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[XNA] Strange framerate drop + Performance advices

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Hello guys,
After adding functionality to my project I started working on performance. That's when I noticed a problem I'm having:

Randomly, after 2 or 3 seconds or so, the framerate terribly drops (only in one frame). After it, evrth normal again. 2, 3 seconds more... & again one terrible frame! It seems like a pattern, but I cannot find a logic...

Test Scenario:
I only draw a few object (5, 10, 15, no more, really low poly cones), I stare still at the models & the problem shows. I even draw nothing & the framerate drops from 60 to 53 or so showing the same pattern.
I don't know much about PIX, but i'm able to find the problematic frames in there:
here nProf result:
any idea of what it may be?

Well, apart from that:
I noticed drawing my models reeeeally decrease the speed: What's an acceptable polycount for a model? Let's say: for a man? & a house? Is it better if I split it in many models?
Max texture size I'm using is 2048x2048. Is it ok? (the heaviest: 1mb aprox, jpg).
Biggest X file: 63mb. I should split it I guess.

So well, I hope u can give me a tip!!
Thank you for your time & help!


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I don't use XNA, but from Android dev I've experienced similar regular drops and it was due to the garbage collector. the solution was to avoid every dynamic allocation.

jpg don't matter if it comes to textures, convert your texture to 32bit tga or tif (or at least bmp) and check for the size, that's probably what it is in memory. 2k by 2k sounds quite a lot, I think most games use 512 or 1024 as upper limit.

for polycount it really depends on what you draw, if you have just one house, then probably 100k polys is ok, if you want to draw a town with 1000 of them, then 100 polys might be your limit.

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Hi Krypt0n,
thanks for answering & thanks for ur info. I didn't know 2k x 2k was so big! I've already resized most of my textures, turning them into 512 or 1024 max (except 1 or 2 that i left in 2k for quality sake).

I'm not performing any memory allocation ("new...") during the Update cycle (just instancing BoundingSpheres & struct stuff).

I'm not sure if performance improved a bit or not, but the glitch is still there...
Is it possible that the map size influences a lot? I'm using a 500x500 heightmap to generate it.

Thanks in advance,

[Edited by - Synthesizer on October 25, 2010 6:58:34 PM]

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