Layered glass getting darker and darker

[Sascha Selent]

Hi everyone.

I have a general problem with layered glass. Every layer is getting darker and darker - even if I do not look through them - they are just stacked behind each other, all sharing the same material. See the image of a simple scene - some blocks with a fully refractive material and a pure white environment color, no GI, no gamma-correction or anything.

I know in finalRender there was an option to define the energy loss for each tracing, but I do not find this kind of option in VRay.

But I´m not sure if it is a tracing-problem, because in the image the block in the back is the darkest - even if two rays should be enough to trace through the surfaces to fully see the background.

Setting every cutoff possible to zero and cranking up the "Max Depths" for reflections and refractions does not solve the problem...

...well, cranking up the "Max Depths" (e.g. 200) at least does something, but it makes it more and more weird...

Anyone any suggestions?

Is it possible to let´s say trace through 100 sheets of glass without loosing energy?

I also added a simple test-scene...

Thank you and kind regards.

Sascha

[pengo]

I can't open that file maybe done in upper version than 3ds max 2011, in my opinion, (I do a lot of renders with glasses), is better to avoid the inside faces of the 3 layered boxes u always get a gradient in their borders as shown in your image and plus u'll get darker shadows from those distinct objects close each others (I'd avoid complete overlapping faces between their faces). To avoid the effect of a gradient color from their borders merge the 3 boxes in unique mesh and delete the inside faces, u'll get the correct shadows less dark respect distinct objects. Hope it can help, my english is not so good. If I'll have time I'll attach a little file

[Sascha Selent]

in my opinion, (I do a lot of renders with glasses), is better to avoid the inside faces of the 3 layered boxes

Hi pengo.

Thank you for your tips, that is a cool idea if the block stays always attached. But I don´t think this fits my needs, because the layered block itself is the plot - I have to show the assembeled block and then I have to show all the layers one by one - so I cannot delete inner faces.

I think in worst case I have to use this trick blending between opacity-mapped inner faces to make them invisible while assembled - but that is very timeconsuming and I will have a visible gap while blending...

Sascha

[Sascha Selent]

Is there no way to get this fully transparent?

Still struggeling and I do not get a good result.

Regardless of rendertimes - is there a way to get these glass-blocks looking really transparent?

I figured out that the reflections are the problem - if I turn them of the block is fully transparent without any loss of lightness. If I turn on the reflections every iteration seems to steal something from the lightness - resulting in a darker and darker look.

Please I would really appreciate if anyone has a solution for me.

I link two max-files - its the same for max 2011 and 2012 - and attach a rendering from what I get.

http://www.deepartmend.de/tl_files/e...m_max_2012.zip

http://www.deepartmend.de/tl_files/e...m_max_2011.zip


Help...

Sascha

[Morne]

yes there is something weird going on here
if I apply my own glass material to your objects, I get it in reverse
then it starts of dark, and goes lighter

even if I recreate your objects, I still get the same result

[Morne]

if you delete the big inner polys, then it works perfect

[Sascha Selent]

yes there is something weird going on here
if I apply my own glass material to your objects, I get it in reverse
then it starts of dark, and goes lighter

Yes, this happens if the max depth for reflections and reflections are too low to represent the count of the faces that have to be traced. In my example I have to trace through 7 layers which means at least a depth of 14 is needed for reflections and reflections to trace through. Setting this to the default of 5 leads to the effect you described - but now the traces can´t see through the whole block. The break-even is 8 for both - lower than this leads to darker front, higher than 7 leads to darker back...

[Sascha Selent]

if you delete the big inner polys, then it works perfect

Yeah, pengo mentioned that, but I can´t delete them, because I have to show all layers individually in an animation...

[Morne]

although, "perfect" is debatable:

[Morne]

Yeah, pengo mentioned that, but I can´t delete them, because I have to show all layers individually in an animation...

Sorry I missed that part the 1st time around...

[Morne]

ok got a fix
Instead of the planes each being a small distance from each other, rather make each one overlap the previous a bit. That seems to work

this time its perfect(ish), well its getting there

[Sascha Selent]

although, "perfect" is debatable:
[ATTACH=CONFIG]12253[/ATTACH]

Is this with deleted inner polys? Looks weird...

[Morne]

Is this with deleted inner polys? Looks weird...

yes that was

But my second test with them overlapping seems to work more or less like you want. There is still darkening to the front, but it is a whole lot less obvious than what it was

[Sascha Selent]

ok got a fix
Instead of the planes each being a small distance from each other, rather make each one overlap the previous a bit. That seems to work
[ATTACH=CONFIG]12254[/ATTACH]
this time its perfect(ish), well its getting there

Awa - thats interesting...

...didn´t try this...

I´ll check it...