[gl4java-usergroup] RE: animation stutters

[Peter <kaf...@xt...>]

> Hi Peter,
> 
> Here is a little checklist that might help you solving your problem :
> 
> Your animation may be stuttering because of frequent runs of the
garbage
> collector. This can happen if you create and destroy a lot of objects
per
> frame. To avoid this, make sure you never create any temporary objects
in
> your rendering loop, having a preference using values that are global
to
> your classes.
> Running your program using the option -Xincgc will smooth the garbage
> collection over time (but also reduce performance) and this can help
you
> figure out if the gc is responsible of your problem.
> -> java -Xincgc yourclass


I checked out whether GC was the problem as the first step (I mentioned
that in the initial post on this subject).  I have been running with
-Xincgc from the outset.  I also explicitly turned on -verbose:gc so I
could see when it was gc'ing, but I discovered that it gc'd rarely (I
don't create much at all during my main rendering loop) and that the
stuttering continued between gc events.

 
> You don't need to compile arrays into display lists (this is really
> useless,
> I have not noticed any percent of performance increase testing this
> feature), but it is always good to lock your vertex arrays. It allows
the
> driver to optimize the vertex data access in memory and thus gain
> performance.

Actually I got a very large speed increase when using display lists
(which is what I expected since Nvidia explicitly recommend it as being
faster than just using arrays - compiled or not)


> Make sure you don't recompile your display lists at each frame (this a
> stupid advice, but we never know...)

heh - don't worry, I'm not doing that =)


> Make sure your hard disk drive is not swapping during the rendering,
this
> would explain the poor / unregular access to the vertex data in
memory.
> If so, add more RAM to your computer.

It's not reading from disk (the terrain is generated from an fbm
fractal)


> Allocate more RAM than needed to the virtual machine, I've had the
feeling
> it was increasing a bit the performance. For this, use the flag -Xmx
> -> java -Xmx256000000 yourclass  (to allocate 256Megs of memory to the
> program)

I'll try that - I had it in mind that I wasn't using a lot of memory,
but that may be an invalid assumption.


> Make sure you don't have 3dsMax or any third party openGL application
> launched in the background when you execute your program. In some
cases,
> 3dsMAX make me loose up 70% of my application performance, and I hask
> myself
> "what the f%% is going on ?"..."oh max is running in the
background..."

Heh - no, not doing that either.


> Don't use too small arrays. Small counts of polygons like 50-200 won't
> make
> you benefit of a real performance increase. Prefer having several
thousand
> faces per array if possible.

There's no issue with the openGL performance of this code - it's a port
of C++ code which was rendering in exactly the same way and performing
fine.  Actually, it's not even that the Java version is *slow* - it
isn't - It achieves pretty much the same fps as the c++ version, it just
stutters and doesn't run smoothly.  It's like it's dropping a frame
every now and then.

 
> I'm personnaly using vertex arrays having very good and smooth
performance
> under a geForce2MX. What 3d card do you have ?
> 

Geforce 256 / Windows 2000 / 128mb ram.

Cheers,

Peter.