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Hello there,

I'm modelling a small bathroom (modernization) interior for a customer with Sketchup.

The top of the washstand is made by a face, facing upwards with a simple white plastic material (225,225,225).
On top of it (with a distance of 0,2 mm), there is a 'solid' (i.e. a panel with a thickness of about 1 cm) with a simple glass material, made with the wizard.
The aim is to simulate a glass plate with a white coating on the bottom

The scenery is illuminated by 7 IES (downlights).

The problem is:
The glass plate seems to be to dark. It is not reflecting white, but grey. The small glass plates of the small shelf above the washstand are also too dark in my judgement.

It is not possible to increase the power of the downlights enough to lighten the glass without overexposing the scenery.

The only thing I found is this:
I can make the ceiling of the bathroom (which is white) invisible an turn on sky dome in addition to the IES downlights. But this is not the target since I wanted to show the bathroom with only the downlights turned on.

Do you have any ideas?
Thank's a lot.

Umdrehung

It is obvious. Your materials are not done correctly.

If energy of Your lights are propper and EV of camera to, then only thing that left are materials, and there You have to try.

When you say simple glass material, do you mean AGS, high grade, or low grade?

It may be that it hasn't reached a high enough SL to show properly, what SL was this?

I can only recommend double checking the scale is correct in Studio, and make sure everything is optimised.

This should help clarify what is going on: http://www.maxwellrender.com/forum/view ... 48&t=37145

Best,
Jason.

Thank you very much everybody for your help.

@ half life
Is it really a matter of caustics? As I understand the other thread I should either wait for higher SL (the sample image is 12) or give up 'correct' simulation and try to compensate the problem in another 'non-correct' way.

@JamesColeman
It is high grade glass material: Transmittance 182/182/182, Attenuation 30 cm, Nd 1,51, Force Fresnel on, Roughness 0, nothing special.
The scale is correct I'm pretty sure. SL is 12

@ zdeno
What makes me wonder is, that the glass seems to be correct with sky dome.
But if I use Emitters (IES), the glass plates remain dark grey even if I overexpose the whole scene (even the glass plates of the small shelf above the washstand).


It's the different behavior of the glass plates when using different ways of lighting (emitter vs. sky dome), that puzzles me.

Thank you for further tips,
Umdrehung

Give AGS a try instead of using high grade glass. You're only going to see reflections in the glass anyway, no refraction or caustics.
And maybe try rendering just that section to a higher SL, maybe 16-18 to see if it clears. Then you could composite the section into the final picture.

umdrehung wrote:the sample image is 12

sl12 is really quite low for an interior image with this setup

numerobis wrote:

umdrehung wrote:the sample image is 12

sl12 is really quite low for an interior image with this setup

This is true, but you may also want to keep the ceiling in place and use a Z cut plane to render your scene. This way, the white of the ceiling will be reflected and contribute to the scene in a correct way. As it is, you can see black reflections in all shiny things in your scene because there is endless blackness above.

Edit: You can also use some cleverly placed "fill" lights too.

umdrehung wrote: The top of the washstand is made by a face, facing upwards with a simple white plastic material (225,225,225).
On top of it (with a distance of 0,2 mm), there is a 'solid' (i.e. a panel with a thickness of about 1 cm) with a simple glass material, made with the wizard.

I didn't catch that at first reading (poor english) sorry. But Half Life's answer lighten me up. how You build Your scene. This glass box over solid white face is very hard to compute and it have to be faked to get reasonable rendering time (not 35 SL ).

Fastest way is to turn off glass box for GI computing.

umdrehung wrote: What makes me wonder is, that the glass seems to be correct with sky dome.
But if I use Emitters (IES), the glass plates remain dark grey even if I overexpose the whole scene (even the glass plates of the small shelf above the washstand).

It's the different behavior of the glass plates when using different ways of lighting (emitter vs. sky dome), that puzzles me.

Looks like with skydom You have uniform DIRECT light from every possible point of view in opposition to focused IES lights and plenty of Indirect week lighting.
So looks like with skydom there is always some direct ray that rip through glass and back to camera in good condition.

Bubbaloo wrote: You can also use some cleverly placed "fill" lights too.

BB don't be so cruel . in so small batchroom with 7 IES there are not to many place to put additional emiter

Thank you all again.

@zdeno

Fastest way is to turn off glass box for GI computing.

I simply tried to model the plate the same way it was built in real world: transparent float glass with a white coating on the bottom.
If I turn it off how can I get the desired result?

@Bubbaloo
First I thought it is a problem of the missing ceiling too. But the result with the ceiling turned (z-clipping or turned on 'invisible) is pretty much the same and the render time increases enormously.
I think it is because it becomes a real 'closed' interior.

@JamesColeman
I think you are right and I should give AGS a try. I didn't do it by now because in similar scenes the glass looked kind of 'flat' with AGS but in this case the perspective is a little bit different (more distance to the glass plates).

@numerobis
Maybe I am to impatient, but I always keep an eye an the preview window. Until now I thought the preview image gives a good prediction of the later result even if the first SLs are to dark or 'misleading' in another way.

Umdrehung

umdrehung wrote:I simply tried to model the plate the same way it was built in real world: transparent float glass with a white coating on the bottom.
If I turn it off how can I get the desired result?

because glass would still look cool because of reflections refractions, but wouldn,t block light and under solid panel would get proper lighting faster than in 35 SL.

how glass ( 0 roughness) looks it all depends on refraction/reflection. There are no diffuse factor then so turn off glass for GI didn't have influence in glass look itself but have great impact on surraunding objects.

active glass ( in this example) for GI only produce caustics and doing big mess stoping direct light creating big shadow which have to be lighten by indirect caustic at 35 SL ( 24 days later).

but I can be terribly wrong too. mayby just try with small region render to help us all

@zdeno
Thank you very much - that's it - you got it.

I turned of GI for the glass and boom: the rendering looks like it should (of course still a very low SL of 11)



I suggest that the glass no longer drops a shadow on the white plate underneath.
What still isn't' completely clear to me is that sky dome has the same effect. But that's not important. Further on I will complete my work with GI turned off for the glass plate.

Thank you all
Umdrehung

great, I am glad I could help