Difficulty with colored, semi-transparent plastic or glass

Would anyone have any good design techniques to get a really rich colour from a semi-transparent glass or plastic? I'm looking for an effect similar to the popular gel or Aqua styles. I've made many attempts at reproducing this, but I can't seem to even get close.

Granted, this is probably a very difficult effect to achieve, but has someone out must have some tips to share.

My reference image is: http://www.flickr.com/photos/powerhouse_museum_photography/19748714...

Attached is my best attempt, and even then, this is only after mucking around in the nxt editor and cranking up the saturation to max.

Attachments:

die.jpg, 55 KB

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Permalink Reply by Render Plus on December 1, 2010 at 12:58pm

Here is the reference image:
(I used the camera icon at the top of the reply area to add an image)

Here is your image:
(You might upload your .skp file as well in case anyone has time to play with it)

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Permalink Reply by Craig SImons on December 1, 2010 at 3:13pm

Attached in a zip.

Attachments:

dice.zip, 311 KB

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Permalink Reply by Render Plus on December 1, 2010 at 3:44pm

I haven't looked at your model yet.

A couple of hints off the top of my head:

1. Make the material on the faces of the dice more transparent, and give it a higher index of refraction (1.3 or higher). This will provide good distortion through the dice.

2. Make sure the material is marked as "thick". This will treat the dice as "solid"

3. Turn on caustics for the material as well. (This provides more interesting shadows - especially from a point light or spot light)

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Permalink Reply by Richcat on December 5, 2010 at 4:48pm

Hi Craig

Had a go at geting some where near the image you posted.

One thing turn off "Move transparent colors towards white", which in the IRender support dialogue.

The scene is lit by your lights but moved spot and used the studio hdri for the sky. Added more transparancy and increase reflection and refraction values, and took out the glow to the spots, but It may be an idea to put back to get bottom spots to show "white", but may be only to these.

I have attached skp, so you can see settings, and play further.

Used brightness slider to lighten.

Al - Tried with path trace but would not render until Turn off lights

Hope that helps - Richcat

NB. You may need to reset "batch rendering settings", by opening it and just clicking " batch rendering setings" and clicking Ok as i did with your skp.
Packet

Path Trace

Attachments:

dicepr.zip, 226 KB

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Permalink Reply by Render Plus on December 6, 2010 at 7:28am

Rich,

Was the version you uploaded the one which did work with Path Tracer, or the one which did not.

I moved the light closer to the die and rendered it with path tracer. This is what I got after 5,000 passes. (about 8 hours)

I am making another one with a much smaller light bulb (0.05" instead of 3" to see what effect that has. (The smaller bulb makes the light come from almost a single point, rather than a large, (compared to the size of the die), area.

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Permalink Reply by Richcat on December 6, 2010 at 9:14am

Hi Al
Yes - just turned on artifical lighting and changed to path tracer, and before it renders get error message below.
I think there were some recent rare issues with caustics and path trace with accurender looking at latest bug fixes listed here.

I would have thought the caustics would have resolved themselves after 5000 passes, could this also be an issue? also noted Roy has just updated nxtimage editor.

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Permalink Reply by Craig SImons on December 6, 2010 at 12:04pm

Al and Rich,

Thanks for taking the time to look at my problem. I've rendered using the file Rich provided and found the results much closer to what I was expecting. I've only been using irender for a couple of months and still have a ways to go in discovering what each setting does.

That being said, I've noticed that the support dialogue has many options that seem to have a huge effect on the output. In this particular case "Adjust transparency to make more transparent" and "Move transparent colors towards white". Is there are reason as to why they are hidden away rather than under the Render or Lights section? I don't really think the support dialogue is documented anywhere either. I would love to read up on them for future knowledge.

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Permalink Reply by Richcat on December 6, 2010 at 12:16pm

I believe its something to do with the lookof sketch materials when they are translate carried across to Irender and vice versa

Theres a wiki page here on the particular info, check the rest of the site there lots of info and links

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Permalink Reply by Render Plus on December 6, 2010 at 1:08pm

The fuzziness may have been related to processing sky through the cube.

Here are later results - using lighting channels to isolate the sky, the 3" light beam, or a 0.05" light beam which have better results. I set the sky lighting channel intensity to 0.01 to really reduce teh light from the sky.