上一教程我們應用glVertexAttribPointer繪製多邊形,這一節,我們通過使用緩存
基礎知識:
和上一節的區別,
//myopenglwidget.h
#ifndef MYOPENGLWIDGET_H
#define MYOPENGLWIDGET_H
#include <QOpenGLWidget>
#include <QOpenGLFunctions>
#include <QOpenGLBuffer>
class QOpenGLShaderProgram;
class MyOpenGLWidget : public QOpenGLWidget, protected QOpenGLFunctions
{
Q_OBJECT
public:
explicit MyOpenGLWidget(QWidget *parent = 0);
protected:
void initializeGL();
void paintGL();
void resizeGL(int width, int height);
private:
QOpenGLShaderProgram *program;
QOpenGLBuffer vbo;
};
#endif // MYOPENGLWIDGET_H
//myopenglwidget.cpp
#include "myopenglwidget.h"
#include <QOpenGLShaderProgram>
MyOpenGLWidget::MyOpenGLWidget(QWidget *parent)
: QOpenGLWidget(parent)
{
}
void MyOpenGLWidget::initializeGL()
{
// 爲當前環境初始化OpenGL函數
initializeOpenGLFunctions();
// 創建頂點着色器
QOpenGLShader *vshader = new QOpenGLShader(QOpenGLShader::Vertex, this);
const char *vsrc =
"in vec4 vPosition; \n"
"void main() { \n"
" gl_Position = vPosition; \n"
"} \n";
vshader->compileSourceCode(vsrc);
// 創建片段着色器
QOpenGLShader *fshader = new QOpenGLShader(QOpenGLShader::Fragment, this);
const char *fsrc =
"void main() { \n"
" gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);\n"
"} \n";
fshader->compileSourceCode(fsrc);
// 創建着色器程序
program = new QOpenGLShaderProgram;
program->addShader(vshader);
program->addShader(fshader);
program->link();
program->bind();
}
void MyOpenGLWidget::resizeGL(int , int )
{
}
void MyOpenGLWidget::paintGL()
{
int w = width();
int h = height();
int side = qMin(w, h);
glViewport((w - side) / 2, (h - side) / 2, side, side);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// 頂點位置
GLfloat vertices[] = {
-0.8f, 0.8f,
-0.8f, -0.8f,
0.8f, -0.8f,
0.8f, 0.8f
};
vbo.create();
vbo.bind();
vbo.allocate(vertices, 8*sizeof(GLfloat));
GLuint vPosition = program->attributeLocation("vPosition");
//爲着色器中的位置設定頂點緩存
program->setAttributeBuffer(vPosition, GL_FLOAT, 0, 2, 0);
//啓用定點數組
glEnableVertexAttribArray(vPosition);
// 繪製
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
}
//main.cpp
#include <QApplication>
#include "myopenglwidget.h"
int main(int argc, char *argv[])
{
QApplication app(argc,argv);
MyOpenGLWidget w;
w.resize(400, 300);
w.show();
return app.exec();
}
運行結果: