基于Qt的OpenGL2.1固定管线渲染基础框架

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本文介绍了一个使用OpenGL进行2D图形绘制的Qt应用实例。该实例包括了初始化OpenGL环境、设置视口大小、绘制彩色四边形等功能，并实现了鼠标点击更新画面的效果。

#ifndef CVXRENDERWIDGET_H
#define CVXRENDERWIDGET_H

#include <gl/glew.h>

#include <QGLWidget>

class QMouseEvent;
class CVxRenderWidget : public QGLWidget
{
   Q_OBJECT

public:
   CVxRenderWidget( const QGLFormat & format,QWidget * parent = 0);
   ~CVxRenderWidget();


protected:
   virtual       void initializeGL();
   virtual       void resizeGL(int w, int h);
   virtual       void paintGL();

   virtual       void mousePressEvent(QMouseEvent* pEvent);

private:

   GLuint m_iBuf[3];
};

#endif // CVXRENDERWIDGET_H

#include "CVxRenderWidget.h"
#include <QMouseEvent>

CVxRenderWidget::CVxRenderWidget( const QGLFormat & format,QWidget * parent)
   : QGLWidget(format,parent )
{
}

CVxRenderWidget::~CVxRenderWidget()
{
}

void CVxRenderWidget::mousePressEvent( QMouseEvent* pEvent)
{
   update();
}
void CVxRenderWidget::initializeGL()
{
   GLenum iInit = glewInit();
   if (iInit == GLEW_OK)
   {
       const char* pVendor = (const char*)glGetString(GL_VENDOR);
       const char* pCardName = (const char*)glGetString(GL_RENDERER);
       const char* version = (const char*)glGetString(GL_VERSION);
       int main_version, sub_version, release_version;
       sscanf(version, "%d.%d.%d", &main_version, &sub_version, &release_version);

   }

   glClearColor(0.0, 0.0, 0.0, 0.0);

   glEnable(GL_POINT_SIZE);
   glPointSize(10);

   glEnable(GL_DEPTH_TEST);
   glEnable(GL_BLEND);
   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
   glEnable(GL_POINT_SMOOTH);
   glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);
   glEnable(GL_LINE_SMOOTH);
   glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);

   glShadeModel(GL_SMOOTH);

   glGenBuffers(3, m_iBuf);
}

void CVxRenderWidget::resizeGL(int w, int h)
{

   glViewport(0,0,w,h);

   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(-0.5 * w, 0.5 * w, -0.5 * h, 0.5 * h, -100.0, 100);


   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();

   gluLookAt(0, 0,0, 0,0,-1, 0,1,0);

   int iW = w;
   int iH = h;
   GLfloat vertexArray[][3] =
   {
       {-0.5 * iW, 0.5 * iH, 0},
       {0.5 * iW, 0.5 * iH, 0},
       {0.5 * iW, -0.5 * iH, 0},
       {-0.5 * iW, -0.5 * iH, 0}
   };
   glBindBuffer(GL_ARRAY_BUFFER, m_iBuf[0]);
   glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 3 * 4, (void*)vertexArray, GL_STATIC_DRAW);

   GLfloat colorArray[][3] =
   {
       {1.0, 0.0, 0.0},
       {0.0, 1.0, 0.0},
       {0.0, 0.0, 1.0},
       {0.5, 0.5, 0.5}
   };
   glBindBuffer(GL_ARRAY_BUFFER, m_iBuf[1]);
   glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 3 * 4, (void*)colorArray, GL_STATIC_DRAW);

   GLubyte indexes[] = {0, 1, 2, 3};
   glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,m_iBuf[2]);
   glBufferData(GL_ELEMENT_ARRAY_BUFFER,sizeof(GLubyte)* 4, (void*)indexes,GL_STATIC_DRAW);


}

void CVxRenderWidget::paintGL()
{
   glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

   int iW = width();
   int iH = height();

   glEnableClientState(GL_VERTEX_ARRAY);
   glEnableClientState(GL_COLOR_ARRAY);

   glBindBuffer(GL_ARRAY_BUFFER,m_iBuf[0]);
   glVertexPointer(3,GL_FLOAT,0,0);

   glBindBuffer(GL_ARRAY_BUFFER, m_iBuf[1]);
   glColorPointer (3, GL_FLOAT, 0,0);

   glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_iBuf[2]);
   glDrawElements(GL_QUADS, 4, GL_UNSIGNED_BYTE, 0);

}

#ifndef QTOPENGL_H
#define QTOPENGL_H

#include <QtGui/QMainWindow>
class CVxRenderWidget;

class QtOpenGL : public QMainWindow
{
   Q_OBJECT

public:
   QtOpenGL(QWidget *parent = 0, Qt::WFlags flags = 0);
   ~QtOpenGL();
protected:
   virtual void resizeEvent(QResizeEvent* pEvent);

private:

   CVxRenderWidget* m_pRenderWidget;
};

#endif // QTOPENGL_H

#include "qtopengl.h"

#include "CVxRenderWidget.h"

QtOpenGL::QtOpenGL(QWidget *parent, Qt::WFlags flags)
   : QMainWindow(parent, flags)
{
   QGLFormat fmt(QGLFormat(QGL::DoubleBuffer | QGL::DepthBuffer | QGL::Rgba | QGL::StencilBuffer | QGL::AccumBuffer));
   m_pRenderWidget = new CVxRenderWidget(fmt,this);
}

QtOpenGL::~QtOpenGL()
{

}
void QtOpenGL::resizeEvent(QResizeEvent* pEvent)
{
   m_pRenderWidget->setGeometry(0,0,width(), height());
}

#include "qtopengl.h"
#include <QtGui/QApplication>

int main(int argc, char *argv[])
{

   QApplication a(argc, argv);
   QtOpenGL w;
   w.show();
   return a.exec();
}