qt opengl lesson3 给三角形和正方形上色

之前每章的结构基本相同，很多函数不需要现在明白什么道理，可能设计到一些空间图形和计算机学的知识，可以放在需要的时候专门学习。

#-------------------------------------------------
#
# Project created by QtCreator 2017-01-19T22:12:43
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets opengl

TARGET = lesson3
TEMPLATE = app

# The following define makes your compiler emit warnings if you use
# any feature of Qt which as been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0


SOURCES += main.cpp\
        myglwidget.cpp

HEADERS  += myglwidget.h

LIBS += -lglut -lGLU

#ifndef MYGLWIDGET_H
#define MYGLWIDGET_H

#include <QGLWidget>
#include <QKeyEvent>

class MyGLwidget : public QGLWidget {

    Q_OBJECT

public:
    MyGLwidget(QWidget *parent = 0);
    ~MyGLwidget();

protected:
    virtual void paintGL();
    virtual void initializeGL();
    virtual void resizeGL(int width, int height);
    virtual void keyPressEvent(QKeyEvent *event);

private:
    bool mFullScreen;
};

#endif // MYGLWIDGET_H

#include "myglwidget.h"
#include <GL/glu.h>
#include <QApplication>

MyGLwidget::MyGLwidget(QWidget *parent)
{
    showNormal();
}

MyGLwidget::~MyGLwidget()
{

}

void MyGLwidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(-1.5f, 0.0f, -6.0f);

    // draw triangle
    glBegin(GL_TRIANGLES);
        glColor3f(1.0f, 0.0f, 0.0f);
        glVertex3f(0.0f, 1.0f, 0.0f);

        glColor3f(0.0f, 1.0f, 0.0f);
        glVertex3f(-1.2f, -1.0f, 0.0f);

        glColor3f(0.0f, 0.0f, 1.0f);
        glVertex3f(1.2f, -1.0f, 0.0f);
     glEnd();

     glTranslatef(3.0f, 0.0f, 0.0f);
     glColor3f(1.0f, 1.0f, 0.0f);
     glBegin(GL_QUADS);
        glVertex3f(-1.0f, 1.0f, 0.0f);
        glVertex3f(1.0f, 1.0f, 0.0f);
        glVertex3f(1.0f, -1.0f, 0.0f);
        glVertex3f(-1.0f, -1.0f, 0.0f);
     glEnd();
}

void MyGLwidget::initializeGL()
{
    glShadeModel(GL_SMOOTH);
    glClearColor(0.0f, 0.0f, 1.0f, 0.0f);
    glClearDepth(1.0f);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);

    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
}

void MyGLwidget::resizeGL(int width, int height)
{
    if (height == 0)
        height = 1;
    glViewport(0, 0, width, height);

    glMatrixMode(GL_PROJECTION);

    glLoadIdentity();
    gluPerspective(45.0f, (GLfloat)width/(GLfloat)height, 0.1f, 100.0f);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

void MyGLwidget::keyPressEvent(QKeyEvent *event)
{
    switch(event->key()) {
    case Qt::Key_F2:
        mFullScreen = !mFullScreen;
        if (mFullScreen)
            showFullScreen();
        else
            showNormal();
        updateGL();
        break;
    case Qt::Key_Escape:
        qApp->exit();
        break;
    }
}

#include "myglwidget.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MyGLwidget w;
    w.show();

    return a.exec();
}