glbuffers.h Example File
demos/boxes/glbuffers.h

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 #ifndef GLBUFFERS_H
 #define GLBUFFERS_H

 //#include <GL/glew.h>
 #include "glextensions.h"

 #include <QtGui>
 #include <QtOpenGL>

 #define BUFFER_OFFSET(i) ((char*)0 + (i))
 #define SIZE_OF_MEMBER(cls, member) sizeof(static_cast<cls *>(0)->member)

 #define GLBUFFERS_ASSERT_OPENGL(prefix, assertion, returnStatement)                         \
 if (m_failed || !(assertion)) {                                                             \
     if (!m_failed) qCritical(prefix ": The necessary OpenGL functions are not available."); \
     m_failed = true;                                                                        \
     returnStatement;                                                                        \
 }

 class QMatrix4x4;

 class GLTexture
 {
 public:
     GLTexture();
     virtual ~GLTexture();
     virtual void bind() = 0;
     virtual void unbind() = 0;
     virtual bool failed() const {return m_failed;}
 protected:
     GLuint m_texture;
     bool m_failed;
 };

 class GLFrameBufferObject
 {
 public:
     friend class GLRenderTargetCube;
     // friend class GLRenderTarget2D;

     GLFrameBufferObject(int width, int height);
     virtual ~GLFrameBufferObject();
     bool isComplete();
     virtual bool failed() const {return m_failed;}
 protected:
     void setAsRenderTarget(bool state = true);
     GLuint m_fbo;
     GLuint m_depthBuffer;
     int m_width, m_height;
     bool m_failed;
 };

 class GLTexture2D : public GLTexture
 {
 public:
     GLTexture2D(int width, int height);
     GLTexture2D(const QString& fileName, int width = 0, int height = 0);
     void load(int width, int height, QRgb *data);
     virtual void bind();
     virtual void unbind();
 };

 class GLTexture3D : public GLTexture
 {
 public:
     GLTexture3D(int width, int height, int depth);
     // TODO: Implement function below
     //GLTexture3D(const QString& fileName, int width = 0, int height = 0);
     void load(int width, int height, int depth, QRgb *data);
     virtual void bind();
     virtual void unbind();
 };

 class GLTextureCube : public GLTexture
 {
 public:
     GLTextureCube(int size);
     GLTextureCube(const QStringList& fileNames, int size = 0);
     void load(int size, int face, QRgb *data);
     virtual void bind();
     virtual void unbind();
 };

 // TODO: Define and implement class below
 //class GLRenderTarget2D : public GLTexture2D

 class GLRenderTargetCube : public GLTextureCube
 {
 public:
     GLRenderTargetCube(int size);
     // begin rendering to one of the cube's faces. 0 <= face < 6
     void begin(int face);
     // end rendering
     void end();
     virtual bool failed() {return m_failed || m_fbo.failed();}

     static void getViewMatrix(QMatrix4x4& mat, int face);
     static void getProjectionMatrix(QMatrix4x4& mat, float nearZ, float farZ);
 private:
     GLFrameBufferObject m_fbo;
 };

 struct VertexDescription
 {
     enum
     {
         Null = 0, // Terminates a VertexDescription array
         Position,
         TexCoord,
         Normal,
         Color,
     };
     int field; // Position, TexCoord, Normal, Color
     int type; // GL_FLOAT, GL_UNSIGNED_BYTE
     int count; // number of elements
     int offset; // field's offset into vertex struct
     int index; // 0 (unused at the moment)
 };

 // Implementation of interleaved buffers.
 // 'T' is a struct which must include a null-terminated static array
 // 'VertexDescription* description'.
 // Example:
 /*
 struct Vertex
 {
     GLfloat position[3];
     GLfloat texCoord[2];
     GLfloat normal[3];
     GLbyte color[4];
     static VertexDescription description[];
 };

 VertexDescription Vertex::description[] = {
     {VertexDescription::Position, GL_FLOAT, SIZE_OF_MEMBER(Vertex, position) / sizeof(GLfloat), offsetof(Vertex, position), 0},
     {VertexDescription::TexCoord, GL_FLOAT, SIZE_OF_MEMBER(Vertex, texCoord) / sizeof(GLfloat), offsetof(Vertex, texCoord), 0},
     {VertexDescription::Normal, GL_FLOAT, SIZE_OF_MEMBER(Vertex, normal) / sizeof(GLfloat), offsetof(Vertex, normal), 0},
     {VertexDescription::Color, GL_BYTE, SIZE_OF_MEMBER(Vertex, color) / sizeof(GLbyte), offsetof(Vertex, color), 0},
     {VertexDescription::Null, 0, 0, 0, 0},
 };
 */
 template<class T>
 class GLVertexBuffer
 {
 public:
     GLVertexBuffer(int length, const T *data = 0, int mode = GL_STATIC_DRAW)
         : m_length(0)
         , m_mode(mode)
         , m_buffer(0)
         , m_failed(false)
     {
         GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::GLVertexBuffer", glGenBuffers && glBindBuffer && glBufferData, return)

                 glGenBuffers(1, &m_buffer);
                 glBindBuffer(GL_ARRAY_BUFFER, m_buffer);
                 glBufferData(GL_ARRAY_BUFFER, (m_length = length) * sizeof(T), data, mode);
     }

