[图形学]Chapter 8.7.2 梁友栋-Barsky线段裁剪算法

 1 #include <GLUT/GLUT.h>
 2 #include <iostream>
 3 #include "lineliangbarsk.h"
 4 #include "linebres.h"
 5 
 6 GLint clipTest (GLfloat p, GLfloat q, GLfloat * u1, GLfloat * u2)
 7 {
 8     GLfloat r;
 9     GLint returnValue = true;
10     
11     if(p < 0.0)
12     {
13         r = q / p;
14         if(r > *u2)
15         {
16             returnValue = false;
17         }
18         else
19         {
20             if(r > *u1)
21             {
22                 *u1 = r;
23             }
24         }
25     }
26     else
27     {
28         if(p > 0.0)
29         {
30             r = q / p;
31             if(r < *u1)
32             {
33                 returnValue = false;
34             }
35             else
36             {
37                 if(r < *u2)
38                 {
39                     *u2 = r;
40                 }
41             }
42         }
43         else
44         {
45             if(q < 0.0)
46             {
47                 returnValue = false;
48             }
49         }
50     }
51     return returnValue;
52 }
53 
54 void lineClipLiangBarsk(wcPt2D winMin, wcPt2D winMax, wcPt2D p1, wcPt2D p2)
55 {
56     GLfloat u1 = 0.0, u2 = 1.0, dx = p2.getx() - p1.getx(), dy;
57     
58     if(clipTest(-dx, p1.getx() - winMin.getx(), &u1, &u2))
59     {
60         if(clipTest(dx, winMax.getx() - p1.getx(), &u1, &u2))
61         {
62             dy = p2.gety() - p1.gety();
63             if(clipTest(-dy, p1.gety() - winMin.gety(), &u1, &u2))
64             {
65                 if(clipTest(dy, winMax.gety() - p1.gety(), &u1, &u2))
66                 {
67                     if(u2 < 1.0)
68                     {
69                         p2.setCoords(p1.getx() + u2 * dx, p1.gety() + u2 * dy);
70                     }
71                     if(u1 > 0.0)
72                     {
73                         p1.setCoords(p1.getx() + u1 * dx, p1.gety() + u1 * dy);
74                     }
75                     lineBres(round(p1.getx()), round(p1.gety()), round(p2.getx()), round(p2.gety()));
76                     std::cout << "liangbarsk : " << u1 << "," << u2 << std::endl;
77                     std::cout << "liangbarsk : " << p1.getx() << "," << p1.gety() << "," << p2.getx() << "," << p2.gety() << std::endl;
78                 }
79             }
80         }
81     }
82 }