Two clear volumes in face contact

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Jan
Posts: 36
Joined: Sun Jan 10, 2021 2:37 pm

Re: Two clear volumes in face contact

Post by Jan » Tue Apr 27, 2021 12:50 pm

lighting_freak wrote:
Mon Apr 26, 2021 8:31 pm
Hello,

There are no overlapping surfaces in that model.
One of the two faces that are shared by both volumes is deleted (or better said: has never been imported).

The remaining surface (marked in red) carries an interior and exterior volume as mentioned in this image:
VOLUME_Setup.jpg

Well now we know that everything works as it should if you don't have any volume contact situation.
My work really needs some solution for that - we're dealing quite often with such geomterical setups.
Then where is the volume contact if "One of the two faces that are shared by both volumes is deleted"?
lighting_freak wrote:
Mon Apr 26, 2021 8:31 pm
Is this setup right in general if one wants to handle this volume contact case?
I'll just like to share it again with more precide naming:
Test_Scene.zip
With two faces deleted then there must only be three remaining faces? Can you show which two faces overlap each other?
lighting_freak wrote:
Mon Apr 26, 2021 8:31 pm
Jan wrote:
Sat Apr 24, 2021 2:06 pm
Refraction and Reflection on the 2nd Glass Object below the First Glass Object no longer works if Faces are flipped
I think if you start flipping the face normals (see the arrows in the image) the algorythm will be confused with what is inside an outside of the volume.

With kind regards
I think there is anomaly with the laser light itself. It's choosy on the face orientation. Let me put it in another post.

Best Regards

lighting_freak
Posts: 233
Joined: Thu Jan 18, 2018 6:02 pm

Re: Two clear volumes in face contact

Post by lighting_freak » Thu Apr 29, 2021 8:12 pm

Hello
Jan wrote:
Tue Apr 27, 2021 12:50 pm
Then where is the volume contact if "One of the two faces that are shared by both volumes is deleted"?
Imagine a cube and delete one of it's faces.
The result is kind of a shell, like this.
cube_shell_1.jpg
All remaining face normals point to air.

And another cube, that is turned into shell with deleted opposite face:
cube_shell_2.jpg
Both are connected by a single (not overlapping) face in the middle:
cube_shell_3.jpg
The normal of that face points to one of the cubes and that indicates the exterior volume.

With kind regards.
OS - Windows 7 X64
CPU - Intel CORE i7
GPU1 - Variants of notebook card from nVidia
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Jan
Posts: 36
Joined: Sun Jan 10, 2021 2:37 pm

Re: Two clear volumes in face contact

Post by Jan » Fri Apr 30, 2021 5:16 am

Hi,

Thanks for the illustration. Now I think the issue is no longer cause by overlapping faces. It's very similar to my issue that I have posted with inverted faces. Please check the comparisons below.

Reference Single Object - - Ray Tracing
single object.jpg

Your Original Test Scene Setup with Face Elements Spread Out - Solid Illustration
2 faces with interfaec_Solid.jpg

Your Original Test Scene Setup with Face Elements Spread Out - Ray Tracing
2 faces with interface.jpg

Less the Interface - Ray Tracing
2 faces without interface.jpg
Attachments
test scene with comparisons.blend
(1.03 MiB) Downloaded 59 times

lighting_freak
Posts: 233
Joined: Thu Jan 18, 2018 6:02 pm

Re: Two clear volumes in face contact

Post by lighting_freak » Thu May 13, 2021 7:43 pm

Hello all,

I wonder whether there are any further actions on that topic.

I mean now its clear that is not a matter of overlapping faces...
Also not a matter of wrong volume definition...

Kind regards
OS - Windows 7 X64
CPU - Intel CORE i7
GPU1 - Variants of notebook card from nVidia
GPU2 - Variants of notebook onboard card from Intel
Lux - Latest possible relaease

lighting_freak
Posts: 233
Joined: Thu Jan 18, 2018 6:02 pm

Re: Two clear volumes in face contact

Post by lighting_freak » Wed May 26, 2021 3:37 pm

Hello,

I know that it's not very kind to simply reask the questions but I'm dealing with optical materials that are sticked to each other quite often.

I could really use some support on that topic. As already described it's not a matter of overlapping faces and also not a matter of volume/face normals direction.

Please help me on this topic.
Thank you in advance.

With kind regards
OS - Windows 7 X64
CPU - Intel CORE i7
GPU1 - Variants of notebook card from nVidia
GPU2 - Variants of notebook onboard card from Intel
Lux - Latest possible relaease

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fluxfish
Posts: 8
Joined: Thu Aug 09, 2018 9:27 pm

Re: Two clear volumes in face contact

Post by fluxfish » Sat Jul 24, 2021 2:40 pm

Dade wrote:
Mon Apr 19, 2021 6:12 pm
Jan wrote:
Mon Apr 19, 2021 4:30 pm
As I said in my previous post strange artifacts happens if two surfaces overlap. A tiny gap of 0.1mm resolve the issue.
It is just 32bit floating point (lack of) precision as I have already explained lighting_freak multiple times in the past. You can not have overlapping surfaces, you have to use a single surface and appropriate interior/exterior volumes.
Hmmm, IMHO the issues are quite difficult to manage for a user. It's a good and comfortable starting point if you have a scene natively created within Blender (e.g.), but nowadays often you have or want to deal with provided data and imported meshes, maybe some technical CAD-based data of Solidworks, CATIA, ..well, whatever the data-origin is.
It might happen that there are 2 volumes with touching (identical) surfaces but the triangulated data contain 2 meshes with sharing surfaces which still might be digitally different.
The question is how to deal with these digital differences of assumed 'identical surfaces'.
As far as I know a well working approach during raytracing is to work with point-distance-limits, so that intersections get handled as being identical if below a defined distance/value, and same with surface-normals, managing their tangency.
That make sense, there might be precision- or mesh-'flaws' you are still not aware of..and you might still not be interested in.

@lighting_freak
honestly, I thought your 1st pictures a bit irritating to catch the concern, you can still see a lot of irritating environment-reflections (due to fresnel), you are able to see the corners of your cube, then no arrows or anything to focus on. That is still okay, but well..happens often here and there in the forum.

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