前面繪製的圖片還是純白色的,並且看上去還是2D的正方形,這一節將爲圖形每個頂點着色,然後添加其他的面來形成3D效果。
//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"
"in vec4 vColor; \n"
"out vec4 color; \n"
"void main() { \n"
" color = vColor; \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 =
"in vec4 color; \n"
"out vec4 fColor; \n"
"void main() { \n"
" fColor = color; \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, 20*sizeof(GLfloat));
GLuint vPosition = program->attributeLocation("vPosition");
program->setAttributeBuffer(vPosition, GL_FLOAT, 0, 2, 0);
glEnableVertexAttribArray(vPosition);
// 頂點顏色
GLfloat colors[] = {
1.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 1.0f,
1.0f, 1.0f, 1.0f
};
vbo.write(8*sizeof(GLfloat), colors, 12*sizeof(GLfloat));
GLuint vColor = program->attributeLocation("vColor");
program->setAttributeBuffer(vColor, GL_FLOAT, 8*sizeof(GLfloat), 3, 0);
glEnableVertexAttribArray(vColor);
// 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: