发信人: yxy (田丝丝#冬眠的小肥鹰), 信区: GAME_Designer
标 题: OPENGL(12)
发信站: BBS 水木清华站 (Sun Feb 15 15:41:17 1998)
此次讲解OPENGL复杂建模方式，将分几个部分完成，这篇先介绍图原扩展：
如何利用专用函数精确绘制平面图形。下次会讲解如何利用法向量生成曲面。
1.点和线
void glPointSize(GLfloat size);
设置点的宽度，size必须>0，缺省1
void glLineWidth(GLfoat width);
设置线宽，width>0，缺省为1
void glLineStipple(GLint factor,GLushort pattern);
设置线的模式，factor用于对模式进行拉伸的比例因子，pattern是线的模式
例如11001100是虚线（1绘制，0不绘制）
必须要启用glEnable(GL_LINE_STIPPLE)才能使用以上函数，不再使用时调用
glDisable(GL_LINE_STIPPLE)关闭，这与以前的glEnable();glDisable();的
用法都是类似的。请看下面例子：
///////////////////////////////////////////////////////////////////
//sample.cpp
#include "glos.h"
#include <GL/gl.h>
#include <GL/glaux.h>
#include "windows.h"
void myinit(void);
void CALLBACK display(void);
void CALLBACK reshape(GLsizei w,GLsizei h);
void myinit(void)
{
auxInitDisplayMode(AUX_SINGLE|AUX_RGBA);
auxInitPosition(0,0,600,500);
auxInitWindow("sample1");
glClearColor(0.0,0.0,0.0,0.0);
glClear(GL_COLOR_BUFFER_BIT);
glShadeModel(GL_FLAT);
}
/*
void CALLBACK reshape(GLsizei w,GLsizei h)
{
glViewport(0,0,w,h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if(w<=h)
glOrtho(-4.0,4.0,-4.0*(GLfloat)h/(GLfloat)w,
4.0*(GLfloat)h/(GLfloat)w,-4.0,4.0);
else
glOrtho(-4.0*(GLfloat)h/(GLfloat)w,
4.0*(GLfloat)h/(GLfloat)w,-4.0,4.0,-4.0,4.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
*/
//自定义的绘制直线的函数，参数为起始点和终止点坐标
void line2i(GLint x1,GLint y1,GLint x2,GLint y2)
{
glBegin(GL_LINES);
glVertex2f(x1,y1);
glVertex2f(x2,y2);
glEnd();
}
void CALLBACK display(void)
{
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
//首先绘制一系列点，点的大小不断增加
int i;
glColor3f(0.8,0.6,0.4);
for(i=1;i<=10;i++)
{
glPointSize(i*2);
glBegin(GL_POINTS);
glVertex2f(30.0+((GLfloat)i*50.0),330.0);
glEnd();
}
//再绘制两条虚线，第二条比第一条松散一些，由pattern参数即可看出
glEnable(GL_LINE_STIPPLE);
glLineStipple(1,0x0101);//间隔1位
glColor3f(1.0,0.0,0.0);
line2i(20,250,250,250);
glLineStipple(1,0x00ff);//间隔2位
glColor3f(0.0,0.0,1.0);
line2i(300,250,550,250);
//改变线的绘制宽度的效果--加宽
//重新画出上面两条虚线
glLineWidth(5.0);
glEnable(GL_LINE_STIPPLE);
glLineStipple(1,0x0101);
glColor3f(1.0,0.0,0.0);
line2i(50,150,250,150);
glLineStipple(1,0x00ff);
glColor3f(0.0,0.0,1.0);
line2i(300,150,550,150);
glFlush();
}
void main(void)
{
myinit();
// auxReshapeFunc(reshape);
auxMainLoop(display);
}
//end of sample
//////////////////////////////////////////////
2.多边形
void glPolygonMode(GLenum face,GLenum mode);
控制多边形指定面的绘图模式，
face为：GL_FRONT GL_BACK或GL_FRONT_AND BACK
mode为：GL_POINT GL_LINE或GL_FILL表示多边型的轮廓点、轮廓线和填充模式
的绘制方式。缺省是填充方式。
void glPolygonStipple(const GLubyte *mask);
其中mask必须是指向32*32的位图指针，1是绘制、0不绘制
使用上述函数也要调用：
glEnable(GL_POLYGON-STIPPLE);
glDisable(GL_POLYGON_STIPPLE);
请看下面例子：
/////////////////////////////////////////////
//sample.cpp
#include "glos.h"
#include <GL/gl.h>
#include <GL/glaux.h>
#include "windows.h"
void myinit(void);
void CALLBACK display(void);
void CALLBACK reshape(GLsizei w,GLsizei h);
//定义填充模式32*32点阵
GLubyte pattern[]={
0x00,0x01,0x80,0x00,
0x00,0x03,0xc0,0x00,
0x00,0x07,0xe0,0x00,
0x00,0x0f,0xf0,0x00,
0x00,0x1f,0xf8,0x00,
0x00,0x3f,0xfc,0x00,
0x00,0x7f,0xfe,0x00,
0x00,0xff,0xff,0x00,
0x01,0xff,0xff,0x80,
0x03,0xff,0xff,0xc0,
0x07,0xff,0xff,0xe0,
0x0f,0xff,0xff,0xf0,
0x1f,0xff,0xff,0xf8,
0x3f,0xff,0xff,0xfc,
0x7f,0xff,0xff,0xfe,
0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,
0x7f,0xff,0xff,0xfe,
0x3f,0xff,0xff,0xfc,
0x1f,0xff,0xff,0xf8,
0x0f,0xff,0xff,0xf0,
0x07,0xff,0xff,0xe0,
0x03,0xff,0xff,0xc0,
0x01,0xff,0xff,0x80,
0x00,0xff,0xff,0x00,
0x00,0x7f,0xfe,0x00,
0x00,0x3f,0xfc,0x00,
0x00,0x1f,0xf8,0x00,
0x00,0x0f,0xf0,0x00,
0x00,0x07,0xe0,0x00,
0x00,0x03,0xc0,0x00,
0x00,0x01,0x80,0x00
};
void myinit(void)
{
auxInitDisplayMode(AUX_SINGLE|AUX_RGBA);
auxInitPosition(0,0,400,400);
auxInitWindow("sample1");
glClearColor(0.0,0.0,0.0,0.0);
glClear(GL_COLOR_BUFFER_BIT);
glShadeModel(GL_FLAT);
}
/*
void CALLBACK reshape(GLsizei w,GLsizei h)
{
glViewport(0,0,w,h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if(w<=h)
glOrtho(-4.0,4.0,-4.0*(GLfloat)h/(GLfloat)w,
4.0*(GLfloat)h/(GLfloat)w,-4.0,4.0);
else
glOrtho(-4.0*(GLfloat)h/(GLfloat)w,
4.0*(GLfloat)h/(GLfloat)w,-4.0,4.0,-4.0,4.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
*/
void CALLBACK display(void)
{
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
//选用兰色作为填充色
glColor3f(0.0,0.0,1.0);
//启用多边形绘制模式
glEnable(GL_POLYGON_STIPPLE);
//利用定义好的填充模式绘制多边形
glPolygonStipple(pattern);
//绘制长方形
glRectf(48.0,80.0,210.0,305.0);
glFlush();
}
void main(void)
{
myinit();
// auxReshapeFunc(reshape);
auxMainLoop(display);
}
//end of sample
例子中的运行结果是给出一个表面有定义图样的长方形
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