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Re: Check if a point is inside a polygon mesh [message #45232 is a reply to message #45231]

Thu, 18 August 2005 09:10

Karl Schultz
Messages: 341
Registered: October 1999

Senior Member

On Thu, 18 Aug 2005 03:53:19 -0700, photosalex@freenet.de wrote:

> Hello, All!
>
> Does anybody know a way to figure out if a 3D point lies inside a
> closed 3D triangular polygon mesh. The mesh is a tricky engineering
> construction of thousands of vertices with holes, stems, supports etc.,
> rather than a rectangular slab.
>
> The question arose basically from the task to find the coordinates of
> the intersection(s) of a ray with an arbitrary volumetric IDL model.
> I've searched the newsgroups but couldn't find a ready answer.
>
> If anyone provides me with information on either problems, I'd be very
> grateful.
>
> Cheers!

One way to do it is to create a point that you know is outside of the
mesh. Use that point and the point in question to define a line segment.
Then, perform a simple triangle/line-segment intersection check for each
triangle in the mesh and keep track of the number of times the line
intersects a triangle. If the total number of intersections is odd, the
point in question is considered to be inside the closed mesh.

Karl

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[Message index]

		Re: Check if a point is inside a polygon mesh By: Rick Towler on Mon, 22 August 2005 14:16
		Re: Check if a point is inside a polygon mesh By: cartik.sharma on Thu, 18 August 2005 18:32
		Re: Check if a point is inside a polygon mesh By: Karl Schultz on Thu, 18 August 2005 09:10

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