How come objects farther away are showing through closer objects
(aka bleed throughs)?
Not to be confused with the
Z buffer 'miniblinds flickering effect', this is due
to depth testing intentionally turned off for certain objects
that are impossible to be displayed with OpenGL properly.
Technical note, this problem is caused by the need to render objects
such as heighfields over flat 2D surfaces where parts of the heightfield
are parallel and at the exact height of the 2D surface. Enabling
OpenGL's polygon offset is not a solution as the written depth would
otherwise be incorrect. There is a high
performance cost solution to this using two passes and OpenGL's stencil
buffer, however it is not a viable solution at this time (Oct 2001).
Reffer back to this section in the future, a solution may be available
then.
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Why do some parts of the scene seem to flicker like
miniblinds (aka miniblinds flickering effect)?
Most objects drawn over other objects in perfect parallel alignment
and at the same location will 'fight' to show though in the
depth buffer. This causes a miniblinds flickering effect, the solution
is to use a technique called polygon offsetting which this application
uses when appropriate.
However some systems have differences in the amount of offsetting
so sometimes the user needs to adjust this value. You can change this
value in game by pressing the /
key to bring up the
prompt and then type in option gl_polgyon_offset=-2.0
A typical value can be from -1.5
to -2.0
where the more negative value produces more offset. Reduce (make more
negative) this value if you are still getting a lot of
miniblinds flickering effect. Note that this changed value will be
stored in your SearchAndRescue.ini
file.
Some scenerys are partially responsible for denoting where
to use polygon offsetting and that the scenery builder/author may need
to be nofitied about the problem if specifying a lower
gl_polgyon_offset
value does not work. If you try going below
-10.0
without any good results, then that might indicate
it is a problem with the scenery.
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How do I recompile with debugging support and debug the program?
(UNIX/X version only) go back to the source directory for this program
(or download it again if you deleted it) and type the following
command on your shell prompt
(you may have to replace some values to suit your system):
./configure linux -v --prefix=/usr --enable="debug"
--disable="arch-i586"
The above command assumes you are using Linux and that your computer is
an Intel Pentium 586 (i586). If you have a 486, then change
arch-i586
to arch-i486
. Use the command
uname -m
to find out which one you have.
If the source (re)configuration worked, then type
If everything was successful then you can begin the debugging
process (this assumes you've already ran make install
earlier). Run gdb sar/SearchAndRescue
, this will run
the GNU Debugger (gdb). Once you are in gdb, type run
to run the program. When/if the program crashes, type bt
to display the backtrace. Besure to send the backtrace to
the authors as needed. Type quit
to quit gdb, note that gdb
will ask if you want to quit while the program crashed but is still
running. Say yes to that.
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