Qt5版NeHe OpenGL教程之一：你的第一個多邊形

我們添加了一個三角形和一個四邊形。也許你認(rèn)為這很簡單，但你已經(jīng)邁出了一大步，要知道任何在OpenGL中繪制的模型都會被分解為這兩種簡單的圖形。

lesson1.h

#ifndef?LESSON1_H
#define?LESSON1_H


#include#includeclass?QPainter;
class?QOpenGLContext;
class?QOpenGLPaintDevice;

class?Lesson1?:?public?QWindow,?QOpenGLFunctions_1_0
{
????Q_OBJECT
public:
????explicit?Lesson1(QWindow?*parent?=?0);
????~Lesson1();

????virtual?void?render(QPainter?*);
????virtual?void?render();
????virtual?void?initialize();

public?slots:
????void?renderNow();

protected:
????void?exposeEvent(QExposeEvent?*);
????void?resizeEvent(QResizeEvent?*);

private:
????void?myPerspective(?GLdouble?fov,?GLdouble?aspectRatio,?GLdouble?zNear,?GLdouble?zFar?);

private:
????QOpenGLContext?*m_context;

};

#endif?//?LESSON1_H

lesson1.cpp

#include?"lesson1.h"

#include#include#include#includeLesson1::Lesson1(QWindow?*parent)?:
????QWindow(parent)
??,?m_context(0)
{
????setSurfaceType(QWindow::OpenGLSurface);
}

Lesson1::~Lesson1()
{

}

void?Lesson1::render(QPainter?*painter)
{
????Q_UNUSED(painter);
}

void?Lesson1::myPerspective(?GLdouble?fov,?GLdouble?aspectRatio,?GLdouble?zNear,?GLdouble?zFar?)
{
????//?使用glu庫函數(shù)，需要添加glu.h頭文件
????//?gluPerspective(fov,?aspectRatio,?zNear,?zFar);
????GLdouble?rFov?=?fov?*?3.14159265?/?180.0;
????glFrustum(?-zNear?*?tan(?rFov?/?2.0?)?*?aspectRatio,
???????????????zNear?*?tan(?rFov?/?2.0?)?*?aspectRatio,
???????????????-zNear?*?tan(?rFov?/?2.0?),
???????????????zNear?*?tan(?rFov?/?2.0?),
???????????????zNear,?zFar?);
}

void?Lesson1::render()
{
????glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

????glViewport(0,0,(GLint)width(),(GLint)height());?//?重置當(dāng)前視口
????glMatrixMode(GL_PROJECTION);????????????????????//?選擇投影矩陣
????glLoadIdentity();???????????????????????????????//?重置投影矩陣為單位矩陣
????//?glu庫函數(shù)Qt不支持，但是glu庫函數(shù)是對gl庫函數(shù)的封裝，方便使用。因此我們可以自己
????//?寫一個類似gluPerspective的函數(shù)myPerspective，用于設(shè)置透視。
????//gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
????myPerspective(45.0,(GLfloat)width()/(GLfloat)height(),0.1,100.0);

????glMatrixMode(GL_MODELVIEW);//?選擇模型視圖矩陣
????glLoadIdentity();??????????//?重置模型視圖矩陣為單位矩陣

????glTranslatef(-1.5f,0.0f,-6.0f);
????glBegin(GL_TRIANGLES);			//?繪制三角形
????glVertex3f(?0.0f,?1.0f,?0.0f);	//?上頂點
????glVertex3f(-1.0f,-1.0f,?0.0f);	//?左下
????glVertex3f(?1.0f,-1.0f,?0.0f);	//?右下
????glEnd();????????????????????????//?三角形繪制結(jié)束
????glTranslatef(3.0f,0.0f,0.0f);
????glBegin(GL_QUADS);				//?繪制正方形
????glVertex3f(-1.0f,?1.0f,?0.0f);	//?左上
????glVertex3f(?1.0f,?1.0f,?0.0f);	//?右上
????glVertex3f(?1.0f,-1.0f,?0.0f);	//?左下
????glVertex3f(-1.0f,-1.0f,?0.0f);	//?右下
????glEnd();					????//?正方形繪制結(jié)束
}

void?Lesson1::initialize()
{
????glShadeModel(GL_SMOOTH);??????????????//?啟用平滑著色
????glClearColor(0.0f,?0.0f,?0.0f,?0.0f);?//?黑色背景
????glClearDepth(1.0f);???????????????????//?設(shè)置深度緩存
????glEnable(GL_DEPTH_TEST);??????????????//?啟用深度測試
????glDepthFunc(GL_LEQUAL);???????????????//?深度測試類型
????//?接著告訴OpenGL我們希望進行最好的透視修正。這會十分輕微的影響性能。但使得透視圖看起來好一點。
????glHint(GL_PERSPECTIVE_CORRECTION_HINT,?GL_NICEST);
}

void?Lesson1::renderNow()
{
????if?(!isExposed())
????????return;

????bool?needsInitialize?=?false;

????if?(!m_context)?{
????????m_context?=?new?QOpenGLContext(this);
????????m_context->setFormat(requestedFormat());
????????m_context->create();

????????needsInitialize?=?true;
????}

????m_context->makeCurrent(this);

????if?(needsInitialize)?{
????????initializeOpenGLFunctions();
????????initialize();
????}

????render();

????m_context->swapBuffers(this);
}

void?Lesson1::exposeEvent(QExposeEvent?*event)
{
????Q_UNUSED(event);

????if?(isExposed())
????????renderNow();
}

void?Lesson1::resizeEvent(QResizeEvent?*event)
{
????Q_UNUSED(event);

????if?(isExposed())
????????renderNow();
}

main.cpp

#include#includeint?main(int?argc,?char?*argv[])
{
????QGuiApplication?app(argc,?argv);

????QSurfaceFormat?format;
????format.setSamples(16);

????Lesson1?window;
????window.setFormat(format);
????window.resize(640,?480);
????window.show();

????return?app.exec();
}

運行效果

源碼中用到的OpenGL庫函數(shù)可以參考：

OpenGL之glViewPort函數(shù)的用法

OpenGL之glLoadIdentity函數(shù)的用法

OpenGL之glMatrixMode函數(shù)的用法

實際上僅用如下代碼就能畫出一個三角形

void?Lesson1::render()
{
????glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

????glViewport(0,0,(GLint)width(),(GLint)height());?//?重置當(dāng)前視口
????glBegin(GL_TRIANGLES);			//?繪制三角形
????glVertex3f(?0.0f,?1.0f,?0.0f);	//?上頂點
????glVertex3f(-1.0f,-1.0f,?0.0f);	//?左下
????glVertex3f(?1.0f,-1.0f,?0.0f);	//?右下
????glEnd();????????????????????????//?三角形繪制結(jié)束
}