OpenGL绘制圆角矩形、空心圆角矩形
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大致思路，通过cos , sin 求出指定半径在各个角度上的点，由LINE_STRIP 或者LINE_LOOP
连接成一个圆。但是这个圆进行分段位移。 也就是分四个部分 分别作不同的位移
这样LINE_LOOP 会为我们连接隔开的部分，形成圆角矩形。
程序代码：
float cirR=20.0,divide=20.0,part=divide/4.0; //cirR是圆角半径，divide是细分程度
glColor3f(0.5,0.5,0.5);
glBegin(GL_LINE_LOOP);
for (i=part*0.0;i<=part*1.0;i+=1.0) {
tx=cirR * cos( ang * i / divide )+20.0;
ty=cirR * sin( ang * i / divide )+20.0;
glVertex3f(tx,ty,0.0);
}
for (i=part*1.0;i<=part*2.0;i+=1.0) {
tx=cirR * cos( ang * i / divide )-20.0;
ty=cirR * sin( ang * i / divide )+20.0;
glVertex3f(tx,ty,0.0);
}
for (i=part*2.0;i<=part*3.0;i+=1.0) {
tx=cirR * cos( ang * i / divide )-20.0;
ty=cirR * sin( ang * i / divide )-20.0;
glVertex3f(tx,ty,0.0);
}
for (i=part*3.0;i<=part*4.0;i+=1.0) {
tx=cirR * cos( ang * i / divide )+20.0;
ty=cirR * sin( ang * i / divide )-20.0;
glVertex3f(tx,ty,0.0);
}
glEnd();
这个看起来有问题 ，衔接线段之间因为偏移产生了锯齿。这个偏移主要还是因为在圆上取点的时候是相邻的。
不过对代码来说是一个简化，在一个循环内算出所有顶点，实现过程有点像分段函数。
程序代码：
glBegin(GL_LINE_LOOP);
for (i=0.0;i<=divide;i+=1.0) {
tx=cirR*cos(6.28*i/divide);
ty=cirR*sin(6.28*i/divide);
if (0.0<=i && i<=5.0) {tx+=10.0;ty+=10.0;}
if (6.0<=i && i<=10.0) {tx-=10.0;ty+=10.0;}
if (11.0<=i && i<=15.0) {tx-=10.0;ty-=10.0;}
if (16.0<=i && i<=20.0) {tx+=10.0;ty-=10.0;}
glVertex3f(tx,ty,0.0);
}
glEnd();
简单的圆角矩形已经没问题了，空心的圆角矩形，在这个基础上做个组合，
在一个循环内计算两组坐标，一组是内矩形，一组是外矩形的坐标，然后用QUAD_STRIP 内外坐标相连接
用四边形组成一个空心圆角矩形，其实直接的说法是是组成了一个环状物。
顶点的连接顺序如图：
这次直接上完整代码，对代码进行了修正，复合了第一个和第二个圆角矩形的方法，封装成函数。
RoundRect.c
程序代码：
/*
Date 2012-04-01
Code by 523066680@ [www.]
改动：对函数代码进行了缩减
*/
#include <stdio.h>
#include <stdlib.h>
#include <GL/glut.h>
#include <time.h>
#include <math.h>
int winid;
void RoundRect(
float divide, //圆角细分数量
float cirr, //内圆角半径
float cirR, //外圆角半径
float w, //内矩形宽度
float h, //内矩形高度
float W, //外矩形宽度
float H) //外矩形高度
{
float halfW=W/2.0,halfH=H/2.0,halfw=w/2.0,halfh=h/2.0;
float part=divide/4.0,tx,ty,i,ang=6.28;
int whois=0;
float arr[4][4]={
halfw,halfh,halfW,halfH,
-halfw,halfh,-halfW,halfH,
-halfw,-halfh,-halfW,-halfH,
halfw,-halfh,halfW,-halfH,
};
glBegin(GL_QUAD_STRIP);
for (i=0.0;i<=divide;) {
tx=cirr * cos( ang * i / divide )+arr[whois][0];
ty=cirr * sin( ang * i / divide )+arr[whois][1];
glVertex3f(tx,ty,0.0);
tx=cirR * cos( ang * i / divide )+arr[whois][2];
ty=cirR * sin( ang * i / divide )+arr[whois][3];
glVertex3f(tx,ty,0.0);
if (whois==0 && i == part*1.0) {whois+=1;i-=1.0;}
if (whois==1 && i == part*2.0) {whois+=1;i-=1.0;}
if (whois==2 && i == part*3.0) {whois+=1;i-=1.0;}
if (whois==3 && i == part*4.0) {whois=0;i-=1.0;} //i积累满时，for结束，为了完成回环，i-=1.0;
i+=1.0;
}
glEnd();
}
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glPushMatrix();
glColor3f(0.5,0.5,0.5);
RoundRect(20.0, 10.0, 20.0, 20.0,50.0, 30.0,35.0);
glPopMatrix();
glutSwapBuffers();
}
void idle(void)
{
usleep(5000);
glutPostRedisplay();
}
void reshape(int Width,int Height)
{
float far=300.0;
glViewport(0,0,500,500);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0,1.0,100.0,900.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0.0,0.0,far, 0.0,0.0,0.0, 0.0,1.0,far);
}
void init(void)
{
glClearColor(0.0,0.0,0.0,0.0);
}
void keypress(unsigned char key,int mousex,int mousey)
{
switch (key) {
case 'q':
glutDestroyWindow(winid);
exit(0);
break;
}
}
int main(int argc,char *argv[])
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB);
glutInitWindowSize(500,500);
glutInitWindowPosition(100,100);
winid=glutCreateWindow("Press - + w a x y R r");
init();
glutReshapeFunc(reshape);
glutDisplayFunc(display);
glutIdleFunc(idle);
glutKeyboardFunc(keypress);
glutMainLoop();
return 0;
}
本人编译环境: MinGW , 编译句gcc RoundRect.c -lglut32 -lglu32 -lopengl32
523066680 @
http://www.
[ 本帖最后由 if_exist 于 2012-4-17 22:30 编辑 ]
