[Bf-docboard] Bf-docboard Digest, Vol 124, Issue 11

Mon Jun 22 00:50:52 CEST 2015

OK, agree, so let's reformulate and try to improve the answer.
(Thank you for the opportunity !)

A manifold mesh is a mesh in which the structure of the connected
faces in a closed volume will always point the normals (and their
surfaces) to the outside or to the inside of the mesh without any
overlaps. If you recalculate those normals, they will always point at
a predictable direction (To the outside or to the inside of the
volume). When working with non-closed volumes, a manifold mesh is a
mesh in which the normals will always define two different and
non-consecutive surfaces.

A manifold mesh will always define an even number of surfaces.
-----------------

A non-manifold mesh is a mesh in which the structure of a
non-overlapped surface (based on it's connected faces) won't determine
the inside or the outside of a volume based on it's normals, defining
a  single surface for both sides, but ended with flipped normals.
When working with non-closed volumes, a non-manifold mesh will always
determine at least one discontinuity at the normal directions, either
by an inversion of a connected loop, or by an odd number of surfaces.

A non manifold mesh will always define an odd number of surfaces.

2015-06-21 7:00 GMT-03:00, bf-docboard-request at blender.org
<bf-docboard-request at blender.org>:
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>    1. Re: Bf-docboard Digest, Vol 124, Issue 10 (Ivan Paulos Tom?)
>    2. Re: Bf-docboard Digest, Vol 124, Issue 10 (gandalf3)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 20 Jun 2015 11:12:32 -0300
> From: Ivan Paulos Tom? <greylica at gmail.com>
> Subject: Re: [Bf-docboard] Bf-docboard Digest, Vol 124, Issue 10
> To: bf-docboard at blender.org
> Message-ID:
> 	<CA+Zt8s5uuhroeDWpc65pzJyeFivq6dL7E8d2jP8G7fQS-8EMUg at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> Hi friends !
>
> The question about double sided and single sided faces, and manifold
> or non-manifold meshes is related to it's normals.
>
> The normal of the face is the face that is shaded.
>
> Normals, are generally pointed to a single side of the objects. And
> normally, because of the shading, normals are pointed (when we have
> closed meshes) externally to the world.
>
> The standard in the majority of the softwares, is to have a single
> sided face (only one normal per face, which means that the materials
> assigned will only be detected and rendered at the normal direction),
> but for compatibility with game engines, we can make Blender have
> double sided faces too.
>
> A manifold mesh is a mesh which faces are completely pointing to the
> outside or to the inside of the mesh, if you recalculate those
> normals, they will always point at a single direction (outside or
> inside).
>
> A non-manifold mesh is a mesh in which we can't determine the outside
> and the inside of the mesh, because the normals will *always" point at
> diferent directions, and it doesn't matter if we recalculate them
> using a tool or flip them manually, due to the way that the structure
> of the mesh is conected.
>
> Cheers !
>
> 2015-06-20 7:00 GMT-03:00, bf-docboard-request at blender.org
> <bf-docboard-request at blender.org>:
>> Send Bf-docboard mailing list submissions to
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>> 	bf-docboard-owner at blender.org
>>
>> When replying, please edit your Subject line so it is more specific
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>>
>>
>> Today's Topics:
>>
>>    1. Some weak points in the documentation. (brasshat at core.com)
>>    2. Re: Some weak points in the documentation. (gandalf3)
>>    3. Re: Some weak points in the documentation. (brasshat at core.com)
>>    4. Re: Some weak points in the documentation. (brasshat at core.com)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Sat, 20 Jun 2015 00:21:12 -0400 (EDT)
>> From: brasshat at core.com
>> Subject: [Bf-docboard] Some weak points in the documentation.
>> To: "Blender Documentation Project" <bf-docboard at blender.org>
>> Message-ID: <65486.99.58.2.94.1434774072.squirrel at webmail.core.com>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>>
>>
>> Friends,
>>
>> While answering a question on Blender Stack Exchange,
>> I went looking for some things in the manual that I thought should be
>> there, but were not.
