[Micha]

Hallo,

I have download Thomas file and tryed to render a colored glass. After some problems, I have simplified the scene - a sphere emitter and the glass in the middle. The glass (abs 0.99, abbe 200, ND1.51, RGB 180-220-136) is splitted and the liquid (abs 0, abbe 200, ND 1.33, RGB 251-242-211) is one colosed object.

Problems:
- a big black area in the bottom of the glass
- the lower glass part with liquid looks brighter than the upper part with air (seems to be an absorbtion problem)
- the foot of the glass looks so bright (to less absorbtion)
Edit:
- if I use a strong absorbtion, is it the bright wall on the side in the upper part of the glass in the second image normal?

C&C are wellcome.

[Frances]

Hi Micha,

What does it look like with absorption at 0?

[Micha]

Frances, thank you for the hint. The black areas was from the strong absorbtion.

Stay the two other problems. I think, the glass-liquid model dosn't work with absorbtion. But which one could we take? I'm waiting for Tom and Thomas.

Strange effect: at the lower samling level is pattern in the noise. I never have seen this befor 1.2.2.

[Kabe]

Problems:
- a big black area in the bottom of the glass
- the lower glass part with liquid looks brighter than the upper part with air (seems to be an absorbtion problem)
- the foot of the glass looks so bright (to less absorbtion)

The area at the bottom is a very dark green, caused by rays trapped in the glas or a couple of meters.
The bright looking parts are parts with total reflection, doesn't look wring to me.

Try reducing absorption a bit, the glass you used is quite colored...


Kabe

[Frances]

Hi Micha,

Is the "liquid" water? It looks like the color of the glass is additive. The top portion is two layers, and the bottom only one. If the liquid is water or colorless, the easy workaround would be to make the color of the liquid the same color as the glass. I guess a colored liquid would need to be a mix of the two colors?

[Thomas An.]

Stay the two other problems. I think, the glass-liquid model dosn't work with absorbtion. But which one could we take? I'm waiting for Tom and Thomas.

hmm, not sure what is a realistic absorption value (I have no real life data for that parameter). Try leaving the liquid at 0.0 and adjust the glass (maybe to 0.05 or 0.1 or... something small)

Strange effect: at the lower samling level is pattern in the noise. I never have seen this befor 1.2.2

Yeah, I have seen that pattern before (including previous betas). Does it really matter though ?

[Micha]

The area at the bottom is a very dark green, caused by rays trapped in the glas or a couple of meters.

Good, this I understand now. Thanks.

The bright looking parts are parts with total reflection, doesn't look wring to me.

I have thought, at the bottom is the glass very thick, so it must be more tinted or darker. And what is, if I look through the glass and the liquid? I have here a green Bottle with water and it looks everywhere very dark.

Try reducing absorption a bit, the glass you used is quite colored...

My image show only an example, it should be not realy a drink glass. In my original model, I try to get a green wine bottle.

[Micha]

Hi,

where are the render freaks or the NL team. Hallo, something dosn't work. Help please.

OK, here a new test with simple geometries in a white cube emitter, the liquid is a closed solid.

(1) good - single plate
(2) good - two plates
(3) good - case (2) + reflection of the white environment
(4) false - to bright, should be dark like (2)
(5) false - where is the color of the aft plate

Thomas has discover, that Maxwell remember on the previous ND, but iM~R seems to ignore the previous absorbtion factor.

So, which model could we use for colored glass with liquid inside? Should NL think about to work on some improvements?

A dielectirc material with absorbtion need two surfaces, but how do we get a liquid inside? The "split-the-glass" method dosn't work

[Thomas An.]

You should be carefull with this kind of conclusions.

1. How do you know that (3) is bright because of absorption instead of reflection? Use a high UV in your test to eliminate the reflection parameter.

2. Also, I suggest you find a real life experiment to do and compare. It is not a good idea to speculate by memory... the human mind is not always very accurate.

[Mihai]

To me it's logical the (4) is less tainted because in those areas you only have 1 surface of the green glass (the front and back sides), while in (2), you have 4.

So that's why the part where the liquid is looks lighter.

[Micha]

You should be carefull with this kind of conclusions.

1. How do you know that (3) is bright because of absorption instead of reflection? Use a high UV in your test to eliminate the reflection parameter.

2. Also, I suggest you find a real life experiment to do and compare. It is not a good idea to speculate by memory... the human mind is not always very accurate.

1. I have moved the rod complete behind the glas objects in an other rendering and it was viewable like befor at place (3), so it can be only a refraction.

2. Hmm, I will try to make a new test. My last simple test was, I have take a green wine bottle with water inside. The complete bottle looks uniform green. In my rendering I never got this solution.

Good, it seems, that you not say, the model is false, so I will try it again.

[Micha]

Hmm, every test the same. I don't like to build a better high detailed model, because it is not a subtle effect and in every image I get the same.

It could be great, if somebody could model a green glass bottle with absorbtion and water inside, so that the bottle looks uniform green.

[Mihai]

In that case just make the water a little green, increase it's absorption a bit and you will get the same shade.

[Frances]

In that case just make the water a little green, increase it's absorption a bit and you will get the same shade.

Sounds familiar.

[Micha]

Now, my Maxwell is total crazy. Here a glass block, blue tinted and abs 0.9. An air cut on the left side and a water block inside. Only in the part with the water inside the absorbtion looks right - brighter.