V-Ray Render Prepasses taking a very long time

[jessicagunraj]

I'm quite new to V-ray rendering. I've rendered a couple dozen scenes in the past few months I've been learning 3ds Max and V-Ray but this week is the first time I've encountered such long pre-pass times.

 

It has been 8 hours and I am only halfway through the third prepass. I'm using light cache and irradiance map and basically the same settings I used for most of my other renderings (all of which had relatively short prepass times - 10 minutes to 2 hours for all passes).

 

My question. Are long pre-passes normal or is this indicative of some other issue? Also, does a long pre-pass mean a short render time? {I would hate to sit through 10 hours of pre-pass only to discover that I have another 40 hours of render when I could cancel and tweak my settings.)

[Ismael]

[hrishikeshp]

Hi Jessica,

 

First of all. Your processor power is most important thing when you fire any render. second check your settings.Is your priority of high quality? or mid quality will OK for you?

 

 

 

Best Luck for Your Prepasses!!

Edited March 15, 2014 by hrishikeshp

[jessicagunraj]

Thank you for your advice. My system has the Ivy Bridge i7 processor and 16 GB RAM, so I think that processing power should be sufficient.

 

In the interest of time (I thought), I've been doing mid-quality renderings. I'm using Irradiance Map (standard pre-populated settings for medium) and Light Cache w/ 2000 subdivisions. The resolution is 2000x2000.

 

I've been watching the video that Ismael linked and I find it incredibly helpful. In truth, I hadn't realized the importance of increasing material and lighting subdivisions. I've just been rendering at the default and wondering at the weird graininess of some of my images. (I think I probably should be embarrassed at my lack of knowledge. I've read/watched dozens of tutorials recently but somehow that lesson did not stick.)

 

I let the render continue out of curiosity and the 3 prepasses finally finished after 9 1/2 hours. (I think it was actually 2 1/2 hours for building LC and 7 for the prepasses). The estimated render time was 19 hours. I'm not happy with that estimate, so I canceled the render and am taking a look at my settings again.

[Ismael]

FYI, Vlado at the Chaosgroupforum rendered the scene in the tutorial above in about 28 minutes. He used BF + LC however. The times in the video were found to be excessive and Vlado proved they were by bringing the time down so much. The principles is the good thing as you found out.

 

If you show a wire of what is it you are doing and whatever settings you are using, the more information you share the more you will be helped here.

[jessicagunraj]

I spent some time yesterday troubleshooting the scene. It seems that the HDRI map I'm using combined with the IES lights is causing a major increase in rendering times. When I removed the IES lights, the rendering times are still really long. I think the culprit may be the HDRI map. I'm using one of Peter Guthrie's skies.

 

I've attached a screen of the original settings that caused the 19 hour rendering.

[Ismael]

What is your DMC Sampler set at?

 

From your settings, nothing jump at me. Maybe try a simple VraySun and default VraySky. Have you tried an override simple gray material on everything besides the atrium glass which you could just hide? That way if your time begins to drop dramatically, your problem may be with your materials, etc.

Edited March 16, 2014 by Ismael
Add image

[jessicagunraj]

I'm sorry. I didn't include a picture of the DMC sampler because it's set to vray's default. Adaptive amount = .85 Noise thres = .01 Min samples =8 global subd. mult = 1. I tried the material override. It didn't really make any difference in render time. I will replace the sun and sky with the default and get back to you.

 

Thanks for you help.

[jessicagunraj]

I made a completely stupid mistake. Although I hid the layer I have my IES lights on, I didn't uncheck the 'hidden lights' box in render settings.

 

I was able to re-render the scene with default sky and sun in 1 hour 24 minutes and I've started another render with HDRI sky that is moving along at a more reasonable rate (though I think it's probably taking longer than it should for the sort of mediocre quality I'm getting).

 

It seems that the original 19 hour render time was caused by the photometric lights. I'll spend some time reading up and doing some small scale testing rather than using the same settings for all my future scenes. It's clear I have a lot to learn.

[Ismael]

Maybe geometry problems like coplanar faces. A quick thing, maybe download SolidRocks lite version for free and see about the time.

http://solidrocks.subburb.com/index.php?option=com_content&view=article&id=12&Itemid=31

 

If time improves perhaps it is your settings. Still too high, maybe your geometry. This is just a thought as I have never tried SolidRocks.

[Msamir]

I suppose that you're using Max's IES lights? try switching them to vrayIES they are faster in rendering.

[hrishikeshp]

Hi Jessica,

 

I appreciate your sentence "It's clear I have a lot to learn."

 

Now you will find the ways..

 

With the ref. of your all conversation, you have to think some major points when you starting any work.

1. geometry(Polygon count or spline interpolation etc),

2. Shaders (Are you using the ready made material of VRAY?) if yes, then check- Is your material's interpolation value is higher! and other factor are really need you for super quality?!!

3. Lights: How many light you are using? Keep used lights only and delete others.

4. try to keep your scene file well managed!!

5. Play with renders settings.. Offcourse LC gives you gr8 output, but think of other.

 

As a Animator / Visualizer, We should do lots of study, RnD in respected areas... The most important thing is don't follow blindly to your seniors.. Ask why every time!!!

[Ismael]

Great news Jessica, I am glad it is all falling into place.

[ankurrajput]

Hey hi,

i saw your model image , n setting,

try these settings , might help you to reduce render time.