[Bf-animsys] proposal: Better F-Curve auto handle calculation

[Joshua Leung]

Hi,

I thought most of the discussion for this was already happening in the
tracker report for this. I'm all in favour of stuff that makes life for
animators easier - in particular, if it's something that happens a lot (as
is the case here).

Last time I checked, my main concern was regarding backwards compatability.
Specifically, although it only modifies old curves when handle recalc
occurs, care is needed as handle recalc doesn't only occur when editing the
curve - for instance, it can also happen when NLA time remapping occurs
(e.g. entering/exiting tweakmode on a NLA strip), and probably a few other
cases too.

(EDIT: The per-curve option mentioned on the Graphicall build probably
resolves the backwards compat/handle-editing problem, though the devil is
in the details :)

On another note, there's another patch floating around that deals with
similar issues (or rather, only the case where the user is inserting a new
keyframe).
    https://developer.blender.org/D2642
I'd be curious to hear from animators who've tried D2642 how effective it
is, and/or whether it'd still be necessary in light of these handle
calculation changes.


Regards,
Joshua


On Wed, Aug 9, 2017 at 10:42 PM, Sergey Sharybin <sergey.vfx at gmail.com>
wrote:

> Hi,
>
> It is hard to justify how well it'll sustain all possible animation
> scenarios. Now when we're at BCon1, maybe we can be relaxed and merge the
> code to master?
>
> On Wed, Aug 9, 2017 at 11:06 AM, Ton Roosendaal <ton at blender.org> wrote:
>
>> Hi all,
>>
>> This proposal went unreplied to, but I think it's important to give
>> proper attention.
>>
>> Doc and picture is here. It's actually quite obvious.
>> http://graphicall.org/1221
>>
>> I coded the old auto handle. It was an invention back then (no other sw
>> had it), and I simply put the the handle points parallel to the line
>> between the prev/next control point. Although that creates satisfying
>> circles, it fails to interpolate well. This patch solves this, without
>> breaking Blender (only on editing curves the handles re-cacalc).
>>
>> Thanks,
>>
>> -Ton-
>>
>> --------------------------------------------------------
>> Ton Roosendaal  -  ton at blender.org   -   www.blender.org
>> Chairman Blender Foundation, Director Blender Institute
>> Entrepotdok 57A, 1018 AD, Amsterdam, the Netherlands
>>
>> On 16 May 2017, at 10:27, Alexander Gavrilov <angavrilov at gmail.com>
>> wrote:
>>
>> Hello,
>>
>> It's known that the way auto handles work in blender curves isn't great,
>> and there
>> have been complaints that animators are often forced to either manually
>> adjust all
>> curve handles, or bypass interpolation by keyframing every frame manually.
>>
>> Obviously, automatic interpolation can't hope to produce better animation
>> than
>> a human, but it should be usable when absolute top quality is not
>> required.
>> Thus I have taken a somewhat old patch by Benoit Bolsee that implements a
>> mathematical approach that produces smooth F-Curves and did some rewriting
>> and adding features to get it working solidly.
>>
>>
>> However since I'm not an animator I cannot evaluate myself how well these
>> new auto-handles would work in practical workflows, and how significant is
>> the improvement in the interpolated motion compared to the old way.
>>
>> One possible point of contention might be that producing smooth curves
>> necessarily
>> means that modifying keys affects the curve even at some distance from
>> the affected
>> key (although the degree of changes drops exponentially with distance,
>> and propagation
>> is completely stopped by Auto Clamped extremes or manual handles.)
>>
>> Also the degree this affects existing animations would determine how much
>> attention
>> to backward compatibility would be needed if this is adopted in 2.8:
>> should it e.g.
>> implement a legacy mode for curves created in previous versions with an
>> explicit
>> upgrade operation, or keep the shape until the curve is modified, or just
>> recalculate
>> shape etc.
>>
>>
>> I have uploaded a windows build of this branch (based on master for ease
>> of
>> testing) to GraphicAll, with more details on the design in the
>> description:
>>
>> http://graphicall.org/1221
>>
>> The build there can open master branch files without problems, and the
>> handles on
>> curves are only updated when the curve is touched by a modification
>> operation
>> (even if it is cancelled like G Esc), which may aid comparing.
>>
>> Alexander
>>
>> _______________________________________________
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>> Bf-animsys at blender.org
>> https://lists.blender.org/mailman/listinfo/bf-animsys
>>
>>
>>
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>>
>>
>
>
> --
> With best regards, Sergey Sharybin
>
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