage3D(GL_TEXTURE_3D, 0, 4, width, height, depth, 0,
             GL_BGRA, GL_UNSIGNED_BYTE, 0);

         glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_S, GL_REPEAT);
         glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_T, GL_REPEAT);
         glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_R, GL_REPEAT);
         glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
         glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
         //glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
         //glTexParameteri(GL_TEXTURE_3D, GL_GENERATE_MIPMAP, GL_TRUE);
         glBindTexture(GL_TEXTURE_3D, 0);
     }

     void GLTexture3D::load(int width, int height, int depth, QRgb *data)
     {
         GLBUFFERS_ASSERT_OPENGL("GLTexture3D::load", glTexImage3D, return)

         glBindTexture(GL_TEXTURE_3D, m_texture);
         glTexImage3D(GL_TEXTURE_3D, 0, 4, width, height, depth, 0,
             GL_BGRA, GL_UNSIGNED_BYTE, data);
         glBindTexture(GL_TEXTURE_3D, 0);
     }

     void GLTexture3D::bind()
     {
         glBindTexture(GL_TEXTURE_3D, m_texture);
         glEnable(GL_TEXTURE_3D);
     }

     void GLTexture3D::unbind()
     {
         glBindTexture(GL_TEXTURE_3D, 0);
         glDisable(GL_TEXTURE_3D);
     }

     //============================================================================//
     //                                GLTextureCube                               //
     //============================================================================//

     GLTextureCube::GLTextureCube(int size)
     {
         glBindTexture(GL_TEXTURE_CUBE_MAP, m_texture);

         for (int i = 0; i < 6; ++i)
             glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, 4, size, size, 0,
                 GL_BGRA, GL_UNSIGNED_BYTE, 0);

         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_MAG_FILTER, GL_LINEAR);
         glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
         //glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
         //glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_GENERATE_MIPMAP, GL_TRUE);
         glBindTexture(GL_TEXTURE_CUBE_MAP, 0);
     }

     GLTextureCube::GLTextureCube(const QStringList& fileNames, int size)
     {
         // TODO: Add error handling.

         glBindTexture(GL_TEXTURE_CUBE_MAP, m_texture);

         int index = 0;
         foreach (QString file, fileNames) {
             QImage image(file);
             if (image.isNull()) {
                 m_failed = true;
                 break;
             }

             image = image.convertToFormat(QImage::Format_ARGB32);

             //qDebug() << "Image size:" << image.width() << "x" << image.height();
             if (size <= 0)
                 size = image.width();
             if (size != image.width() || size != image.height())
                 image = image.scaled(size, size, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);

             // Works on x86, so probably works on all little-endian systems.
             // Does it work on big-endian systems?
             glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + index, 0, 4, image.width(), image.height(), 0,
                 GL_BGRA, GL_UNSIGNED_BYTE, image.bits());

             if (++index == 6)
                 break;
         }

         // Clear remaining faces.
         while (index < 6) {
             glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + index, 0, 4, size, size, 0,
                 GL_BGRA, GL_UNSIGNED_BYTE, 0);
             ++index;
         }

         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_MAG_FILTER, GL_LINEAR);
         glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
         //glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
         //glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_GENERATE_MIPMAP, GL_TRUE);
         glBindTexture(GL_TEXTURE_CUBE_MAP, 0);
     }

     void GLTextureCube::load(int size, int face, QRgb *data)
     {
         glBindTexture(GL_TEXTURE_CUBE_MAP, m_texture);
             glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, 0, 4, size, size, 0,
                 GL_BGRA, GL_UNSIGNED_BYTE, data);
         glBindTexture(GL_TEXTURE_CUBE_MAP, 0);
     }

     void GLTextureCube::bind()
     {
         glBindTexture(GL_TEXTURE_CUBE_MAP, m_texture);
         glEnable(GL_TEXTURE_CUBE_MAP);
     }

     void GLTextureCube::unbind()
     {
         glBindTexture(GL_TEXTURE_CUBE_MAP, 0);
         glDisable(GL_TEXTURE_CUBE_MAP);
     }

     //============================================================================//
     //                            GLFrameBufferObject                             //
     //============================================================================//

