[每日一码] （3）获得AcDbSpline准确的包围盒

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1. ///////////////////////////////////////////////////////////////////////////////////////////////
2. //Description: fKeepExtremes
3. //1) Function to check for the minimum/maximum X and Y.
4. //2) mPtMin and mPtMax will have minimum/maximum X and Y
5. ///////////////////////////////////////////////////////////////////////////////////////////////
8. void fKeepExtremes(AcGePoint3d& mPtSample,AcGePoint3d& mPtMin,AcGePoint3d& mPtMax)
9. {
10. //test for max
11. if(mPtSample.x > mPtMax.x) mPtMax.x = mPtSample.x;
12. if(mPtSample.y > mPtMax.y) mPtMax.y = mPtSample.y;
13. if(mPtSample.z > mPtMax.z) mPtMax.z = mPtSample.z;
15. //test for min
16. if(mPtSample.x < mPtMin.x) mPtMin.x = mPtSample.x;
17. if(mPtSample.y < mPtMin.y) mPtMin.y = mPtSample.y;
18. if(mPtSample.z > mPtMax.z) mPtMax.z = mPtSample.z;
19. }
22. ///////////////////////////////////////////////////////////////////////////////////////////////
23. //Description: fGetBoundingBoxBySampling
24. //1) Function to divide the AcDbSpline 1e6 times and check for points at each division
25. ///////////////////////////////////////////////////////////////////////////////////////////////
26. void fGetBoundingBoxBySampling(AcDbSpline *pSpline,AcGePoint3d& mPtMin, AcGePoint3d& mPtMax)
27. {
28. double mParam;
29. double mIncr;
32. double mStartParam;
33. double mEndParam;
36. AcGePoint3d mPtTemp;
37. pSpline->getStartPoint(mPtTemp);
38. pSpline->getParamAtPoint(mPtTemp,mStartParam);
41. pSpline->getEndPoint(mPtTemp);
42. pSpline->getParamAtPoint(mPtTemp,mEndParam);
44. //calculate the division
45. mIncr = (mEndParam - mStartParam)/1e6; //1e6 is the sampling tolerance
47. //set the seed point for max and min. It is set to the start point
48. mPtMax = mPtTemp;
49. mPtMin = mPtTemp;
52. for(mParam = mStartParam;mParam <= mEndParam;mParam +=mIncr)
53. {
54.   if(Acad::eOk == pSpline->getPointAtParam(mParam,mPtTemp))
55.   {
56.    fKeepExtremes(mPtTemp,mPtMin,mPtMax);
57.   }
60. }
61. }
64. ///////////////////////////////////////////////////////////////////////////////////////////////
65. //Description: fDrawRect
66. //1) Draws a LwPolyline rectangle given lower left and upper right corners
67. ///////////////////////////////////////////////////////////////////////////////////////////////
68. void fDrawRect(AcGePoint3d& mPtMin,AcGePoint3d& mPtMax,int mColor)
69. {
70. AcDbPolyline *pPline = new AcDbPolyline(4);
71. pPline->addVertexAt(0, AcGePoint2d(mPtMin.x,mPtMin.y));
72. pPline->addVertexAt(1,AcGePoint2d(mPtMax.x,mPtMin.y));
73. pPline->addVertexAt(2,AcGePoint2d(mPtMax.x,mPtMax.y));
74. pPline->addVertexAt(3,AcGePoint2d(mPtMin.x,mPtMax.y));
75. pPline->setClosed(Adesk::kTrue);
77. fAddEntToDwg(acdbHostApplicationServices()->workingDatabase(),pPline);
78. pPline->setColorIndex(mColor);
79. pPline->close();
80. }
83. ///////////////////////////////////////////////////////////////////////////////////////////////
84. //Description: SplineBB
85. //1) command 'SplineBB'
86. ///////////////////////////////////////////////////////////////////////////////////////////////
87. void SplineBB()
88. {
89. AcDbEntity *pEnt = NULL;
90. AcDbObjectId mId;
91. ads采用point mPt;
92. ads采用name mEname;
94. //select the entity
95. if ( RTNORM == acedEntSel(L"Select a Spline", mEname, mPt))
96. {
97.   if ( Acad::eOk == acdbGetObjectId(mId, mEname ))
98.   {
99.    acdbOpenAcDbEntity(pEnt, mId, AcDb::kForRead);
100.   }
101. }
102. else
103. {
104.   return;
105. }
108. //see if it is a spline
109. AcDbSpline *pSpline = NULL;
112. if (NULL != pEnt)
113. {
114.   pSpline = AcDbSpline::cast(pEnt);
117.   if(NULL != pSpline)
118.   {
119.    AcGePoint3d mPtMin,mPtMax;
122.    //draw the bounding box returned by spline's getGeomExtents
123.    AcDbExtents mExts;
124.    pSpline->getGeomExtents(mExts);
127.    //draw bounding box returned by the spline in red
128.    fDrawRect(mExts.minPoint(),mExts.maxPoint(),1);
130.    //calculate the time taken
131.    struct 采用timeb t1,t2;
132.    采用ftime(&t1);
135.    //calculate the bounding box
136.    fGetBoundingBoxBySampling(pSpline,mPtMin,mPtMax);
138.    采用ftime(&t2);
139.    acutPrintf(L"\nMethod Time %6.2f seconds.\n", (t2.time + (double)(t2.millitm)/1000) - (t1.time + (double)(t1.millitm)/1000) );
141.    //draw calculated bounding box in yellow
142.    fDrawRect(mPtMin,mPtMax,2);
145.    pSpline->close();
146.   }
147.   else
148.   {
149.    acutPrintf(L"\nEntity is not an Spline");
150.    pEnt->close();
151.   }
152. }
153. return;
154. }

