Random per island help please

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sarmath
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Random per island help please

Post by sarmath » Thu Oct 15, 2020 1:19 pm

Hi

I am trying to use random per island in Blender 2.83 and luxcore 2.4 and it seems to not work for me.
This is test scene, can someone confirm what I am doing wrong or is it somehow broken thanks.
randomperisland.blend
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Windows 10 Pro Ryzen 9 3900x 2xGTX 1070ti 32 GB RAM

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B.Y.O.B.
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Re: Random per island help please

Post by B.Y.O.B. » Thu Oct 15, 2020 2:33 pm

The random per island shape code performs a "merge doubles" operation before detecting the islands: https://github.com/LuxCoreRender/LuxCor ... pe.cpp#L43
This should probably be removed for this shape (Cycles doesn't do this).

sarmath
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Re: Random per island help please

Post by sarmath » Thu Oct 15, 2020 3:20 pm

I have merged the doubles but still no effect like in sharlybg tutorial:
https://www.youtube.com/watch?v=NO9VE2SxXm0

Still cant figure it out ...maybe sharlybg can check it??
Windows 10 Pro Ryzen 9 3900x 2xGTX 1070ti 32 GB RAM

AndreasResch
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Re: Random per island help please

Post by AndreasResch » Wed Mar 03, 2021 7:31 am

The initial issue that I had was, that the term "island" is usually used in conjunction with UV islands, which the original poster also seemed to have thought (looking at his file). Aside from that, there really seems to be an issue if the polygon island is just split from the rest of the geometry but isn't moved. As soon as the the split polygons are moved away from the rest of the geometry, the RPI node works. Maybe worth looking into that "double merge" issue.
Last edited by AndreasResch on Wed Mar 03, 2021 12:33 pm, edited 1 time in total.

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Dade
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Re: Random per island help please

Post by Dade » Wed Mar 03, 2021 10:18 am

AndreasResch wrote:
Wed Mar 03, 2021 7:31 am
The initial issue that I had was, that the term "island" is usually used in conjunction with UV islands, which the original poster also seemed to have thought (looking at his file). Aside from that, there really seems to be an issue if the polygon island is just split from the rest of the geometry but isn't moved. As soon as the the split polygons are moved away from the rest of the geometry, the RPI node works. Maybe worth looking into that "double merge" issue.
This is intended: overlapped edges are considered the same. 2 edges are considered overlapped if the distance of their vertices is less than an epsilon (i.e. something like a 0.00001 meters).
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B.Y.O.B.
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Re: Random per island help please

Post by B.Y.O.B. » Wed Mar 03, 2021 10:49 am

Maybe the "remove doubles" step could be made optional?
In the Blender addon it would be disabled then, to make the behaviour the same as in Cycles.

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Dade
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Re: Random per island help please

Post by Dade » Wed Mar 03, 2021 10:54 am

B.Y.O.B. wrote:
Wed Mar 03, 2021 10:49 am
Maybe the "remove doubles" step could be made optional?
In the Blender addon it would be disabled then, to make the behaviour the same as in Cycles.
It isn't possible (i.e. meshes split by materials, quads split in 2 triangles, etc.). It is something has been already discussed in the original Island thread.
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