     ~GLVertexBuffer()
     {
         GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::~GLVertexBuffer", glDeleteBuffers, return)

         glDeleteBuffers(1, &m_buffer);
     }

     void bind()
     {
         GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::bind", glBindBuffer, return)

         glBindBuffer(GL_ARRAY_BUFFER, m_buffer);
         for (VertexDescription *desc = T::description; desc->field != VertexDescription::Null; ++desc) {
             switch (desc->field) {
             case VertexDescription::Position:
                 glVertexPointer(desc->count, desc->type, sizeof(T), BUFFER_OFFSET(desc->offset));
                 glEnableClientState(GL_VERTEX_ARRAY);
                 break;
             case VertexDescription::TexCoord:
                 glTexCoordPointer(desc->count, desc->type, sizeof(T), BUFFER_OFFSET(desc->offset));
                 glEnableClientState(GL_TEXTURE_COORD_ARRAY);
                 break;
             case VertexDescription::Normal:
                 glNormalPointer(desc->type, sizeof(T), BUFFER_OFFSET(desc->offset));
                 glEnableClientState(GL_NORMAL_ARRAY);
                 break;
             case VertexDescription::Color:
                 glColorPointer(desc->count, desc->type, sizeof(T), BUFFER_OFFSET(desc->offset));
                 glEnableClientState(GL_COLOR_ARRAY);
                 break;
             default:
                 break;
             }
         }
     }

     void unbind()
     {
         GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::unbind", glBindBuffer, return)

         glBindBuffer(GL_ARRAY_BUFFER, 0);
         for (VertexDescription *desc = T::description; desc->field != VertexDescription::Null; ++desc) {
             switch (desc->field) {
             case VertexDescription::Position:
                 glDisableClientState(GL_VERTEX_ARRAY);
                 break;
             case VertexDescription::TexCoord:
                 glDisableClientState(GL_TEXTURE_COORD_ARRAY);
                 break;
             case VertexDescription::Normal:
                 glDisableClientState(GL_NORMAL_ARRAY);
                 break;
             case VertexDescription::Color:
                 glDisableClientState(GL_COLOR_ARRAY);
                 break;
             default:
                 break;
             }
         }
     }

     int length() const {return m_length;}

     T *lock()
     {
         GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::lock", glBindBuffer && glMapBuffer, return 0)

         glBindBuffer(GL_ARRAY_BUFFER, m_buffer);
         //glBufferData(GL_ARRAY_BUFFER, m_length, NULL, m_mode);
         GLvoid* buffer = glMapBuffer(GL_ARRAY_BUFFER, GL_READ_WRITE);
         m_failed = (buffer == 0);
         return reinterpret_cast<T *>(buffer);
     }

     void unlock()
     {
         GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::unlock", glBindBuffer && glUnmapBuffer, return)

         glBindBuffer(GL_ARRAY_BUFFER, m_buffer);
         glUnmapBuffer(GL_ARRAY_BUFFER);
     }

     bool failed()
     {
         return m_failed;
     }

 private:
     int m_length, m_mode;
     GLuint m_buffer;
     bool m_failed;
 };

 template<class T>
 class GLIndexBuffer
 {
 public:
     GLIndexBuffer(int length, const T *data = 0, int mode = GL_STATIC_DRAW)
         : m_length(0)
         , m_mode(mode)
         , m_buffer(0)
         , m_failed(false)
     {
         GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::GLIndexBuffer", glGenBuffers && glBindBuffer && glBufferData, return)

         glGenBuffers(1, &m_buffer);
         glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_buffer);
         glBufferData(GL_ELEMENT_ARRAY_BUFFER, (m_length = length) * sizeof(T), data, mode);
     }

     ~GLIndexBuffer()
     {
         GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::~GLIndexBuffer", glDeleteBuffers, return)

         glDeleteBuffers(1, &m_buffer);
     }

     void bind()
     {
         GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::bind", glBindBuffer, return)

         glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_buffer);
     }

     void unbind()
     {
         GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::unbind", glBindBuffer, return)

         glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
     }

     int length() const {return m_length;}

     T *lock()
     {
         GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::lock", glBindBuffer && glMapBuffer, return 0)

         glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_buffer);
         GLvoid* buffer = glMapBuffer(GL_ELEMENT_ARRAY_BUFFER, GL_READ_WRITE);
         m_failed = (buffer == 0);
         return reinterpret_cast<T *>(buffer);
     }

     void unlock()
     {
         GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::unlock", glBindBuffer && glUnmapBuffer, return)

         glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_buffer);
         glUnmapBuffer(GL_ELEMENT_ARRAY_BUFFER);
     }

     bool failed()
     {
         return m_failed;
     }

 private:
     int m_length, m_mode;
     GLuint m_buffer;
     bool m_failed;
 };

 #endif