Author Topic: Translucent plastic silicone tubing material, what is a good approach?  (Read 3238 times)

2020-09-04, 21:56:46

SharpEars

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I am referring to the type of silicone tubing showin in the attached pictures (soft milky tubing and other soft white or off-white shapes made out of milky translucent silicone).

Here is a good video showing it in use, which is helpful to see its translucent/transparent characteristics when fitted on to objects (especially starting at around 1:15 into the video): https://www.youtube.com/watch?v=Jq55YGcunrg

I am not sure if this is a good case for SSS, or if it requires full transparency and a Volume material. If anyone has created anything like this and/or knows giw a material that has these characteristics can be created, I'd appreciate the details.
« Last Edit: 2020-09-04, 22:08:44 by SharpEars »

2020-09-05, 01:08:41
Reply #1

burnin

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2020-09-06, 18:34:09
Reply #2

SharpEars

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Tried what was suggested there. Yes it looks like translucent hard white plastic, but I was looking for something that looks like translucent milky silicone (i.e., soft looking, but not sure what material characteristics are needed to give this impression).

It is the difference between the below two pics (hard plastic on the top (first example), soft silicone tubing below it

The bottom silicone example is in a light blue color to help separate color from other optical features of the material. It clearly shows that color saturation plays some sort of role in making it look "soft and silicony" and not like hard translucent plastic.

Compare this with the closest (in color and translucency hard plastic item I could find at the ) second from bottom sample.

Also a rolled silicone sheet is at the very bottom for a good reference of depth, layering, shadows, and highlights. Plus, something about it makes it look unmistakingly soft, and it's not just its geometry (i.e., the fact that it is rolled up and imperfect). I think it's how the saturation of the material works into the translucency, but trying to simulate that with the Scattering Directionality and Color of a Volume material I have found nearly impossible.




« Last Edit: 2020-09-06, 18:51:22 by SharpEars »

2020-09-06, 19:14:18
Reply #3

SharpEars

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My best attempt so far is attached (4k/very long render time with caustics on - noise level 2.28%). Click the image and then the magnifying glass to see the image in full 4k resolution, if you have a 4k monitor.

Width of scene is 41 cm, as a reference (for the material). Camera focal length is 75 mm, to minimize geometric distortion.
Lighting: Large disc light from top (somewhat weak and distant, see faint shadow cast by the coil around the bottom of the metal pole in the center). Key light from front right, casting clearly visible shadows.

All of the translucent white plastic is just one material type, including the plastic rings around the metal pole's bottom, broken apart individually to the left of the pole to illustrate thickness. The material I came up with just looks too hard and plasticy.

« Last Edit: 2020-09-06, 19:29:28 by SharpEars »

2020-09-07, 02:04:34
Reply #4

burnin

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Silicone: IOR ~1.43, Abbe ~ 44.44.
Also, use anisotropy (consider manufacturing process).

2020-09-08, 00:07:06
Reply #5

SharpEars

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Silicone: IOR ~1.43, Abbe ~ 44.44.
Also, use anisotropy (consider manufacturing process).

OK, will add that in to see what affect it has and repost.

2020-09-08, 12:03:53
Reply #6

pokoy

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I had a go at this... my thoughts were:
- it's clearly transparent/refractive so you need to with the refraction route with absorption and scattering (vs fraction)
- there's some rayleigh scattering going on (at least that's what it look slike) where certain wavelengths within the media get scattered more, hence the yellow/blue coloring. For this, absorption color needs to be slightly yellow (if you want this to be more or less pronounced, increase or decrease saturation in absorption color to control this effect)
- the internal scattering is pretty visible so scattering color has to be bright (the brighter the longer it renders, unfortunately)

Attached is a scene for max 2017 and 2020, give it a try. There's also another material done with the fraction route (it can't do refraction but it turns out pretty milky, you can also mix refraction/fraction in one shader if you want).

Play with:
- glossiness
- absorption distance
- scattering color (this one controls the scattering within the material, also, if you want the material to have a tone instead of the yellow/blue absorption, use this one, set absorption color to have no saturation then)

I also did a 10 minutes render with caustics. While it obviously took longer and is still quite noisy, the material looked much better since internal reflection were much more realistic, particularly visible on the tubes.

I had to remove some of the objects and HDR used in my renders, but the scene includes some lighting and the rolls, sheet and tubes.

