相交测试

Berly

做相交测试的时候，做了同样的碰撞检测，模型对称的，为什么一个是红色，一个是绿色呢？（条件：有交点显示红色三角形，没有交点为绿色）图上都应该没有交点，应该都是红色的。各位大师指点

gis_wudi

这个问题最好的解决方式就是跟代码

Berly

gis_wudi 发表于 2012-11-20 13:41
这个问题最好的解决方式就是跟代码

1. 
   
2. void getIntersections( osg::Vec3dArray *buttomPointList,osg::Group* sphereGroup, osg::Node* model, osg::Vec3d p_start,osg::Vec3d p_end)
   
3. {
   
4. osg::ref_ptr< osgUtil::LineSegmentIntersector > _lineSegmentIntersector = new osgUtil::LineSegmentIntersector(p_start,p_end);
   
5. osgUtil::IntersectionVisitor _iv(_lineSegmentIntersector.get());
   
6. model->accept(_iv);
   
7. 
   
8. osgUtil::LineSegmentIntersector::Intersections _intersections = _lineSegmentIntersector->getIntersections();
   
9. int _intersectionNumber=_intersections.size();
   
10. osgUtil::LineSegmentIntersector::Intersections::iterator hitr = _intersections.begin();
    
11. for (; hitr != _intersections.end();hitr++)
    
12. {
    
13. buttomPointList->push_back(hitr->getWorldIntersectPoint());
    
14. }
    
15. for (int i=0;i<buttomPointList->size();i++)
    
16. {
    
17. osg::Geode* geode=new osg::Geode;
    
18. osg::ShapeDrawable *viewPoint=new osg::ShapeDrawable(new osg::Sphere(buttomPointList->at(i),0.01f));
    
19. viewPoint->setColor(osg::Vec4(0.0f,0.0f,1.0f,1.0f));
    
20. geode->addDrawable(viewPoint);
    
21. sphereGroup->addChild(geode);
    
22. }
    
23. }
    
24. osg::ref_ptr<osg::Group>getVisiableRange(osg::Vec3d eyePoint,osg::Vec3dArray* buttomList,osg::Node *model,float gre,float yel,float red)
    
25. {
    
26. osg::ref_ptr<osg::Group>visiableRange=new osg::Group;
    
27. osg::Vec4 colorGre=osg::Vec4(0.0f,1.0f,0.0f,gre);
    
28. osg::Vec4 colorYel=osg::Vec4(1.0f,1.0f,0.0f,yel);
    
29. osg::Vec4 colorRed=osg::Vec4(1.0f,0.0f,0.0f,red);
    
30. 
    
31. for (int i=0;i<buttomList->size()-1;i++)
    
32. {
    
33. osg::ref_ptr<osg::Group>group=new osg::Group;
    
34. osg::ref_ptr<osg::Group>group2=new osg::Group;
    
35. osg::ref_ptr<osg::Group>geodeGre=new osg::Group;
    
36. osg::ref_ptr<osg::Group>geodeYel=new osg::Group;
    
37. osg::ref_ptr<osg::Group>geodeRed=new osg::Group;
    
38. osg::ref_ptr<osg::Vec3dArray>pointArrYel=new osg::Vec3dArray;
    
39. osg::ref_ptr<osg::Vec3dArray>pointArrRed=new osg::Vec3dArray;
    
40. osg::ref_ptr<osg::Vec3dArray> pointArrGre=new osg::Vec3dArray;
    
41. osg::Vec3d end=buttomList->at(i);
    
42. osg::Vec3dArray* hitList=new osg::Vec3dArray;
    
43. getIntersections(hitList,group,model,eyePoint,end);
    
44. 
    
45. osg::Vec3d end2=buttomList->at(i+1);
    
46. osg::Vec3dArray* hitList2=new osg::Vec3dArray;
    
47. getIntersections(hitList2,group2,model,eyePoint,end2);
    
48. 
    
