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Re: point inside/outside of 3D object. [message #76626 is a reply to message #76567]

Tue, 21 June 2011 02:24

Wout De Nolf
Messages: 194
Registered: October 2008

Senior Member

On Sat, 18 Jun 2011 11:34:42 -0700 (PDT), Junum <junshikum@gmail.com>
wrote:

> Thanks Karl.
> I wanted know whether IDLanROI::ContainsPoints can be applied to 3D
> case.

I'd guess the answer is no. You should implement this yourself (as
Karl suggested) or you could do something like below. I'm not sure
whether this is the best way, but it seems to work.

; Generate vertices
v=TetrahedronVertices(r=10,phideg=-20)

; Connectivity list: [n,i[0],...,i[n-1],n,j[0],...,j[n-1],...]
; n: number of vertices for each face
; i[0],...,i[n-1]: vertices for face 1, ordered so that the normal
; points outwards (right-hand rule)
; j[0],...,j[n-1]: vertices for face 2, ordered so that the normal
; points outwards (right-hand rule)
conn=[3,0,3,1, 3,0,1,2, 3,0,2,3, 3,1,3,2]

; Remark: if the number of vertices > 4 then you could generate
; the list like this:
;Qhull, v, tr, /delaunay
;conn=tetra_surface(v, tr)

; Point
p=[0,0,0.]

; Volume of the polyhedron
volume=tetra_volume(v,conn)

; Expanded polyhedron (including your point)
; vertices and connectivity list
v2=[[v],[p]]
Qhull, v2, tr, /delaunay
conn2=tetra_surface(v2, tr)

; Volume of the expanded polyhedron
volumeexp=tetra_volume(v2,conn2)

; If the "expanded volume" is larger, the point lies outside
if volumeexp gt volume then print,'Exterior' else print,'Interior'

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[Message index]

		point inside/outside of 3D object. By: Junum on Tue, 14 June 2011 12:01
		Re: point inside/outside of 3D object. By: Junum on Tue, 21 June 2011 10:22
		Re: point inside/outside of 3D object. By: Karl[1] on Tue, 21 June 2011 08:18
		Re: point inside/outside of 3D object. By: Wout De Nolf on Tue, 21 June 2011 02:24
		Re: point inside/outside of 3D object. By: Guneshwar Thangjam on Sat, 04 July 2015 12:55
		Re: point inside/outside of 3D object. By: Wout De Nolf on Tue, 21 June 2011 01:52
		Re: point inside/outside of 3D object. By: Karl[1] on Mon, 20 June 2011 12:57

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