light dappling effect on surface of object inside clear plastic container

[wolf]

Hi, I have had this problem for many years now with Keyshot and I am finally looking for a solution.
I am trying to render a scene that shows a product inside a transparent plastic container on Jewelry mode but even though I upped the samples to 480 it does nothing to stop the dappling effect of light on the surface of the blue object inside. I even rendered a smaller patch at double the resolution set at 520 samples to see if it made any difference and it didn't.
I have attached a render of this effect and attached a screengrab of the live view where the dappling is hardly noticeable.
Please can someone explain what is happening here and how to get rid of it?

many thanks

Rob
Windows 10
KeyShot 7.2.135
Solidworks modelling system 2015
Steps to take to reproduce the problem: Increased samples to 480

[DriesV]

Hi Rob,

This is a side effect of rendering caustics, which is enabled for the Jewelry Lighting Preset.
The Jewelry preset also uses Interior Mode, which requires caustics to be enabled in order for objects to be illuminated behind transparent materials.
You could try using Product Mode instead. The internal objects should be illuminated, even when disabling caustics. However, you may see more overall noise initially, compared to Interior Mode.

Dries

[DriesV]

As for why you get splotches in offline rendering, but not in real-time, then that happens because caustics are handled a bit differently in offline rendering.

Dries

[wolf]

I really appreciate your response DriesV but when I'm rendering a whole shelf display the overall scene is so much more photoreaslistic in interior or jewelry mode because of the lighting computation which is of course why they take longer to render.
You right of course that in product mode the artifacts are not there but it's a shame that keyshot can't fix the problem. I wonder if a keyshot engineer has a response to this.

[KeyShot]

Computing caustics (such as those underneath the plastic) does require a decent number of samples. If you would like us to investigate if the model can benefit from further optimizations then it would be great if you could share it with us at info@luxion.com. One possible option for you is to simplify the transparent material to window glass. This will also result in a simplified caustics computation and therefore a much faster rendering.

[wolf]

Hi Keyshot, yes please! I'll send the file to info@luxion... 
Many Thanks