>>
>> 1) Any information on what Blender
>> considers to be an interior face. There was no entry in the glossary, and
>> doing a search using the parameter "interior faces" did not
>> provide any hits. The only explanation I located was in the tool tip,
>> where a hidden face is defines as a face where all of the edges of the
>> face have more than 2 face users.
>>
>> 2) I could also not find any
>> information on removing non-manifold bits of a mesh when I attempted to
>> search on "non manifold".
>>
>> Both interior faces
>> and? non-manifold are items in the select menu of the 3D viewport
>> header.
>>
>> I'd add them myself, but haven't been able to rustle up
>> enough time to learn to make the edits.
>>
>> Noel Stoutenburg
>> -------------- next part --------------
>> An HTML attachment was scrubbed...
>> URL:
>> http://lists.blender.org/pipermail/bf-docboard/attachments/20150620/74f28fa9/attachment.html
>>
>>
>> ------------------------------
>>
>> Message: 2
>> Date: Fri, 19 Jun 2015 23:44:55 -0700
>> From: gandalf3 <zzyxpaw at gmail.com>
>> Subject: Re: [Bf-docboard] Some weak points in the documentation.
>> To: Blender Documentation Project <bf-docboard at blender.org>
>> Message-ID: <55850BE7.4040103 at gmail.com>
>> Content-Type: text/plain; charset="windows-1252"
>>
>> On 06/19/15 21:21, brasshat at core.com wrote:
>>> Friends,
>>>
>>> While answering a question on Blender Stack Exchange, I went looking
>>> for some things in the manual that I thought should be there, but were
>>> not.
>>>
>>> 1) Any information on what Blender considers to be an interior face.
>>> There was no entry in the glossary, and doing a search using the
>>> parameter "interior faces" did not provide any hits. The only
>>> explanation I located was in the tool tip, where a hidden face is
>>> defines as a face where all of the edges of the face have more than 2
>>> face users.
>>>
>>> 2) I could also not find any information on removing non-manifold bits
>>> of a mesh when I attempted to search on "non manifold".
>>>
>>> Both interior faces and  non-manifold are items in the select menu of
>>> the 3D viewport header.
>>>
>>> I'd add them myself, but haven't been able to rustle up enough time to
>>> learn to make the edits.
>>>
>>> Noel Stoutenburg
>>>
>>>
>>> _______________________________________________
>>> Bf-docboard mailing list
>>> Bf-docboard at blender.org
>>> http://lists.blender.org/mailman/listinfo/bf-docboard
>> They are here:
>> http://blender.org/manual/modeling/meshes/selecting/advanced.html
>>
>> Not sure why 'non manifold' and 'non-manifold' don't turn up any
>> results, but 'manifold' gives some.
>>
>> --
>> -gandalf3
>>
>> -------------- next part --------------
>> An HTML attachment was scrubbed...
>> URL:
>> http://lists.blender.org/pipermail/bf-docboard/attachments/20150619/6c507218/attachment-0001.htm
>>
>>
>> ------------------------------
>>
>> Message: 3
>> Date: Sat, 20 Jun 2015 04:08:51 -0400 (EDT)
>> From: brasshat at core.com
>> Subject: Re: [Bf-docboard] Some weak points in the documentation.
>> To: bf-docboard at blender.org
>> Message-ID: <51458.99.58.2.94.1434787731.squirrel at webmail.core.com>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>>
>>
>> Gandalf3,
>>
>> Regarding your question:
>>
>>>? Not
>> sure why 'non manifold' and 'non-manifold' don't turn up any     results,
>> but 'manifold' gives some.
>>
>> I can't explain "non
>> manifold", but "non-manifold" does not appear, because in
>> every instance there is a space between the hyphen and the word
>> "manifold", , and if the search facilities are case sensitive,
>> both the initial letters N and M are capitalized, so "Non-
>> Manifold.
