Glas and Light behaviour

[waaazoo]

Hello everybody,

I'm working on a complex project with a lot of lights, glass, mirrors. So far, so good, but I stumble over some problems with light affecting glass objects.

Today, I have two big problems:

- I would like to simulate edge lit glass. I tried a lot of things, but I cannot find any solution which is looking real. Can anyone give a hint how to achieve that ? (I'm trying to do that on a spiral stairway)

- would like to simulate the Harcourt Marie Louise lamp from Baccarat. But I cannot get any light effect into the glass (please see attachement for reference). I tried with a blend material to add some light, but it looks really fake. What can I do?

any help would be really appreciated.

cheers

[waaazoo]

https://www.youtube.com/watch?v=4kuaH3EHeSg

we should be able to simulate something like that, no?

[Morbid Angel]

Its a touch challenge. In your reference if you look at the glass it self, since it does not have much gloss in the refraction, mostly entire color comes from the LED illuminating the environment it self and that refracting back into the glass. Generally speaking to get realistic glass in vray you really need to crank the reflection and refraction depths in the shader to something like 30/30 or 50/50. You also have to build out the glass and LED objects as physically accurate as possible, meaning as if they were build in the real life. The closer you will get them to reality the better it will look.

[Morbid Angel]

I've done a quick setup, here is what I was talking about.

[waaazoo]

Thanks Dmitry,

A glass with edge lighting has typically, as shown in the video I posted, an LED ramp light on one edge (with an enclosure), and frosted glass on the edges, so the light illuminates this frosted glass. As you can see in the video, you can even create artwork or patterns on the glass by frosting this motiv, which is capturing the light.
I'm not sure the light "travels" as it should in Vray, making such simulation possible.
In your test, you have a edge light at the bottom and on the top, right?

this is a test I made yesterday (one of them). I tried, for the glass:
- to use only clear glass
- clear glass top and bottom, frosted glass on edges (I think this is not good as Vray has problems computing the refraction, is it?).
- frosted glass everywhere
- two objects, step itself with slightly frosted glass, and edge object with heavy frosted glass. (this is what you see in the rendering)

overall, I'm using 20 reflection/refraction depth, but I will try to increase.

Concerning the Lamp (the other problem), I will also make a setup corresponding to the reference photo.

cheers

[waaazoo]

I made a bunch of tests. Each Glass step is 3cm thick. Quite interesting results.
Using two materials is obviously wrong.
The simulated 3 sheets of glass is just by adding edge loops on the edge faces to give the impression to have several sheets. It looks ok to me and is much faster (obviously) than having 3 real sheets.
I limited here the depth to 20, but I make a test to see if it makes any visible change to have a depth of 50.

what do you think?

[vlado]

Actually the light in the glass comes from internal reflections. You will need to turn on the "reflect on back side" option in the V-Ray material and increase the number of reflection and refraction bounces. You might also have to set the cutoff to 0.0

Best regards,
Vlado

[waaazoo]

Thanks Vlado,

"reflect on back side" is already ON. Here is a new set of tests where I increased the depth to 50. In fact, I find that it looks better with depth 20 only. I will test with the cutoff at 0.0 to see if it makes any changes.
I'm also doing a set to compare with more reflection and refraction subdis, to see if that makes any noticeable change (apart from noise reduction)

[waaazoo]

[Morbid Angel]

waaazoo can you post your sample scene here?

[waaazoo]

light_test_step_chaos.zip

Hi,

Here it is.
There are some group of stairs, which correspond to the latest pictures I just posted.

Cheers,

Olivier

[waaazoo]

Here is also a test to compare a glass with refraction glossiness and glass with just a very fine bump.

[waaazoo]

Another Test. This time I played around with a bumped glass (no refraction glossiness). It's bumped only on the sides and underface. In addition, I mapped the Refraction color amount on these same faces.
Last picture (bottom right) is a blend Material mapped to switch between glass and a nearly white material. I hope it's understandable.

[waaazoo]

Vlado,
What would be the correct way to do sandblasted glass? I mean glass, where some parts are sandblasted. So far, I understood that it's wrong to put two different materials when there is refraction, because Vray would have problems to compute the correct refraction behaviour.
Before, when I wanted to simulate a sandblasted logo on a glass, I just used a blend material with glass as base material and a almost white Vray Lambertian mat masked out with a texture.
If we look at this example (above) with the blue lit stairway (reference photo), it seems obvious that the edges of the glass sheets are sandblasted (or acid etched).

In my last test round I simulated the sandblasting on the edges by a slight bump and variation on the refraction color amount. This gives at least the freedom to use just one material with some areas sandblasted and some not...

What is the right way to do?

cheers,

Oliver

[Morbid Angel]

you can use switch material and plug your mask texture into switch, in that case the refraction works perfectly.