Re: Crossing between PATCH and plane

Eric Carlson ha scritto:
Gabriele wrote:
Hi all,
I have the following problem...I have a 3D object, defined by a patch structure, and I want to obtain the intersection between these object and a planar surface. Actually the object could be concave and it is a closed solid, thus multi-valued: I cannot rotate it in any way so to use GRIDDATA and then CONTOUR.

Any idea? Is there something around available or should I start writing it...take a triangle, find intersections, go to the next one...and so and so...??

Thank you in advance...
Bye,
Gab

Hello Gab,

To the best of my knowledge, which admittedly is far from vast, there is 

[...]


The issue of boolean combinations of triangulated surfaces is one that I plan to investigate this year if I ever get a large enough time block.

Cheers,
Eric Carlson

Hi eric,
thank you for your reply.
The actual problem is a patch describing a ship hull. I need a polygonal description of the waterplane area, given a certain draft, in order to estimate a series of properties (area, center, moments of inertia, and so on). Actually the best solution would be something like a function that, given a patch and a series of parameters identifying the plane, will return a polygonal curve defining the intersection. Depending on the shape of the hull, there could be more than 1 closed polygons, due to the fact that the hull can be concave.
There is a way out for this, represented by a sort of trick. I can generate a grid of point all lying on the plane, and then I could separate points that are inside from points that are outside the hull...this would give me a discrete approximation of the area of the waterplane, from which I can calculate almost everything by discrete integration.
If the first more elegant way is not viable, is there something like INPOLYGON but for closed patches? A function returning 0 if the point is outside the solid, or 1 if it is inside the solid? (my patches are ALWAY close solids...)...Otherwise I could try writing it...of course...

Bye,
Gab


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