Re: determining visible points

• To: Raymond Zeigler <raymond@xxxxxxxxxxx>
• Subject: Re: determining visible points
• From: "From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>" <billh@xxxxxxxxxxxxx>
• Date: Mon, 13 Aug 2001 16:34:09 -0500 (CDT)

Hi Raymond,

Determining visibility of points in a terrain plot is a bit
tricky, and I don't think picking logic will help much.

You could use the Java3D Transform to transform the data
coordinates of your points into 3-D (x, y, z) screen
coordiantes, then for each point see if there is a point
at the same approximate x with smaller z (i.e., closer)
and larger y (i.e., higher and thus obscuring). The x test
has to be approximate since your points won't fall on neat
rows and columns once transformed into 3-D screen coords.

Note that a point might also be technically visible (from
underneath the terrain surface) if all the points in front
of it in z have larger y.

Good luck,
Bill
----------------------------------------------------------
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
http://www.ssec.wisc.edu/~billh/vis.html

• References:
  • determining visible points
    • From: Raymond Zeigler