49. cout<<"hitList:--"<<hitList->size()<<"hitList2:--"<<hitList2->size()<<endl<<endl;
    
50. //||((end-hitList->at(0)).length()<0.1&&(end2-hitList2->at(0)).length()<0.1)||((eyePoint-hitList->at(0)).length()<0.1&&(eyePoint-hitList2->at(0)).length()<0.1)
    
51. if (hitList->size()==0 && hitList2->size()==0)
    
52. {
    
53. pointArrGre->push_back(eyePoint);
    
54. pointArrGre->push_back(end);
    
55. pointArrGre->push_back(end2);
    
56. }
    
57. if (hitList->size()==0&&hitList2->size()!=0)
    
58. {
    
59. osg::Vec3d visiablePoint2=hitList2->at(0);
    
60. pointArrYel->push_back(eyePoint);
    
61. pointArrYel->push_back(end);
    
62. pointArrYel->push_back(visiablePoint2);
    
63. pointArrRed->push_back(visiablePoint2);
    
64. pointArrRed->push_back(end);
    
65. pointArrRed->push_back(end2);
    
66. }
    
67. else if (hitList->size()!=0&&hitList2->size()==0)
    
68. {
    
69. osg::Vec3d visiablePoint=hitList->at(0);
    
70. pointArrYel->push_back(eyePoint);
    
71. pointArrYel->push_back(visiablePoint);
    
72. pointArrYel->push_back(end2);
    
73. 
    
74. pointArrRed->push_back(visiablePoint);
    
75. pointArrRed->push_back(end);
    
76. pointArrRed->push_back(end2);
    
77. }
    
78. else
    
79. {
    
80. osg::Vec3d visiablePoint=hitList->at(0);//(hitList->at(1)-hitList->at(0)).length()<0.2?hitList->at(1):
    
81. osg::Vec3d visiablePoint2=hitList2->at(0);//(hitList2->at(1)-hitList->at(0)).length()<0.2?hitList2->at(1):
    
82. pointArrYel->push_back(visiablePoint);
    
83. pointArrYel->push_back(visiablePoint2);
    
84. pointArrRed->push_back(visiablePoint);
    
85. pointArrRed->push_back(end);
    
86. pointArrRed->push_back(end2);
    
87. pointArrRed->push_back(visiablePoint2);
    
88. }
    
89. geodeYel->addChild(getPoly(pointArrYel,colorYel));
    
90. geodeRed->addChild(getPoly(pointArrRed,colorRed));
    
91. geodeGre->addChild(getPoly(pointArrGre,colorGre));
    
92. 
    
93. visiableRange->addChild(geodeYel);
    
94. visiableRange->addChild(geodeRed);
    
95. visiableRange->addChild(geodeGre);
    
96. visiableRange->addChild(group);
    
97. visiableRange->addChild(group2);
    
98. }
    
99. 
    
100. // break;
     
101. return visiableRange;
     
102. 
     
103. }

复制代码

osg::ref_ptr< osg::Vec3dArray> buttomList  =  new osg::Vec3dArray;
       buttomList->push_back(start);
       osg::ref_ptr<osg::Group>group=new osg::Group;
       getIntersections(buttomList,group,modelGroup,start,end);
       buttomList->push_back(end);
        cout<<"buttomPointList Size"<<buttomList->size()<<endl<<endl;
       viewer->getSceneData()->asGroup()->addChild(getVisiableRange( eyePoint,buttomList,modelGroup,0.2,0.2,0.2));
这个是handle()调用的上面函数的部分。
上面第一个函数：getIntersections()是求的交点的函数，使用lineSegmentIntersector;
第二个函数：getVisiableRange()是获得可是范围多边形的函数，分为四种情况：1）两条边都没有交点，直接可视，用绿色三角形表示；2）左边没有交点，右边有交点，取第一个交点作为可视与不可视的划分，该交点的前部分用黄色三角形表示，后部分用红色三角形；3）同2）条件相反；4）两条边都有交点，分别取第一个交点作为划分，黄色三角形为可见部分，红色的（应该是梯形）为不可见部分。

我还没有找到哪里错了，但是结果不对，各位人才，帮忙看看吧，拜谢……

array

最大的可能性就是您的线段起点或终点正好和物体相交，但是因为float类型精度的问题，这个相交的判断可能会失败，把start和end都适当沿着线段方向延长就可以了

Berly

array 发表于 2012-11-22 17:15
最大的可能性就是您的线段起点或终点正好和物体相交，但是因为float类型精度的问题，这个相交的判断可能会失 ...

那个起点和终点确实在物体上，因为起点和终点也是经过碰撞确定的。我换成double也不行，所以有就加了距离判断，如果和起点或终点的距离小于某个值，这个点就不算。但是我一直不明白，他到底算不算终点，如果按照我说的，起始点都是物体上的点，那么碰撞得到的intersections就应该直接包括起始点，可是有很多时候都没有包括。
2）还有个问题，碰撞的线段的起始点都在同一个平面上都有可能出现交点（非起始点的交点），为什么呢？

array

1、难道您真的不知道计算机的float类型从来都不准确么。。。换成double是没用的因为Intersector内部依然用float来计算，我说的延长线的方法是最直接的也是最准确的

2、为什么您认为没有