這一課會(huì)把第二課中的三角形繞Y軸逆時(shí)針旋轉(zhuǎn)45°，正方形繞X軸順時(shí)針旋轉(zhuǎn)45°

頭文件中添加兩個(gè)變量表示三角形和正方形旋轉(zhuǎn)的角度。

private:
????QOpenGLContext?*m_context;
????GLfloat		rtri;			//?用于三角形的角度
????GLfloat		rquad;			//?用于正方形的角度

在構(gòu)造函數(shù)中賦值

Lesson3::Lesson3(QWindow?*parent)?:
????QWindow(parent)
??,?m_context(0)
{
????setSurfaceType(QWindow::OpenGLSurface);
????rtri=45.0f;	??//?三角形的旋轉(zhuǎn)角度
????rquad=-45.0f;?//?正方形的旋轉(zhuǎn)角度
}

接下來需要修改render函數(shù)

void?Lesson3::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(duì)gl庫函數(shù)的封裝，方便使用。因此我們可以自己
????//?寫一個(gè)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);?//?左移1.5單位，并移入屏幕6.0
????glRotatef(rtri,0.0f,1.0f,0.0f);	//?繞Y軸旋轉(zhuǎn)三角形
????glBegin(GL_TRIANGLES);			//?繪制三角形
????glColor3f(1.0f,0.0f,0.0f);		//?設(shè)置當(dāng)前色為紅色
????glVertex3f(?0.0f,?1.0f,?0.0f);	//?上頂點(diǎn)
????glColor3f(0.0f,1.0f,0.0f);		//?設(shè)置當(dāng)前色為綠色
????glVertex3f(-1.0f,-1.0f,?0.0f);	//?左下
????glColor3f(0.0f,0.0f,1.0f);		//?設(shè)置當(dāng)前色為藍(lán)色
????glVertex3f(?1.0f,-1.0f,?0.0f);	//?右下
????glEnd();????????????????????????//?三角形繪制結(jié)束
????//?注意：這里用原來的glTranslatef(3.0f,0.0f,0.0f);?換成了下面這兩句
????glLoadIdentity();
????glTranslatef(1.5f,0.0f,-6.0f);??//?右移1.5單位，并移入屏幕6.0
????glRotatef(rquad,1.0f,0.0f,0.0f);//?繞X軸旋轉(zhuǎn)四邊形
????glColor3f(0.5f,0.5f,1.0f);	????//?一次性將當(dāng)前色設(shè)置為紫色
????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
}

運(yùn)行效果

glRotatef函數(shù)的用法：
函數(shù)原型:
? ? ? void glRotated(GLdouble angle,GLdouble x,GLdouble y,GLdouble z)
? ? ? void glRotatef(GLfloat angle,GLfloat x,GLfloat y,GLdouble z)
函數(shù)說明：
? ? ?這兩個(gè)函數(shù)用來計(jì)算旋轉(zhuǎn)矩陣，該矩陣圍繞原點(diǎn)到點(diǎn)(x,y,z)的向量逆時(shí)針旋轉(zhuǎn)angle度。
關(guān)于逆時(shí)針與順時(shí)針，可用右手定則：

即手握住某個(gè)坐標(biāo)軸，大拇指指向某軸的正方向，其余四個(gè)手指的彎曲方向即為繞某軸旋轉(zhuǎn)的逆時(shí)針方向；反之為順時(shí)針方向。