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admin

1. 这个代码用的是模拟点法计算包围盒，还是不太精确，计算量也比较大！
2. 我写的这个既精确又快！
3. 普通浏览复制代码
4. void getSplineBox (const AcDbSpline *pSpline,AcGePoint3d &minPt,AcGePoint3d &maxPt)
5. {
6.         AcDbExtents Ext;
7.         AcGePoint3d p0,p1,p2,p3;
8.         AcDbIntArray osnapModes,geomIds;
9.         AcGePoint3dArray pt3ds;
10.         pSpline->getGripPoints(pt3ds,osnapModes,geomIds);
11.         for (int k = 0;k<pt3ds.length();k++)
12.         {
13.                 Ext.addPoint(pt3ds.at(k));
14.         }
15.         p0 = Ext.minPoint();
16.         p2 = Ext.maxPoint();       double dis = 0.5 * (p2-p0).length();
17.         p0.x = p0.x - dis;
18.         p0.y = p0.y - dis;
19.         p2.x = p2.x + dis;
20.         p2.y = p2.y + dis;
21.         p1.x = p0.x;
22.         p1.y = p2.y;
23.         p1.z = p0.z;
24.         p3.x = p2.x;
25.         p3.y = p0.y;
26.         p3.z = p2.z;
27.         AcGeVector3d vec0(1.0,0.0,0.0),vec1(0.0,-1.0,0.0),vec2(-1.0,0.0,0.0),vec3(0.0,1.0,0.0);
28.         pSpline->getClosestPointTo(p0,vec0,p0,Adesk::kTrue);               
29.         pSpline->getClosestPointTo(p1,vec1,p1,Adesk::kTrue);
30.         pSpline->getClosestPointTo(p2,vec2,p2,Adesk::kTrue);
31.         pSpline->getClosestPointTo(p3,vec3,p3,Adesk::kTrue);
32.         AcDbExtents Ext1;
33.         Ext1.addPoint(p0);
34.         Ext1.addPoint(p1);
35.         Ext1.addPoint(p2);
36.         Ext1.addPoint(p3);
37.         minPt = Ext1.minPoint();
38.         maxPt = Ext1.maxPoint();
39. }

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admin

G 版用的是这个函数

AcDbCurve::getClosestPointTo 函数

virtual Acad::ErrorStatus
getClosestPointTo(
const AcGePoint3d& givenPnt,
const AcGeVector3d& direction,
AcGePoint3d& pointOnCurve,
Adesk::Boolean extend = Adesk::kFalse) const;

givenPnt 输入点（WCS坐标中），用于找出曲线上的最近点
direction 输入法向矢量（WCS坐标中），用于平面投影
pointOnCurve 返回曲线上与givenPnt最近的点（WCS坐标中）
extend 输入布尔值，表示在搜索最近点时是否延伸曲线

此函数将曲线投影至由givenPnt和normal定义的平面，找出曲线上与givenPnt最近的点，再将这个最近点投影回原始曲线上并在pointOnCurve中返回结果。

如果extend == Adesk::kTrue，则曲线沿它的路径延伸以找出最近点。

如果成功则返回Acad::eOk。根据执行返回错误值。

在派生类中，此函数必须可以投影至由一个点（givenPnt）和一个法向矢量(normal)定义的平面上，如果需要可延伸曲线的投影，找出与givenPnt最近的点，再将这个找到的点投影回原始曲线上（如果被延伸则在它的路径上）并设置pointOnCurve为最终结果。

使用AcGe类可执行一些投影和最近点计算的工作。

如果操作成功，此函数返回Acad::eOk。错误的返回值根据错误和执行器。关于可能的ErrorStatus值列表，参见头文件acdh.h。

默认执行返回Acad::eNotImplemented。


先用一个较大方框作投影面，用函数找出曲线上距离投影面最近的点，四个边就求出四个点，然后由这四个点载找个 BOX

vlisp 对应函数是

在将曲线投影到平面上之后，返回曲线上的最近点（在 WCS 上）

(vlax-curve-getClosestPointToProjection curve-obj givenPnt normal[extend])
参数

curve-obj  要测量的 VLA 对象。
givenPnt   WCS 中的点，在曲线上寻找该点的最近点。
normal   WCS 中的法线矢量，指定投影平面。
extend   如果指定该参数且其值不为 nil，vlax-curve-getClosestPointToProjection 在搜索最近点时扩展曲线。

vlax-curve-getClosestPointToProjection 将曲线投影到由 givenPnt 和 normal 定义的平面上，然后在该平面上计算距 givenPnt 最近的点。然后，vlax-curve-getClosestPointToProjection 将结果点重新投影到原来的曲线上，并返回投影后的点。

返回值   如果成功，则返回表示曲线上一点的三维点表，否则返回 nil。