Part of the Khronos Group
OpenGL.org

The Industry's Foundation for High Performance Graphics

from games to virtual reality, mobile phones to supercomputers

Results 1 to 4 of 4

Thread: Plane description and Half Life

  1. #1
    Junior Member Newbie
    Join Date
    Nov 2001
    Location
    Italy
    Posts
    21

    Plane description and Half Life

    Hello to everybody!

    Can someone help me out with the math behind the computation of the 3 points required to describe a plane given face vertices and a normal?
    I need this to write an exporter for my opengl application to Half Life .map file format...

    Thanks in advance!

  2. #2
    Advanced Member Frequent Contributor
    Join Date
    Apr 2000
    Location
    Melbourne,Victoria,Australia
    Posts
    748

    Re: Plane description and Half Life

    I'm not sure I understand. You have the vertices of the face (ie. the corners of your triangle) and the normal and you want to calculate points to describe the plane of that triangle? They're the points of your triangle!

    Or are you trying to calculate the normal for your face (given the three points)?

  3. #3
    Junior Member Newbie
    Join Date
    Nov 2001
    Location
    Italy
    Posts
    21

    Re: Plane description and Half Life

    Yes, but it's not a triangle, usually it has 4 or more vertices... which ones should i take? in which order? why? And why if i export it using face vertices half life editor doesnt open it well? (i think because i cannot use face vertices..)

    Btw, thanks for the reply man!

  4. #4
    Super Moderator OpenGL Lord
    Join Date
    Dec 2003
    Location
    Grenoble - France
    Posts
    5,580

    Re: Plane description and Half Life

    Better to read the docs : http://collective.valve-erc.com/index.php?go=map_format

    "[The three points] must be in a clockwise order when facing the outside of the plane - that is, the side that points outwards from the brush, and these points must lie on the surface of the plane. They must also be different from one another, and not lie on a line - they must form three corners of a triangle when joined up. (Three vertices of the face being represented by this plane will often suffice.)"

    I think you can take the tree first non-colinear points of a polygon.
    A good description of what you will probably need : http://extension.ws/hlfix/technical.html

    [This message has been edited by ZbuffeR (edited 01-06-2004).]

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •