[Bf-modeling] Proportional Edit Mode (Connected)

[Howard Trickey]

On Mon, Jun 17, 2013 at 8:52 AM, Campbell Barton <ideasman42 at gmail.com>wrote:

> Hi, There are cases where the current proportional edit-mode
> 'Connected' option doesn't give a nice smooth result across a grid for
> example.
>
> For details see the 2 links below, but these images sum up the problem
> quite well:
> *
> http://projects.blender.org/tracker/download.php/9/498/35590/25506/ProportionalEditingBug.png
>
> * http://i.imgur.com/U5TZW3i.png
>
>
>
> Details... previous discussion and bug report:
> *
> http://projects.blender.org/tracker/index.php?func=detail&aid=35590&group_id=9&atid=498
>
> * http://markmail.org/message/zkon53qzx32b5xek
>
>
>
> Probably long discussion is not needed about this.
>
> I think there are 2 obvious options....
>
> 1) Accept that connected works like this, just close the bug and tell
> users it known limitation with current design.
>
> 2) Add a second "Connected" option, so we have...
> * "Connected (Topology)" --- what we have now.
> * "Connected (Distance)" --- the real distance would work like it did
> many years ago, so only connected geometry is effected, but that
> geometry uses the distance between the 2 points without measuring
> along the topology.
>
> {for a less obvious option}
>
> 3) we could keep the options as they are now, but make "Connected"
> work without giving ugly artifacts,
> ... For example rather them simply measuring along edges we could
> measure across faces too... this would take longer to do and not
> necessarily give perfectly smooth results, but could still be worth
> looking into.
>

I think this 'across-face' rule could possible work.  After all, the
vertices
ARE connected via the face so it makes sense that the distance across
the face should be what is measured for the strength of the effect.
When I first read this, I though that it would destroy the use case in this
mail:
http://lists.blender.org/pipermail/bf-committers/2013-April/039799.html
 -- that is, a long chain of vertices that form a path that comes
near itself distance-wise but not topologically, and you only want to
affect the ones that are near topologically. But here there are no faces
across which the vertices that are 'near distance-wise' are near across.
Even if you changed the long chain of vertices into a long strip of quads,
the same argument would hold.

I think what we would really like is that proportional edit measures
real distances that follow the surface of the mesh, as short as possible
following that rule.  If there are no faces, it would have to follow edges,
but measure the length along those edges.

But this might be hard to calculate, especially if the mesh is non-manifold.
There may be multiple paths between two points, complicating things even
further.

If we don't want to go down the path of trying to implement that, I would be
in favor of option 2.  Or maybe a variant of that where you provide a slider
that goes from 0->1 to say what proportion to consider topological distance
vs distance in 3-space.


>
> --
> - Campbell
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