[Bf-committers] Updated BMesh Merge Proposal

[Campbell Barton]

Follow up on the forward compatibility topic.
Ton and I agreed on the following 2 solutions.

1) BMesh has an option to save as `Legacy mesh format`. so files could
load in 2.4x if you really wanted.

2) 2.62 will load BMesh files (where 2.60 and older will crash unless
the legacy option is set).


Both are now implemented in trunk/bmesh, luckily they both use the
same MPoly --> MFace function so it wasn't a lot of extra work.
NGons are simply ignored in non BMesh versions of blender.

2011/12/3 Campbell Barton <ideasman42 at gmail.com>:
> There are many options here, I was going to list all the ones I could
> think of but most have some fairly annoying drawbacks.
>
> Currently BMesh triangulates the mesh when loaded in trunk or 2.4x,
>
> You could argue both ways...
>
> since mesh data is core to most blender projects...
> a) being forwards compatible highly important.
> b) triangulation of quads is so destructive - users would be better
> off exporting to an intermediate format then using new blendfiles in
> an older blender.
>
> Not crashing gives the appearance of working but infact its still
> quite limited, people aren't seriously going to take meshes with UV's,
> vertex colors etc and load them in an older blender to continue
> working.
>
>
> IMHO possible practical options are...
>
> * do nothing (allow crashing).
>
> * solve crash loading bmesh files for 2.61+, this ofcourse wont help
> 2.60 or older but at least allows loading in a few previous releases.
>
> * make a token effort - (what I'm proposing, load in triangulated mesh data)
>
> * write full edge and face data into the file (would make file larger
> since it would need to save faces twice, not to mention uv, vertex
> color layers etc, also if quite some work to do this and know to
> ignore edge data which doesn't exist for ngons).
>
> * New save option/mode "Save as 2.60 compatible blend" as suggested,
> I'm not keen on this option, mainly because it introduces the overhead
> of having multiple ways to save a blend file and gives us more work to
> support, but it could be made to work well and at least wont slow down
> regular saving as with what I suggested initially.
>
> On Fri, Dec 2, 2011 at 11:25 PM, Knapp <magick.crow at gmail.com> wrote:
>> One other idea just jumped up at me. Write a python add on for the old
>> software that would allow for loading of the new format. Then users of
>> 2.4 or whatever can download it and add it to their old blender.
>>
>> On Fri, Dec 2, 2011 at 1:22 PM, Knapp <magick.crow at gmail.com> wrote:
>>> 2011/12/2 Αντώνης Ρυακιωτάκης <kalast at gmail.com>:
>>>> Well, what about earlier versions of blender? They won't have the
>>>> newer version checking code. But I like the idea of exporting
>>>> function, or something close.
>>>
>>> Yes, that is true but the idea does fix the problem for the next time
>>> it comes up, as it will, in the future.
>>>
>>> And the export function should make it possible to give the old
>>> software the new blends but that leaves the old programs with the new
>>> files problem.
>>>
>>> Perhaps this is not ideal but could the new blends be made so that
>>> there is no chance that the old software can load them? That should
>>> block complaints other than it will not load, at which point we can
>>> just tell them to get the new software and export to the old format.
>>>
>>> --
>>> Douglas E Knapp
>>>
>>> Creative Commons Film Group, Helping people make open source movies
>>> with open source software!
>>> http://douglas.bespin.org/CommonsFilmGroup/phpBB3/index.php
>>>
>>> Massage in Gelsenkirchen-Buer:
>>> http://douglas.bespin.org/tcm/ztab1.htm
>>> Please link to me and trade links with me!
>>>
>>> Open Source Sci-Fi mmoRPG Game project.
>>> http://sf-journey-creations.wikispot.org/Front_Page
>>> http://code.google.com/p/perspectiveproject/
>>
>>
>>
>> --
>> Douglas E Knapp
>>
>> Creative Commons Film Group, Helping people make open source movies
>> with open source software!
>> http://douglas.bespin.org/CommonsFilmGroup/phpBB3/index.php
>>
>> Massage in Gelsenkirchen-Buer:
>> http://douglas.bespin.org/tcm/ztab1.htm
>> Please link to me and trade links with me!
>>
>> Open Source Sci-Fi mmoRPG Game project.
>> http://sf-journey-creations.wikispot.org/Front_Page
>> http://code.google.com/p/perspectiveproject/
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>
>
>
> --
> - Campbell



-- 
- Campbell