blotches in rendering clear material

[ERANB]

Hi all,
I'm trying to render a box with clear door. the door is supposed to be from clear plastic but every clear material except glass renders poorly.
Glass and solid glass renders fine but don't look as plastic.
I played with all the settings: ray bounces, caustics, interior mode/product.
Is it related to the environment?
the weird part is that in real-time view it looks great/
Attached are a few sampled renders.
any advice will be much appreciated.

Thanks
E

[DMerz III]

  found out recently that the realtime view handles caustics much better than the render output. Not sure the reason, but hopefully it gets resolved.

Here's my recommendation based on what little I can see from your scene.

In the meantime, I would not use the jewelry settings for this render as it will inflate some settings which will only slow down your samples per second. If you absolutely want caustics on, I would use interior mode it usually helps clean up the caustics. Though, unless you're specifically needing caustic flares, probably would avoid using it altogether. Without seeing the rest of your scene you could probably get away with 6 to 8 ray bounces, and you could use anywhere from 3-5 global illumination bounces (this setting really affects render times).

Shadow quality also affects how long you'll be waiting. I would start at 1 and if you are not getting the results you're looking for, go up to 3.

You mentioned the environment, that is definitely a possibility; Physical lights will help brighten up areas that you feel might not get enough light from an HDR environment, but will also take a 'little' more calculation time in the render. If your scene is incredibly dim though, you are going to want to brighten things up as low-light can actually lead to more noise in the end especially in shadowy areas.

[ERANB]

thanks you very much for your  insights. I'll try your way and report back

[ERANB]

tried everything. still no luck. the outcome is not usable. it's so frustrating! the dead line is today. the PC render the whole night. I'm hopeless.
is there a diffrenece between the global illumination in the "lighting" tab versus the "option" in render window?

[RRIS]

Would it help to add some objects to gently illuminate the inside? For example, a large plane in each cavity? Just enough to lighten the shadows so that you don't have to rely on only indirect lights.
You can hide the object lights from camera and just have them illuminate.
Just a wild idea, could be rubbish.

[mattjgerard]

Would it help to add some objects to gently illuminate the inside? For example, a large plane in each cavity? Just enough to lighten the shadows so that you don't have to rely on only indirect lights.
You can hide the object lights from camera and just have them illuminate.
Just a wild idea, could be rubbish.

Not rubbish at all, I do this all the time. Works great. I never use interior mode so I rarely get those splotches. Letting the image bake for a longer time usually resolves those for me.

My other suggestion would be to look into using a one time render farm service to speed up the return if your deadline is fast approaching. But you need to get the scene sorted out first!

[ERANB]

thank you all for your advises.
I ended up rendering the solid body apart from the transparent part and merged them in Photoshop which is a lame way to solve it but in the time frame I had..
I got the suggestion of a light source inside also from a coworker. tried a small source and did not see any improvement. will try again and report.
I'm deeply disappointed in Keyshot performance in that regard. I remembered transparent material were more difficult, but did not expect that.

[TGS808]

Glass and solid glass renders fine

You should have gone with that and saved yourself the hassle. Problem solved.

but don't look as plastic.

For a clear, transparent material, any difference between the two had to be negligible.