 | | RE: Quad intersections
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| Hi Steve, I've been lurking for a while and thought your post was interesting enough to figure it out. I brushed off my Calculus text book, and after a page and a half of algebra, and remembering what determinants and cross products are all about I (...) (26 years ago, 5-Apr-99, to lugnet.cad.dev)
| | | | | Re: Quad intersections
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| Dave, Thank you very much! This will help me on some parts-work I was avoiding, just because I didn't want to figure out these intersections. I'm planning on uploading a spreadsheet with some basic interpolation and intersection templates. Do you (...) (26 years ago, 5-Apr-99, to lugnet.cad.dev)
| | | | | Re: Quad intersections
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| Based on Dave's formulae, I have been able to calculate the intersection of a plane (given three points) and a line (given two points). How do I then determine whether the point of intersection falls within a quad (as in Dave's "exercise left for (...) (26 years ago, 16-Apr-99, to lugnet.cad.dev)
| | | | | Re: Quad intersections
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| (...) Using quad points Q0 - Q3, point of intersection I. For all lines QmQn, where I.X is between Qm.X and Qn.X, interpolate the point Jmn on QmQn where Jmn.X = I.X. If I.Z is between min(Jmn.Z) and max(Jmn.Z) then I lies within quad Q. If I.Z is (...) (26 years ago, 16-Apr-99, to lugnet.cad.dev)
| | | | | Re: Quad intersections
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| (...) Here's what I use, it works for triangles but you can easily change it for a quad. The idea is to check the angles between the vectors formed by each vertex and the point you're testing. x,y,z: point p1,p2,p3: vertex (float[3]) double pa1[3], (...) (26 years ago, 16-Apr-99, to lugnet.cad.dev)
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