Subject:
|
Re: Quad intersections
|
Newsgroups:
|
lugnet.cad.dev
|
Date:
|
Fri, 16 Apr 1999 17:35:09 GMT
|
Viewed:
|
1774 times
|
| |
|
|
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 the reader")?
-John Van
Dave Hylands wrote in message
<snip>
> Of course, now that you've found y, you probably need to verify that (x, y,
> z) actually falls within the given quad (as they say in the textbooks, this
> is an exercise left for the reader).
>
> If anyone is interested in a more detailed derivation, I'd be happy to share
> the gory details.
>
|
|
Message has 2 Replies:
 | | Re: Quad intersections
|
| (...) 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 (...) (27 years ago, 16-Apr-99, to lugnet.cad.dev)
| | | Re: Quad intersections
|
| (...) 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], (...) (27 years ago, 16-Apr-99, to lugnet.cad.dev)
|
Message is in Reply To:
| | RE: Quad intersections
|
| 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 (...) (27 years ago, 5-Apr-99, to lugnet.cad.dev)
|
5 Messages in This Thread:
 
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
This Message and its Replies on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|