>>
>> Noel Stoutenburg
>> -------------- next part --------------
>> An HTML attachment was scrubbed...
>> URL:
>> http://lists.blender.org/pipermail/bf-docboard/attachments/20150620/80918aff/attachment-0001.htm
>>
>>
>> ------------------------------
>>
>> Message: 4
>> Date: Sat, 20 Jun 2015 04:27:38 -0400 (EDT)
>> From: brasshat at core.com
>> Subject: Re: [Bf-docboard] Some weak points in the documentation.
>> To: "Blender Documentation Project" <bf-docboard at blender.org>
>> Message-ID: <51715.99.58.2.94.1434788858.squirrel at webmail.core.com>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>>
>>
>> Ooops.?
>>
>> I didn't look closely enough. and found after
>> hitting the "send" button that this statement,
>>
>>>
>> both the initial letters N and M are capitalized, so "Non-
>>>
>> Manifold.
>>
>> is not accurate.
>>
>> Noel Stoutenburg
>> -------------- next part --------------
>> An HTML attachment was scrubbed...
>> URL:
>> http://lists.blender.org/pipermail/bf-docboard/attachments/20150620/19b23ce3/attachment-0001.htm
>>
>>
>> ------------------------------
>>
>> _______________________________________________
>> Bf-docboard mailing list
>> Bf-docboard at blender.org
>> http://lists.blender.org/mailman/listinfo/bf-docboard
>>
>>
>> End of Bf-docboard Digest, Vol 124, Issue 10
>> ********************************************
>>
>
>
> ------------------------------
>
> Message: 2
> Date: Sat, 20 Jun 2015 11:33:29 -0700
> From: gandalf3 <zzyxpaw at gmail.com>
> Subject: Re: [Bf-docboard] Bf-docboard Digest, Vol 124, Issue 10
> To: Blender Documentation Project <bf-docboard at blender.org>
> Message-ID: <5585B1F9.9070102 at gmail.com>
> Content-Type: text/plain; charset="windows-1252"
>
> On 06/20/15 07:12, Ivan Paulos Tom? wrote:
>> Hi friends !
>>
>> The question about double sided and single sided faces, and manifold
>> or non-manifold meshes is related to it's normals.
>>
>> The normal of the face is the face that is shaded.
>>
>> Normals, are generally pointed to a single side of the objects. And
>> normally, because of the shading, normals are pointed (when we have
>> closed meshes) externally to the world.
>>
>> The standard in the majority of the softwares, is to have a single
>> sided face (only one normal per face, which means that the materials
>> assigned will only be detected and rendered at the normal direction),
>> but for compatibility with game engines, we can make Blender have
>> double sided faces too.
>>
>> A manifold mesh is a mesh which faces are completely pointing to the
>> outside or to the inside of the mesh, if you recalculate those
>> normals, they will always point at a single direction (outside or
>> inside).
>>
>> A non-manifold mesh is a mesh in which we can't determine the outside
>> and the inside of the mesh, because the normals will *always" point at
>> diferent directions, and it doesn't matter if we recalculate them
>> using a tool or flip them manually, due to the way that the structure
>> of the mesh is conected.
> Well, it is possible to have non-manifold meshes with consistent normals
> (e.g. a 2D plane)
> And it's possible to have manifold geometry which cannot have consistent
> normals (e.g. a klien bottle <https://en.wikipedia.org/wiki/Klein_bottle>)
>
> So this definition doesn't hold up under all circumstances.
>
> The manual doesn't really attempt to define it beyond saying
> "non-manifold geometry cannot exist in the real world", but this too is
> slightly misleading (klien bottles are manifold, but they cannot exist
> in the real world because they intersect themselves).
> Perhaps it would be nice to write up a detailed explanation of all this
> on the manual somewhere (like this
> <http://blender.stackexchange.com/q/7910/599>, but better).
>
>>
>> Cheers !
