Unacceptable render times.... why???

Common Common :: Render Theory
1

I’m posting on behalf of Mike Munson (cdi). He hasn’t gotten his login here validated yet and needs help quick. He’s no newbie to vray, but has been having trouble with 1.46.

With a lot of experimenting and help from this site, we’ve come up with some decent settings, and are starting to understand the process from Vlado’s tutorial.

Mike has a scene he’s working on that’s taking way too long to render. He’s gotten the time fairly reasonable when rendering up to 1100x1700, but when trying to render a final at 2400x3600 his render times are insane (around 15 hours). He has played with every conceivable setting, but no joy. He’s hoping someone will be willing to take a look and figure out the problem.

I’ve posted a screen shot of his settings, the best render he’s gotten, and a basic version of his scene to my ftp. (Login info here: http://www.customcadsolutions.com/ftp.htm )

Just log in anonymously and get the files in the ‘public/cdi’ folder.

Thanks!

2

UPDATE:

Mike has been doing some further testing, and thinks it may be related to IES lights. He has something like 10 instanced IES lights in the scene.

#1- Could that be the cause?
2 - If so, is there a way to simulate this? (with area lights maybe?)

Thanks

3

IES lights are known for being noticeably slower then a standard lights.

4

Depends on the distribution you need… but a gradient
placed in the “projection” slot of the light usually gives quite good results.

cheers

5

Ive noticed with IES lights that by reducing their brightness value, even though not physically correct, they tend to render faster for some reason. I generally supplement this with vray sphere lights in the middle of rooms under the light fittings

One setting i couldnt find in your settings is the QMC noise value. I find this can be raised from the defaults (from 0.005 to 0.01 maybee) which isnt that noticable unless you have lots of aluminium and blurries. makes a big speed difference. use .13 for more of a speed improvement.

personally i would try rendering with the secondary ray bias at about 0.001, reduce max transparent levels further and use adaptive QMC.

i havnt looked at your images yet so maybee none of this is relavant

6

this all comes back to the whole “bright scenes render slow” problem. ive done extencive tests in recreating IES lights. sure you can fake it with a gradient ramp made to look like the IES light pattern. ive very succesfully created a gradient ramp for that lovely IES everyone overkilled hehe. however. it lacked the brightness that the ies light had. so i started playing with the falloff distance and light multiplier and unfortunately render times shot up. so i backed off the multiplier and then started using output maps in the gradient ramp. this also shot the render time up. In another post somewhere in here you will see something about HDRI projector lights that i did where i pointed the ies light at the floor. then placed a normal light in the exact location and changed viewport to look from the light possition. and turned off the spot light then rendered the ies light patter n the ground saving it as an HDRI. this i used in the projector map slot. i had more luck with this that with the gradient ramp. but yet again when ever i try to bring the result close to the ies the render times start shooting up.

7

It sounds to me that you haven’t adjusted the irradiance settings after setting the resolution higher. Example:

if you render with -3 -1 @ 800 x 600, you should render with -4 -2 @ 1600 x 1200.