render time and lights

[Ron Eddy]

I've just started using nXt in the last month, but have used Accurender since 2004.

I'm trying to get a handle on render time and the use of lights.

The attached image is a reasonable example of both.

1) This image is set for 3072X2304 pixels. 28 passes took 24 hours and 12 minutes. This is a little higher res than we usually use for web presentation but the same question applies: what can I do to reduce render time?

2) There's something about the math for lights turning on that I'm missing. The light in the service counter under the "u" in "cmu" failed to turn on. it's a duplicate of all the ones on either side of it, which DID turn on. With 140 lights in the image, I figured by pass 18 they should all be on if I'm running at 8 lights per pass.

Thanks,
Ron

[akinlolu olugboji]

As a thumb rule always render small resolution which are always faster first. When all your settings are to your satisfaction, then go big time.

[Ron Eddy]

Thanks. That's what I've been doing generally. I honestly can't remember whether this light came on in the lo-res version or i just figured it would. i'll watch more carefully.

[Peter Milner]

For web presentation you should be rendering at 1024 x 768. This will speed things up a lot.
Blurry reflections and blurry transparency are 2 of the biggest factors that can slow a render.
Use glossy materials instead where you can, particularly for small details.
With 140 lights you'll need several hundred passes for some of the reflections to start resolving.
Turn off any feature lights that can't be seen in the render view unless they're contributing significantly to the overall ambient light.

[Roy Hirshkowitz]

Nice image. All of Peter's suggestions are very good ones.

The time will vary approx. linearly with the number of pixels-- so a 6 megapixel rendering like yours will take 6 times as long as a 1 megapixel image which is usually more than adequate for web-based work.

I suspect the light in the service counter is working fine-- it's just sampled a different point on the light will fill in after more passes. (Just guessing here)

Another way to save some time is to render without the plants in the background. You can render a background separately and alpha composite things in.

The Path Tracer may also be a good choice here-- in that case I'd leave the plants in. If you want to share I can try this model out here-- use the Upload a File item under Support if you're so inclined.

[Ros. Riha]

I know it is not directly related, but - it does not seem you use pathtracer engine, which should be better for this application ... passes took less time, but you need more of them... in fact it speeds up the whole process, because you get to know mistakes in your setup earlier...