>>
>> 2015-06-20 7:00 GMT-03:00, bf-docboard-request at blender.org
>> <bf-docboard-request at blender.org>:
>>> Send Bf-docboard mailing list submissions to
>>> 	bf-docboard at blender.org
>>>
>>> To subscribe or unsubscribe via the World Wide Web, visit
>>> 	http://lists.blender.org/mailman/listinfo/bf-docboard
>>> or, via email, send a message with subject or body 'help' to
>>> 	bf-docboard-request at blender.org
>>>
>>> You can reach the person managing the list at
>>> 	bf-docboard-owner at blender.org
>>>
>>> When replying, please edit your Subject line so it is more specific
>>> than "Re: Contents of Bf-docboard digest..."
>>>
>>>
>>> Today's Topics:
>>>
>>>     1. Some weak points in the documentation. (brasshat at core.com)
>>>     2. Re: Some weak points in the documentation. (gandalf3)
>>>     3. Re: Some weak points in the documentation. (brasshat at core.com)
>>>     4. Re: Some weak points in the documentation. (brasshat at core.com)
>>>
>>>
>>> ----------------------------------------------------------------------
>>>
>>> Message: 1
>>> Date: Sat, 20 Jun 2015 00:21:12 -0400 (EDT)
>>> From: brasshat at core.com
>>> Subject: [Bf-docboard] Some weak points in the documentation.
>>> To: "Blender Documentation Project" <bf-docboard at blender.org>
>>> Message-ID: <65486.99.58.2.94.1434774072.squirrel at webmail.core.com>
>>> Content-Type: text/plain; charset="iso-8859-1"
>>>
>>>
>>>
>>> Friends,
>>>
>>> While answering a question on Blender Stack Exchange,
>>> I went looking for some things in the manual that I thought should be
>>> there, but were not.
>>>
>>> 1) Any information on what Blender
>>> considers to be an interior face. There was no entry in the glossary,
>>> and
>>> doing a search using the parameter "interior faces" did not
>>> provide any hits. The only explanation I located was in the tool tip,
>>> where a hidden face is defines as a face where all of the edges of the
>>> face have more than 2 face users.
>>>
>>> 2) I could also not find any
>>> information on removing non-manifold bits of a mesh when I attempted to
>>> search on "non manifold".
>>>
>>> Both interior faces
>>> and? non-manifold are items in the select menu of the 3D viewport
>>> header.
>>>
>>> I'd add them myself, but haven't been able to rustle up
>>> enough time to learn to make the edits.
>>>
>>> Noel Stoutenburg
>>> -------------- next part --------------
>>> An HTML attachment was scrubbed...
>>> URL:
>>> http://lists.blender.org/pipermail/bf-docboard/attachments/20150620/74f28fa9/attachment.html
>>>
>>>
>>> ------------------------------
>>>
>>> Message: 2
>>> Date: Fri, 19 Jun 2015 23:44:55 -0700
>>> From: gandalf3 <zzyxpaw at gmail.com>
>>> Subject: Re: [Bf-docboard] Some weak points in the documentation.
>>> To: Blender Documentation Project <bf-docboard at blender.org>
>>> Message-ID: <55850BE7.4040103 at gmail.com>
>>> Content-Type: text/plain; charset="windows-1252"
>>>
>>> On 06/19/15 21:21, brasshat at core.com wrote:
>>>> Friends,
>>>>
>>>> While answering a question on Blender Stack Exchange, I went looking
>>>> for some things in the manual that I thought should be there, but were
>>>> not.
>>>>
>>>> 1) Any information on what Blender considers to be an interior face.
>>>> There was no entry in the glossary, and doing a search using the
>>>> parameter "interior faces" did not provide any hits. The only
>>>> explanation I located was in the tool tip, where a hidden face is
>>>> defines as a face where all of the edges of the face have more than 2
>>>> face users.
>>>>
>>>> 2) I could also not find any information on removing non-manifold bits
>>>> of a mesh when I attempted to search on "non manifold".
>>>>
>>>> Both interior faces and  non-manifold are items in the select menu of
>>>> the 3D viewport header.
