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Optimizing render times with Skylighting

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goofibulatorOptimizing render times with Skylighting
by on May 22, 2006 at 10:05:50 pm

All,

Forgive the noob-ness of the question coming up. I know just enough about Max (v6) to be dangerous, and am looking for some help with regards to optimizing a scene so it won't take days to render.

I'm aiming for as photorealistic as possible with the scene. It's a sparse room with some boxes (a la somebody getting ready to move) and I have put a skylight into the scene for lighting, mostly because it gives really nice environmental shadows. Here's a link to what I've got thus far...

http://www.flowmedialab.com/clients/misc/room_skylight.jpg

The trouble is, that one frame took half an hour to render, and I've got to pump out 30 seconds worth. I have a very modest three machine render farm, one current box and the other two are a couple of years old, so I'd like to make things render a tad quicker than 7 days as the deadline looms.

With regards to Skylight, I know that I can lower the 'rays per sample' to get quicker renders at the expense of 'noisier' images. Right now I'm at 20, and much less than that and it's getting too noisy. I have tried playing around with other lights (area spot, target spot, omni's) but I can't seem to figure out how to get those nice, soft environmental shadows going on. I confess that my knowledge of ray tracing (and, one could certainly argue, 3d in general) is abysmal, as I tend towards the 'flying boxes for motion graphics work' school of 3d.

And so my question: how can I get the same look (or better or at least close) as the above link and keep the render times in check (say a couple of days or so, preferably less)? Can I use skylight more efficiently or should I be looking at other lighting options?

Any and all suggestions are welcome, and thanks in advance,

alan


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Steve WhiteleyRe: Optimizing render times with Skylighting
by on May 25, 2006 at 11:52:31 am

Hi Alan,

A solution we sometimes use is to create a light ball (we call it Fakiosity....arf) Basically a ball of omni lights - imagine a sphere around your whole scene with an omni on each vertex. Make sure they are instances of eachother. Use a low value for the light and make it cast shadow maps....increase the map size (dependant on your scene scale), check absolute bias and increase sample range to something like 15 to 30 (softens the shadows). So you have a load of duplicate omnis casting shadows all round the scene. This gives a similar effect to skylight and can be much faster to render.

Your scene looks fairly simple and shouldn't really be that slow on a skylight render. Maybe you could post it, or a stripped down version, so we could check the settings.....or is there a big raytraced waterfall behind the camera?!!



Steve whiteley
Animation Director
Gizmo Animation Limited

http://www.gizmoanimation.co.uk


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goofibulatorRe: Optimizing render times with Skylighting
by on May 25, 2006 at 6:33:47 pm

Steve,

That is so cool! I'm getting results roughly equivalent to the approach I've started using based on suggestions in another forum: using sky with Light Tracer. This certainly sped things up by roughly a factor of 10 (with some issues with regards to some materials) but I'm certainly going to look at fakiosity (nice name, btw) as that speeds it up by another factor of 10. Yes, I'm sure I have a setting somewhere that's draggin the whole thing along... as I say, I'm a bit of a hack at the 'photorealistic' side of things.

Thanks again: this may be just the solution.

Now if I can just figure out Array to make a perfect sphere of omni's...

-a


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Steve WhiteleyRe: Optimizing render times with Skylighting
by on May 26, 2006 at 11:30:16 am

an easy way is to make a circle shape in the top view, create an omni light.....click: tools/spacing tool (top menu) and pick the circle as the path (make sure you're making instances). Once you have a ring of omnis, select them all and shift + rotate them about the middle in the front view by say 30 degs, in the clone dialogue that pops up make 5 instances (you should now have a hemisphere of lights. Then just select them all minus the bottom ring of the hemisphere and shift + rotate them to make a ball.

Steve whiteley
Animation Director
Gizmo Animation Limited

http://www.gizmoanimation.co.uk


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goofibulatorRe: Optimizing render times with Skylighting
by on May 26, 2006 at 2:17:51 pm

And an even easier way is to just run this script...

http://home.wanadoo.nl/r.j.o/skyraider/e-light.htm

Works like a charm in Max v6!

-a


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Steve WhiteleyRe: Optimizing render times with Skylighting
by on May 27, 2006 at 6:34:03 pm

Hey Alan that's pretty cool....ta! Shame it doesn't create instances but good none the less. Hope your render times are now more manageable.

Steve whiteley
Animation Director
Gizmo Animation Limited

http://www.gizmoanimation.co.uk


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