Transparent material to dark

General discussion about Indigo Materials - material requests, material developement, feedback, etc..
Post Reply
11 posts • Page 1 of 1
nPenrod
Posts: 5
Joined: Wed Jan 22, 2014 6:25 am

Transparent material to dark

Post by nPenrod » Wed Jan 22, 2014 6:35 am

I am trying to render a transparent volume. The shape is transparent but seems really dark. I have turned off the absorption layer in the material and have set the absorption coefficient in the medium to 0. I'm not sure where else to look. What other factors affect volume transparency?

I am using Indigo 3.6.26.
Attachments
Transparent.png
Test render

User avatar
galinette
1st Place Winner
Posts: 923
Joined: Sat Jan 09, 2010 1:39 am
Location: Nantes, France
Contact:

Re: Transparent material to dark

Post by galinette » Wed Jan 22, 2014 9:55 am

Transparent materials rendering black are often due to non-closed volumes, or normal orientation issues.

Check that:
- The transparent material volume is made of a closed geometry
- The material is applied to the whole closed geometry
- Normals point outwards

Etienne
Eclat-Digital Research
http://www.eclat-digital.com

nPenrod
Posts: 5
Joined: Wed Jan 22, 2014 6:25 am

Re: Transparent material to dark

Post by nPenrod » Wed Jan 22, 2014 2:46 pm

Is there a good way to test for open geometry or bad normals? I am using some geometry I generated in code, as well as some geometry that I imported from blender and both look the same. Is it safe to assume that the blender geometry is correct?

nPenrod
Posts: 5
Joined: Wed Jan 22, 2014 6:25 am

Re: Transparent material to dark

Post by nPenrod » Sun Jan 26, 2014 9:32 am

Playing around with this some more it looks like my transparent geometry might also be casting shadows in the scene. is this normal behavior? Can I disable it?

User avatar
fenerolina
Posts: 141
Joined: Sun Mar 15, 2009 12:27 pm
Location: Pyrenees

Re: Transparent material to dark

Post by fenerolina » Sun Jan 26, 2014 10:38 am

Which software are you using? share your file and someone might have a look.

User avatar
CTZn
Posts: 7240
Joined: Thu Nov 16, 2006 4:34 pm
Location: Paris, France

Re: Transparent material to dark

Post by CTZn » Fri Feb 14, 2014 2:27 am

it's not safe to assume that a procedural geometry will result clean unless if the generating algorithm has such dedicated routines.
You could try to merge vertices under a certain threshold distance, close holes and eventually conform normals.
obsolete asset

nPenrod
Posts: 5
Joined: Wed Jan 22, 2014 6:25 am

Re: Transparent material to dark

Post by nPenrod » Wed Feb 26, 2014 5:52 am

OK, so I finally put together some test scenes that better illustrate my issue. I have two images here, a solid sphere encapsulated in a transparent sphere. In the first image the transparent sphere is small and creates a thin layer of glass around the solid sphere. In the second image the transparent sphere is much larger and creates a thick layer of glass. The apparent light loss, or color change, is the same in both cases. I would expect the color shift to be dependent on the thickness or radius of the transparent sphere but that doesn't seem to be the case. I'd like to create a smoother transition between the clear and solid surfaces if possible.

In the process of experimenting with this I noticed another strange anomaly. If I enable displacement mapping on the transparent surface the position of the specular highlights shifts slightly to the left, even if the displacement value is set to zero. Based on the equation in the manual I would expect to see no change.
smallSphere.png
small glass sphere
largeSphere.png
large glass sphere
displacement.png
displaced highlights
Attachments
indigo test scenes.zip
test scenes
(105.91 KiB) Downloaded 228 times

FakeShamus
Posts: 512
Joined: Wed May 02, 2007 11:34 am

Re: Transparent material to dark

Post by FakeShamus » Wed Feb 26, 2014 6:44 am

For the transparency issue, try rendering using BiDir and glass acceleration turned on (or with the new beta release, use arch glass option on your transparent medium)
not sure about the displacement question you mentioned.
Attachments
largeSphere_accel.png

nPenrod
Posts: 5
Joined: Wed Jan 22, 2014 6:25 am

Re: Transparent material to dark

Post by nPenrod » Tue Mar 04, 2014 6:50 am

Glass acceleration doesn't seem to help much for curved glass. The new arch glass option helps the color, but removes all of the refraction caused by the transparent surface.

User avatar
Headroom
Indigo 100
Posts: 1058
Joined: Wed Aug 08, 2007 1:07 pm
Location: Spartanburg, SC, USA
Contact:

Re: Transparent material to dark

Post by Headroom » Tue Mar 04, 2014 12:19 pm

It has been asked before: What modeling software do you use ?

If you post scenes, then post them in the native format of your modeling software. Otherwise it is very difficult to determine what went wrong.

User avatar
dakiru
Indigo 100
Posts: 747
Joined: Mon Jun 22, 2009 6:51 am

Re: Transparent material to dark

Post by dakiru » Wed Mar 05, 2014 2:52 pm

It could be scale. Here is the glass 200mm*200mm*4mm, scale 1
scale_1.png
scale_1.png (36.54 KiB) Viewed 6393 times
scale 1000, so the glass becomes four meters thick
scale_1000.png
scale_1000.png (37.21 KiB) Viewed 6393 times

Post Reply
11 posts • Page 1 of 1

Who is online

Users browsing this forum: No registered users and 23 guests