>>>>
>>>> I'd add them myself, but haven't been able to rustle up enough time to
>>>> learn to make the edits.
>>>>
>>>> Noel Stoutenburg
>>>>
>>>>
>>>> _______________________________________________
>>>> Bf-docboard mailing list
>>>> Bf-docboard at blender.org
>>>> http://lists.blender.org/mailman/listinfo/bf-docboard
>>> They are here:
>>> http://blender.org/manual/modeling/meshes/selecting/advanced.html
>>>
>>> Not sure why 'non manifold' and 'non-manifold' don't turn up any
>>> results, but 'manifold' gives some.
>>>
>>> --
>>> -gandalf3
>>>
>>> -------------- next part --------------
>>> An HTML attachment was scrubbed...
>>> URL:
>>> http://lists.blender.org/pipermail/bf-docboard/attachments/20150619/6c507218/attachment-0001.htm
>>>
>>>
>>> ------------------------------
>>>
>>> Message: 3
>>> Date: Sat, 20 Jun 2015 04:08:51 -0400 (EDT)
>>> From: brasshat at core.com
>>> Subject: Re: [Bf-docboard] Some weak points in the documentation.
>>> To: bf-docboard at blender.org
>>> Message-ID: <51458.99.58.2.94.1434787731.squirrel at webmail.core.com>
>>> Content-Type: text/plain; charset="iso-8859-1"
>>>
>>>
>>>
>>> Gandalf3,
>>>
>>> Regarding your question:
>>>
>>>> ? Not
>>> sure why 'non manifold' and 'non-manifold' don't turn up any
>>> results,
>>> but 'manifold' gives some.
>>>
>>> I can't explain "non
>>> manifold", but "non-manifold" does not appear, because in
>>> every instance there is a space between the hyphen and the word
>>> "manifold", , and if the search facilities are case sensitive,
>>> both the initial letters N and M are capitalized, so "Non-
>>> Manifold.
>>>
>>> Noel Stoutenburg
>>> -------------- next part --------------
>>> An HTML attachment was scrubbed...
>>> URL:
>>> http://lists.blender.org/pipermail/bf-docboard/attachments/20150620/80918aff/attachment-0001.htm
>>>
>>>
>>> ------------------------------
>>>
>>> Message: 4
>>> Date: Sat, 20 Jun 2015 04:27:38 -0400 (EDT)
>>> From: brasshat at core.com
>>> Subject: Re: [Bf-docboard] Some weak points in the documentation.
>>> To: "Blender Documentation Project" <bf-docboard at blender.org>
>>> Message-ID: <51715.99.58.2.94.1434788858.squirrel at webmail.core.com>
>>> Content-Type: text/plain; charset="iso-8859-1"
>>>
>>>
>>>
>>> Ooops.?
>>>
>>> I didn't look closely enough. and found after
>>> hitting the "send" button that this statement,
>>>
>>> both the initial letters N and M are capitalized, so "Non-
>>> Manifold.
>>>
>>> is not accurate.
>>>
>>> Noel Stoutenburg
>>> -------------- next part --------------
>>> An HTML attachment was scrubbed...
>>> URL:
>>> http://lists.blender.org/pipermail/bf-docboard/attachments/20150620/19b23ce3/attachment-0001.htm
>>>
>>>
>>> ------------------------------
>>>
>>> _______________________________________________
>>> Bf-docboard mailing list
>>> Bf-docboard at blender.org
>>> http://lists.blender.org/mailman/listinfo/bf-docboard
>>>
>>>
>>> End of Bf-docboard Digest, Vol 124, Issue 10
>>> ********************************************
>>>
>> _______________________________________________
>> Bf-docboard mailing list
>> Bf-docboard at blender.org
>> http://lists.blender.org/mailman/listinfo/bf-docboard
>
>
> --
> -gandalf3
>
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> End of Bf-docboard Digest, Vol 124, Issue 11
> ********************************************
>