     GLFrameBufferObject::GLFrameBufferObject(int width, int height)
         : m_fbo(0)
         , m_depthBuffer(0)
         , m_width(width)
         , m_height(height)
         , m_failed(false)
     {
         GLBUFFERS_ASSERT_OPENGL("GLFrameBufferObject::GLFrameBufferObject",
             glGenFramebuffersEXT && glGenRenderbuffersEXT && glBindRenderbufferEXT && glRenderbufferStorageEXT, return)

         // TODO: share depth buffers of same size
         glGenFramebuffersEXT(1, &m_fbo);
         //glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, m_fbo);
         glGenRenderbuffersEXT(1, &m_depthBuffer);
         glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, m_depthBuffer);
         glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT, m_width, m_height);
         //glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, m_depthBuffer);
         //glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
     }

     GLFrameBufferObject::~GLFrameBufferObject()
     {
         GLBUFFERS_ASSERT_OPENGL("GLFrameBufferObject::~GLFrameBufferObject",
             glDeleteFramebuffersEXT && glDeleteRenderbuffersEXT, return)

         glDeleteFramebuffersEXT(1, &m_fbo);
         glDeleteRenderbuffersEXT(1, &m_depthBuffer);
     }

     void GLFrameBufferObject::setAsRenderTarget(bool state)
     {
         GLBUFFERS_ASSERT_OPENGL("GLFrameBufferObject::setAsRenderTarget", glBindFramebufferEXT, return)

         if (state) {
             glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, m_fbo);
             glPushAttrib(GL_VIEWPORT_BIT);
             glViewport(0, 0, m_width, m_height);
         } else {
             glPopAttrib();
             glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
         }
     }

     bool GLFrameBufferObject::isComplete()
     {
         GLBUFFERS_ASSERT_OPENGL("GLFrameBufferObject::isComplete", glCheckFramebufferStatusEXT, return false)

         return GL_FRAMEBUFFER_COMPLETE_EXT == glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
     }

     //============================================================================//
     //                             GLRenderTargetCube                             //
     //============================================================================//

     GLRenderTargetCube::GLRenderTargetCube(int size)
         : GLTextureCube(size)
         , m_fbo(size, size)
     {
     }

     void GLRenderTargetCube::begin(int face)
     {
         GLBUFFERS_ASSERT_OPENGL("GLRenderTargetCube::begin",
             glFramebufferTexture2DEXT && glFramebufferRenderbufferEXT, return)

         m_fbo.setAsRenderTarget(true);
         glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
             GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, m_texture, 0);
         glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, m_fbo.m_depthBuffer);
     }

     void GLRenderTargetCube::end()
     {
         m_fbo.setAsRenderTarget(false);
     }

     void GLRenderTargetCube::getViewMatrix(QMatrix4x4& mat, int face)
     {
         if (face < 0 || face >= 6) {
             qWarning("GLRenderTargetCube::getViewMatrix: 'face' must be in the range [0, 6). (face == %d)", face);
             return;
         }

         static int perm[6][3] = {
             {2, 1, 0},
             {2, 1, 0},
             {0, 2, 1},
             {0, 2, 1},
             {0, 1, 2},
             {0, 1, 2},
         };

         static float signs[6][3] = {
             {-1.0f, -1.0f, -1.0f},
             {+1.0f, -1.0f, +1.0f},
             {+1.0f, +1.0f, -1.0f},
             {+1.0f, -1.0f, +1.0f},
             {+1.0f, -1.0f, -1.0f},
             {-1.0f, -1.0f, +1.0f},
         };

         mat.fill(0.0f);
         for (int i = 0; i < 3; ++i)
             mat(i, perm[face][i]) = signs[face][i];
         mat(3, 3) = 1.0f;
     }

     void GLRenderTargetCube::getProjectionMatrix(QMatrix4x4& mat, float nearZ, float farZ)
     {
         static const QMatrix4x4 reference(
                 1.0f, 0.0f, 0.0f, 0.0f,
                 0.0f, 1.0f, 0.0f, 0.0f,
                 0.0f, 0.0f, 0.0f, 0.0f,
                 0.0f, 0.0f, -1.0f, 0.0f);

         mat = reference;
         mat(2, 2) = (nearZ+farZ)/(nearZ-farZ);
         mat(2, 3) = 2.0f*nearZ*farZ/(nearZ-farZ);
     }