Benito Graniela (graniela++at++vsl.ist.ucf.edu)
Mon, 20 Mar 1995 08:32:21 -0500
We are still struggling with co-planar planes and z-buffering in our
application. In our database the roads are co-planar with the terrain.
These causes the roads to be "Z fighting" or "flimmering" like the man
pages describe them.
Ran, we have tried to setup stencils using the stensize() command with no
difference in the behavior of our application. Maybe we are not inserting
the calls in the right place? Can you more specific as to were this command
should be placed within the program.
Allan, we are staying away from "stitching" the road polygons because it
will have to be done manually and there is a lot of roads, rail roads,
rivers and other networks. Maybe somebody out there has an algorithm that
will implement this "stitching" function. The algorithm will replace the
terrain polygons with road polygons, however this is not a trivial task so
we are also staying away from developing such algorithm.
Angus, we are also staying away from modifying the z-buffer before and after
drawing the road polygons because we are running on an Indigo Extreme and
it will kill our frame rate (15 Hz).
The best solution so far is being to label the roads as subfaces. This
has taken care of the "shimmering" polygons but it has created another
rendering anomalies. Some times depending on the angle and view point
location roads can be seen through hills and buildings. The only changes
here is to the database, and the anomalies can be seen using Perfly. We
have tried stensize() calls but they do not seam to make any difference.
Can anybody explain what Performer is doing when it sees this sub-face
polygons and why we are seen this rendering anomalies.
We have placed a copy of the database in our anonymous ftp site for all of
those that will like to take a look at these anomalies and maybe suggest a
fix to this problem. The database can be viewed with Perfly or any other
program the will load a Flight 14.X format database.
The ftp site is "ftp.vsl.ist.ucf.edu" and the files are in the following
directory:
/pub/vtb/graf_tdb
There are two files in there:
terrain.tar.Z and
terrain.uu
The terrain.tar.Z is a UNIX LZW compressed tar file of the database
and terrain.uu is a uuencoded version of file terrain.tar.Z.
Please feel free to ftp the database or let me know if you will like
me to e-mail it to you.
thanks
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Benito Graniela University of Central Florida
Visual Systems Lab Institute for Simulation & Training
(407) 658-5075 3280 Progress Drive
bgraniela++at++vsl.ist.ucf.edu Orlando, FL 32806-0544
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