Topic: [AcBr LIB(3)]Find the closest point from a spatial point to each face of 3DSOLID

[xdcad]

question:

I have a point in 3D space and I would like to get the closest point on a 3D solid from this input point. Is there any API to achieve this?


Which API can solve the problem of the closest input point to 3DSOLID?

solution:


It is possible to realize that using the BRep API (located in the <ObjectARX 2009 Path>\utils\brep directory): you need to traverse all the faces that are contained in your 3D solid and for each face use the AcBrFace::getFace method. It returns an AcGeSurface object from where you can use AcGeSurface::closestPointTo, passing in your input point.


Using the BRep API, you need to iterate through all the faces contained in the 3D entity and use the AcBrFace::getFace method for each face to get the AcGeSurface object, and use AcGeSurface::closestPointTo to get the closest point between the input point and the AcGeSurface object.



Here is the ARX code:

Code - C++: [Select]

1. static AcBr::ErrorStatus TraverseFaces(const AcBrBrep& brepEntity, const AcGePoint3d& pointToTest)
2. {
3.         AcBr::ErrorStatus returnValue = AcBr::eOk;
4.         // make a global face traverser
5.         AcBrBrepFaceTraverser brepFaceTrav;
6.         returnValue = brepFaceTrav.setBrep(brepEntity);
7.         if (returnValue != AcBr::eOk)
8.         {
9.                 acutPrintf(ACRX_T("\n Error in AcBrBrepFaceTraverser::setBrep:"));
10.                 errorReport(returnValue);
11.                 return returnValue;
12.         }
13.         int faceCount = 0;
14.        while (!brepFaceTrav.done() && (returnValue == AcBr::eOk))
15.         {
16.                 ++faceCount;
17.                 AcBrFace face;
18.                 if (brepFaceTrav.getFace(face) == AcBr::ErrorStatus::eOk)
19.                 {
20.                         AcGeSurface* pSurface;
21.                         if (face.getSurface(pSurface) == AcBr::ErrorStatus::eOk)
22.                         {
23.                                 AcGePoint3d closestPoint = pSurface->closestPointTo(pointToTest);
24.  
25.                                 double dist = AcGeVector3d(closestPoint.asVector() - pointToTest.asVector()).length();
26.  
27.                                 acutPrintf(L"\n - Face[%d]: closest point [%f, %f, %f]   Distance: %f", faceCount, closestPoint.x, closestPoint.y, closestPoint.z, dist);
28.  
29.                                 delete pSurface;
30.                         }
31.                 }
32.                 returnValue = brepFaceTrav.next();
33.                 if (returnValue != AcBr::eOk) {
34.                         acutPrintf(ACRX_T("\n Error in AcBrBrepFaceTraverser::next:"));
35.                         errorReport(returnValue);
36.                         return returnValue;
37.                 }
38.         }
39.         return returnValue;
40. }
41. void TestClosestPoint(void)
42. {
43.         AcBr::ErrorStatus returnValue = AcBr::eOk;
44.         Acad::ErrorStatus acadReturnValue = eOk;
45.         AcGePoint3d pointToTest;
46.         // pick a point
47.         acedGetPoint(NULL, L"\nPick a point: ", asDblArray(pointToTest));
48.         // Get the subentity path for a brep
49.         AcDbFullSubentPath subPath(kNullSubent);
50.         acadReturnValue = selectEntity(AcDb::kNullSubentType, subPath);
51.         if (acadReturnValue != eOk)
52.         {
53.                 acutPrintf(ACRX_T("\n Error in getPath: %d"), acadReturnValue);
54.                 return;
55.         }
56.         // Make a brep entity to access the solid
57.         AcBrBrep brepEntity;
58.         returnValue = ((AcBrEntity*)&brepEntity)->set(subPath);
59.         if (returnValue != AcBr::eOk)
60.         {
61.                 acutPrintf(ACRX_T("\n Error in AcBrBrep::set:"));
62.                 errorReport(returnValue);
63.                 return;
64.         }
65.         returnValue = TraverseFaces(brepEntity, pointToTest);
66.         if (returnValue != AcBr::eOk)
67.         {
68.                 acutPrintf(ACRX_T("\n Error in TraverseFaces:"));
69.                 errorReport(returnValue);
70.                 return;
71.         }
72. }
73.  

Next, use the ACBR library function of the XDRX API to complete the same work as ARX above.

Code - Auto/Visual Lisp: [Select]

1. (defun c:tt ()
2.    (defun _traversface (e pnt)
3.      (setq br (xdbr::constructor e))
4.      (setq tr (xdbr::constructor "brepfacetraverser" br))
5.      ;;FACE traversal
6.      (setq face-count 0)
7.      (xdrx_entity_delete co-ss)
8.      (xdrx_setmark)
9.      (while (not (xdbr::traverser:done tr)); loop traversal
10.        (if (setq face (xdbr::getpropertyvalue tr "face"));;AcBrFace object
11.          (progn (setq face-count (1+ face-count)
12.                       gface (xdbr::getpropertyvalue face "surface") ;;Get AcGeSurface object
13.                       closest-pnt (xdge::getpropertyvalue gface "closestpointto" pnt);;closest point
14.                       dist (distance pnt closest-pnt)
15.                 )
16.            (xdrx_object_release gface face);;Release AcBrFace, AcGeSurface
17.            (xdrx_point_make closest-pnt)
18.            (xdrx_entity_setcolor (entlast) 2)
19.            (xdrx_line_make pnt closest-pnt)
20.            (xdrx_entity_setcolor (entlast) 1)
21.                 (xdrx_prompt
22.                   (xdrx_string_format "\n - Surface [%d]: nearest point [%f, %f, %f] distance %f"
23.                                       face-count
24.                                       (car closest-pnt)
25.                                       (cadr closest-pnt)
26.                                       (caddr closest-pnt)
27.                                       dist
28.                   )
29.                 )
30.          )
31.        )
32.        (setq co-ss (xdrx_getss))
33.        (xdbr::traverser:next tr)
34.      )
35.      (xdrx_object_release tr br)
36.    )
37.    (if (setq e (car (xdrx_entsel "\nSelect 3DSOLID<Exit>:" '((0 . "3DSOLID")))))
38.      (progn
39.        (xdrx_begin)
40.        (xdrx_sysvar_push '("osmode" 512))
41.        (xdrx_setvar "pdmode" 35)
42.        (while (setq pt (getpoint "\nClick to get the test point <exit>:"))
43.        (_traversface e (setq pt (trans pt 1 0))))
44.        (xdrx_end)
45.      )
46.    )
47.    (princ)
48. )
49.  

The above LISP code uses the XDRX-API, which can be downloaded from https://github.com/xdcad/XDrx-API

The XDRX API encapsulates AcDb, AcEd, AcGe, AcBr... C++ library, using C++ methods to develop LISP programs.Thousands of Lisp functions are available.