One thing - the material is really sensitive in terms of lighting so keep in mind that any test you do may change considerably with different lighting ;)

2020-09-08, 14:22:54
Reply #7

romullus

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This looks very nice and convincing material. Could you please attach screenshot with material settings for those with older 3ds max.
I'm not Corona Team member. Everything i say, is my personal opinion only.
My Models | My Videos | My Pictures

2020-09-08, 15:00:05
Reply #8

pokoy

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Sorry, not in the office right now, I'll post a 2016 scene later tonight. Or do you need 2014?

2020-09-08, 15:02:50
Reply #9

romullus

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Thanks, 2016 would do fine for me, but if you have such option, then 2014 would be even better, since i know there's few people still using it.
I'm not Corona Team member. Everything i say, is my personal opinion only.
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2020-09-08, 17:03:16
Reply #10

PROH

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Looks very convincing :) Since OP uses C4D, I think that a screenshot of the material settings would be great also.

Regards

2020-09-08, 18:32:33
Reply #11

pokoy

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Somehow missed that OP uses C4D. In that case I'll post a screenshot with color values... and 2014/2016 versions of the max file.

One thing I forgot to point out is that in Corona, surface and shading normals render differently with any sort of sss/translucency/absorption, so that you'll have to keep your geometry quite highres to avoid seeing faceted 'artefacts'. It's not visible in my render above, it's too low res and too noisy, but it can become visible in a cleaner highres...

2020-09-08, 19:20:53
Reply #12

pokoy

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I might not be able to post anything today anymore, I'm afraid it's going to be tomorrow... Sorry.

2020-09-08, 21:48:53
Reply #13

SharpEars

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I might not be able to post anything today anymore, I'm afraid it's going to be tomorrow... Sorry.

Thank you very very much for your post. Although the MAX scene file you provided doesn't have lighting that matches the image sample and is missing half the geometry (the interesting ones, too!), I was able to tweak it to get something comparable.

I then made a copy of all geometry and threw the best material I had come up with as of right now on the second set, to do a side by side comparison (for now with caustics enabled, for the utmost realism).

It's being rendered right now at 2160x1440px on my 💥BEAST💥 of a workstation (Crazy overclocked/water cooled 18/36 core 4.9 GHz constant speed Skylake X (i9-7980ex) with -1 AVX2 and 128 GB of RAM). and I will post the image (and the settings for both our materials) when it's done, so other can make use of them.

It's moving pretty slow due to caustics, I took the liberty of increasing the max trace level to 50, just in case, oh and of course I removed the ten minute time limit and set it to zero (= test of my patience). I'll wait for it to drop into the single digits before I kill it and give my PC a break (one of the cores is sitting at 90 degrees C, right now).

A wonderful scene file for testing things out.

I just wish all of the objects in the sample images were actually present in the scene. The following objects are missing:

- The large stroller cover looking thing at the top
- All three of the trinkets in the middle that are hard to describe as to what they actually are
- The antenna looking object protruding from the coil of hose (top left)

If you have a scene file with everything, and better yet with lighting that matches the sample images, I'd appreciate it and will re-render both your material and mine.

Updates, below:

- 10 Passes, 17 mins, 13.23% noise


Just realized that you had DOF enabled, now disabled (or my material set will be blurred and I don't want to play with the aperture/distance settings), and restarting the render...

Dropping to a region render of just a pair of coils, with the two different materials, but at a larger size. It's taking forever to clear with caustics turned on...
« Last Edit: 2020-09-08, 22:44:56 by SharpEars »

2020-09-08, 22:22:09
Reply #14

pokoy

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Hey! I mentioned in my first post that I removed some stuff for sharing. The geometry you are missing is from a model on GrabCAD, I can post a link tomorrow. Obviously, I can't redistribute the data, but you can download yourself, and there are many other well suited models over there.

The HDR used for lighting my test scene came from hdrihaven, these again are public domain but I decided to remove it nonetheless... will post a link, too.

Glad you found it useful!! It's really very sensitive to lighting but I think the general parameters are acceptable. Then again, lots are left to play with and I had a hard time deciding which exact settings to go with. But that's the beauty of the scattering feature.
The only thing that's odd is how much scattering differs with caustics with exactly the same settings. I'm not sure what's going on there.

Your machine sounds about 10 times faster than mine :D