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Kerkythea Rendering System • View topic - How to avoid dark areas of overlapped glass?
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How to avoid dark areas of overlapped glass?

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<<

pjfry

Posts: 2

Joined: Thu Aug 25, 2011 2:18 pm

Post Thu Aug 25, 2011 4:47 pm

How to avoid dark areas of overlapped glass?

Hi Guys,

I use Kerkythea to render some simple models which I need for presenting the structures used in my research. I find glass very useful (Kerkythea too!) as it is transparent and therefore allows me to show internal parts of complex structures. My problem is that areas in which glass objects overlap become very dark (gray). I attached a simple example which illustrates the problem. The upper part of the image shows few yellow objects (yellow dielectric glass) which are very dark in some areas (encircled). Adding more glass objects (bottom part of the image) just makes everything worse by introducing additional "gray snow" areas (also encircled). Now you can imagine how a complex glass structure will look like - so dark that it would be impossible to distinguish individual objects.

I suppose this is a normal appearance of the dielectric glass (I am like a beginner), but is there any way to obtain a crystal-clear images with overlapping glass objects (i.e., without too much darkening)? That is, how to preserve transparency and glass-like appearance without darkening? Is this a problem with the parameters of the glass or sun? I tried to play with both to no avail.

I also attached the kzx file. I would appreciate it very much if someone can correct the file and show me how to obtain a crystal-clear image (if this is possible at all).

Thanks!

Fry
Attachments
test.kzx
Kerkythea file
(4.14 KiB) Downloaded 221 times
test.jpg
Example
<<

Sergio

KT-Explorer

Posts: 224

Joined: Tue Jun 24, 2008 10:22 am

Location: United Kingdom

Post Mon Aug 29, 2011 6:33 pm

Re: How to avoid dark areas of overlapped glass?

Have you tried the thin glass material instead?
<<

Fletch

KT-Team
KT-Team

Posts: 8564

Joined: Fri Oct 27, 2006 2:38 am

Location: Milwaukee, WI USA

Post Tue Aug 30, 2011 10:08 am

Re: How to avoid dark areas of overlapped glass?



<<

pjfry

Posts: 2

Joined: Thu Aug 25, 2011 2:18 pm

Post Tue Aug 30, 2011 5:23 pm

Re: How to avoid dark areas of overlapped glass?

Thanks, Guys!

I realize now that I am more than a beginner. I have not had any clue about the options you mentioned. I also wrongly thought that absolute physical dimensions are not important as long as the aspect ratio of the objects is preserved.

You are right, thin glass works! Also, increasing the number of Max Scatter/Dirac Bounces from the default value of 5 also works with dielectric glass. I also tried to select setting "20. Metropolis Light Transport (BPT)" and it seems that this would work too (I say "it seems" because it takes forever to render the scene - it goes through 10000 iterations; I stopped after 10).

Thank you again!
<<

Sergio

KT-Explorer

Posts: 224

Joined: Tue Jun 24, 2008 10:22 am

Location: United Kingdom

Post Tue Aug 30, 2011 7:26 pm

Re: How to avoid dark areas of overlapped glass?

You can stop your render whenever you feel you have a clear enough image with any unbiased method. Normally and depending on your lighting conditions it will take around 150 or 200 passes to get an acceptable image. The darker your scene the longer it will take to render.

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