Macro shot with shallow DOF - Advanced render controls

[GWMN]

Hi all,

I'm a newbie to Keyshot but loving the results I'm getting and the workflow in general.

I'm attempting to render an 11k x 7k macro shot with shallow DOF and translucent materials (leaves).  When using Max Time the DOF stays noisy even after 10-15 hours of rendering.  This led me to try Advanced Controls but renders are taking way too long (15 hours to render 15%).

The most recent settings I've tried are...

Samples 8 - I've a feeling I should bump this back up to 16.
Ray Bounces 10 - Take this back down to 6?
Anti Aliasing 1
Shadow 2 - How much doe this value affect render time?
Global Illumination 1
Pixel Blur 1.5
DOF 2 - How much does this value affect render time?  If I bump this up to 3 or 5 is it likely to improve the noisy DOF?
Sharp Shadows checked.
Global Illumination Cache checked.

Any advice or help appreciated.

P.



I'm also saving/working to a USB3 external hard drive.  Could that affect render time?

[TpwUK]

Ouch! 15 hours is a long time. Your settings there are ok but the samples do need to be higher. DOF quality will play a massive part in slowing things down as does translucency.

A few things to clear up here though ... Why the need for an 11k x 7k image ? That's huge, like billboard size ! Producing images of this size requires lots of RAM where a single tiff image may require as much as 10 G-bytes, so you could also be running out of memory and using swap space, which would be dramatically slower.

You say you're saving to an external device - Are you on a laptop ? If so then unless it's a really high end one you are likely to find that your processor is too slow and have two few cores/threads to be able to deliver what you want in the time scale you are expecting. 

Martin

[GWMN]

Hi Martin,
Thanks for the quick reply.
The 11x7k render is so the image can be used for print purposes as well as online - Point of sale being the largest format.  The problem is the client needs lots of extra image area for different formats.  All of the interesting stuff is happening in an area that's approximately 6 or 7k square.  The image outside of this is made up of an out of focus backplate that I rendered in Keyshot and re-imported (a very quick render). 

I'm using a Mac Pro with 64GB of RAM and using all 16 cores of the CPU.  The external hard drive is just laziness on my part really as I'm working between 2 machines (home & work).  Saves on copying files across each time I move (I know, pretty bad hey).

I'm doing a 3.5k test render at the moment with Advanced Controls on default other than DOF bumped up to 3.  It's at 5% after 1 hour.  The render seems to slow down at the same point each time - just as the DOF really begins.  Still looking noisy with the DOF at 3.  I'll bump up to 5 and see how that goes.

Paul.

[TpwUK]

Try doing a region render with whatever settings you choose and let it render to completion - If you make the region 10% of the total image size and place it where you need good detail you should get an approximate render time. You can then tweak your settings to get an acceptable result.

Martin

[GWMN]

Good advice, I'll try that.  Thanks again.