OpenGL学习05_点画模式(点画多边形)

在默认情况下，填充多边形是用实心模式绘制的。此外，它们还可以使用一种32位×32位的窗口对齐的点画模式。glPolygonStipple()函数用于指定多边形的点画模式。

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voidglPolygonStipple(constGLubyte*mask);

定义填充多边形的当前点画模式。mask参数是一个指向32×32位图的指针，后者被解释为0和1的掩码。如果模式中出现的是1，那么多边形中对应的像素就被绘制；如果出现的是0，多边形中对应的像素就不被绘制。

下面通过一个绘制小强的Demo演示一下多边形的点画。

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//

//main.cpp

//OpenGL_04_Polygon

//

//Createdbyappleon14/12/30.

//Copyright(c)2014年cc.Allrightsreserved.

//

#include<iostream>

#include<GLUT/GLUT.h>

/**

*初始化操作

*/

voidinit(){

glClearColor(0.0f,0.0f,0.0f,0.0f);

//设置着色模式，GL_FLAT采用恒定着色，使用图元中某个顶点的颜色来渲染整个图元。

glShadeModel(GL_FLAT);

}

/**

*展示绘制效果

*/

voiddisplay(){

GLubytefly[]={

0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,

0x03,0x80,0x01,0xC0,0x06,0xC0,0x03,0x60,

0x04,0x60,0x06,0x20,0x04,0x30,0x0C,0x20,

0x04,0x18,0x18,0x20,0x04,0x0C,0x30,0x20,

0x04,0x06,0x60,0x20,0x44,0x03,0xC0,0x22,

0x44,0x01,0x80,0x22,0x44,0x01,0x80,0x22,

0x44,0x01,0x80,0x22,0x44,0x01,0x80,0x22,

0x44,0x01,0x80,0x22,0x44,0x01,0x80,0x22,

0x66,0x01,0x80,0x66,0x33,0x01,0x80,0xCC,

0x19,0x81,0x81,0x98,0x0C,0xC1,0x83,0x30,

0x07,0xe1,0x87,0xe0,0x03,0x3f,0xfc,0xc0,

0x03,0x31,0x8c,0xc0,0x03,0x33,0xcc,0xc0,

0x06,0x64,0x26,0x60,0x0c,0xcc,0x33,0x30,

0x18,0xcc,0x33,0x18,0x10,0xc4,0x23,0x08,

0x10,0x63,0xC6,0x08,0x10,0x30,0x0c,0x08,

0x10,0x18,0x18,0x08,0x10,0x00,0x00,0x08

};

GLubytehalftone[]={

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55,

0xAA,0xAA,0xAA,0xAA,0x55,0x55,0x55,0x55

};

//清理颜色缓冲区

glClear(GL_COLOR_BUFFER_BIT);

//设置绘制颜色(白)

glColor3f(1.0,1.0,1.0);

//1.绘制一个矩形(正方形)，左侧

glRectf(25.0,25.0,125.0,125.0);

//开启多边形点画模式

glEnable(GL_POLYGON_STIPPLE);

//2.通过点画模式绘制一个小强的矩形

//小强矩形区域32*32位

glPolygonStipple(fly);

//指定小强所在的矩形区域

glRectf(125.0,25.0,225.0,125.0);

//3.通过点画绘制一张网图

glPolygonStipple(halftone);

//指定网图所在的矩形区域

glRectf(225.0,25.0,325.0,125.0);

//关闭多边形点画模式

glDisable(GL_POLYGON_STIPPLE);

glFlush();

}

/**

*调整窗口尺寸

*

*@paramwidth宽度

*@paramheight高度

*/

voidreshape(intwidth,intheight){

//设置视口矩形区域，在默认情况下，视口被设置为占据打开窗口的整个像素矩形

glViewport(0,0,(GLsizei)width,(GLsizei)height);

//对投影矩阵应用随后的矩阵操作

glMatrixMode(GL_PROJECTION);

//等于是将之前矩阵变换导致变化过的栈顶矩阵重新归位，置为单位矩阵！等于是之前的矩阵变换带来的影响到此为止了！

glLoadIdentity();

//指定2D裁剪坐标系，naer和far使用默认值-1和1

gluOrtho2D(0.0,(GLdouble)width,0.0,(GLdouble)height);

}

/**

*键盘事件回调

*

*@paramkey键位

*@paramx宽度

*@paramy高度

*/

voidkeyboard(unsignedcharkey,intx,inty){

switch(key){

//ESC

case27:

exit(0);

break;

}

}

intmain(intargc,constchar*argv[]){

//初始化GLUT库

glutInit(&argc,(char**)argv);

//设置双缓冲，RGB像素格式的窗口

glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);

//设置窗口大小

glutInitWindowSize(350,150);

//设置窗口坐标

glutInitWindowPosition(100,100);

//创建窗口

glutCreateWindow("Lines");

//初始化操作

init();

//设置展示的回调方法

glutDisplayFunc(display);

glutReshapeFunc(reshape);

glutKeyboardFunc(keyboard);

//绘制线程开始循环

glutMainLoop();

return0;

}

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