Light shining through frosted glas/plastic

[danson]

Hello everyone,

I'm new to this forum - but not that new to Keyshot.
And I'm very happy that I found this forum, where so many users
share their knowledge about keyshot. In the past days I read many
posts about the problems I have, here in this forum. But I couldn't
find a way to solve them.

Currently I face two major problems with my scene I'm working on.
I have a few LEDs coming out of a pocket lamp. They are covered
by a lightly frosted glas.

I want to render this scene mainly with the light from this LEDs.
The ambient light is set very dark. The lamp is hanging in the air shining
to the ground.

If I set the glas to frosted, you can see, that the glas is lighted from its backside.
But there won't be any light seen on the ground.
Only if the material is not frosted there will be light projected to the ground.
How can I fix this? It should be a frosted glass.

The second problem I have is about all mattfinished surfaces. I have many white
pixels in the rendering. In the past days I read many posts about this, here in
this forum. But trying to apply this to my scene didn't work. And I can't spot the
problem - just thinking it has to do with the rough surfaces I have in the scene.
Can anyone tell me the main reason to this problem or any how-to-set tips
for the materials.

Thanx a lot
danson

[andy.engelkemier]

You'd be breaking most of the major "rules" for this type of rendering software with your scene, but I can think of one thing you might be able to do.
Cheat.
Have one light that lights your frosted glass. You'll want this value low enough that it gives no real light contribution to the scene, or you'll get fireflies (white spots). Have a second spot light in front of that in the shape you want it, hidden from reflections and camera. The goal of this light is to Only project light into the scene.

Always avoid light going through objects if you can, especially closer to the light source. The only Real way to do that is with caustics, and if you've played with that you'll probably have noticed that your render time skyrockets. And the further particles have to travel after being dispersed, the worse that gets. The same goes for GI really, which is why your frosted glass creates a bunch of fireflies.

So there it is. Cheat, whenever possible.

hope that helps.

[danson]

Hey Andy,

thank you for joining in this discussion.

I tried cheating by using Photoshop before. But that wasn't the way I wanted to succeed.
And the results were not what I expected.
To cheat within Keyshot sounds to be a better way of cheating and it seems to have potential.

I will check this in the next couple of days and maybe post a screenshot.

Thanks again for answering.

danson