Skin modifier root exploit #45669

New Issue

Karja Krähwald · 2015-08-04T01:00:32+02:00

Karja Krähwald commented

2015-08-04 01:00:32 +02:00

System Information
Windows 7 64, GTX 980

Blender Version
Broken: c27589e + 00857be

Short description of error
There is an exploit that allows to create more than 1 root on a connected surface with the skin modifier.

Wiki says for skin modifiers root:

Each set of connected vertices should have one root node. Mark Root enforces the one-root per set rule, so it is not necessary to manually unmark roots.

Since an exploit is sort of a bug, I think its not wrong to report it.
Its behaviour is definitely not intended - one-root per set rule is broken.
But I also want to point out that this "bug" is quite friendly and useful for modeling.
Please take a look in the file.

Exact steps for others to reproduce the error
SkinModRootExploit.blend

**System Information** Windows 7 64, GTX 980 **Blender Version** Broken: c27589e + 00857be **Short description of error** There is an exploit that allows to create more than 1 root on a connected surface with the skin modifier. Wiki says for skin modifiers root: > Each set of connected vertices should have one root node. Mark Root enforces the one-root per set rule, so it is not necessary to manually unmark roots. Since an exploit is sort of a bug, I think its not wrong to report it. Its behaviour is definitely not intended - one-root per set rule is broken. But I also want to point out that this "bug" is quite friendly and useful for modeling. Please take a look in the file. **Exact steps for others to reproduce the error** [SkinModRootExploit.blend](https://archive.blender.org/developer/F218551/SkinModRootExploit.blend)

Karja Krähwald commented

2015-08-04 01:00:32 +02:00

Changed status to: 'Open'

Karja Krähwald commented

2015-08-04 01:00:32 +02:00

Added subscriber: @karja

Sergey Sharybin commented

2015-08-04 11:40:42 +02:00

Added subscribers: @mont29, @ideasman42, @Sergey

Sergey Sharybin commented

2015-08-04 11:40:42 +02:00

@ideasman42, @mont29 any ideas here?

Bastien Montagne commented

2015-08-05 14:51:45 +02:00

So basically, we should be able to have several roots per mesh, as long as we only have one root per mesh 'island'… Does make sense to me, but will let @ideasman42 decide here, afaik he maintains that modifier.

Bastien Montagne commented

2015-08-05 14:57:06 +02:00

Actually, to be precise, user here want to be able to define roots for 'fake' islands generated by hidden geometry… So on second thought, not sure we want to support that. Which also means we should check when merging different islands of a same mesh (or different meshes), that we only keep one root… Meh, this is serious corner-case. :|

Karja Krähwald commented

2015-08-05 21:28:45 +02:00

I was not sure where to put this. I guess it looks way more like a feature request, but I found it very surprising or contradictary that the modifier is still working properly with multiple roots, although it deletes all previous with the root button.

Campbell Barton commented

2015-08-29 06:44:47 +02:00

Changed status from 'Open' to: 'Archived'

Campbell Barton closed this issue

2015-08-29 06:44:47 +02:00

Campbell Barton self-assigned this 2015-08-29 06:44:47 +02:00

Campbell Barton commented

2015-08-29 06:44:47 +02:00

Hi @karja, I see you put quite some effort into this report,

On checking the use-case, its really quite obscure that you would choose to hide some parts of geometry - just so you can cause an island - in what is not initially an island. (using the mask modifier).
While there would undoubtedly be some use case for this. It seems rather contrived.

We could drop the requirement and allow multiple roots on a single mesh island... but this is going to cause problems (odd behavior at least) as well.

So I'm going to close this bug, currently this is working as intended.

Hi @karja, I see you put quite some effort into this report, On checking the use-case, its really quite obscure that you would choose to hide some parts of geometry - just so you can cause an island - in what is not initially an island. (using the mask modifier). While there would undoubtedly be some use case for this. It seems rather contrived. We could drop the requirement and allow multiple roots on a single mesh island... but this is going to cause problems (odd behavior at least) as well. So I'm going to close this bug, currently this is working as intended.

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Skin modifier root exploit #45669