[Bf-animsys] 2.5 animsys overview + NLA "Bag" proposal

[Nathan Vegdahl]

   Thanks for the summary, Ton.  I think this is good to look again at
the current state of the system, so we're all on the same page.

   Firstly, I want to point out what an awesome job Aligorith has done
with this.  I've been jumping all over him lately (sorry Ali!) without
taking the time to acknowledge the kick-ass stuff he's already done.

   One of the thing that's really cool about this system is that it's
so flexible.  In fact, it's such a solid base that I imagine we could
layer just about any user-level paradigm on top of this.

   The IRC meetings were largely (entirely?) about what this
user-level paradigm should be.  How will actions and the NLA system
work from the user perspective?  If anyone cares to read them, here
are the IRC logs:

http://storage.cessen.com/temp/nla_chat.txt
http://storage.cessen.com/temp/nla_chat_2.txt

   Presently the most relevant thing from those meetings was the early
decision to use a "select/create action --> then animate" workflow.
The key points of this workflow are:

1. Actions are treated as first-class citizens.  For example: just
like objects, you manually create and delete actions.
2. There is always a single "active" action.
3. When you animate, it goes into the currently active action.

> And of course, a nice 'merge' or 'meta' operator then can
> create the much wanted "Ipo Bag", which should be named
> NLA bag I guess... :)

   I don't think meta-strips are a good substitute for Ipo bags.  For
one thing, due to possible blending/mixing/transitions within a
metastrip, there is no guarantee you can edit them directly as an
action.
   Also, if we depend on meta-strips for Ipo Bag functionality, how do
we then visualize meta-strips in the Graph and Action editors?  Do the
graph and action editors then get redefined to visualize NLA
timelines?  How is that going to be made simple and understandable for
the user?

   At the very least I don't want to have to jump through hoops to use
Ipo bag functionality, because for me it is a common and primary
use-case, not a secondary curiosity.  IMO it should be as easy and
simple as possible.
   Speaking for myself, I would ideally like *all* actions to be Ipo
bags, because that's as simple as it gets.  I would love for "action"
and "Ipo bag" to be synonyms, honestly.  And the system Aligorith has
written is easily capable of that by simply linking all actions to the
scene.

--Nathan V

On Wed, May 6, 2009 at 7:31 AM, Ton Roosendaal <ton at blender.org> wrote:
> Hi all,
>
> I've spent time with Joshua in irc to get a clear picture to present
> here.
> The first three points represents what Joshua already coded, or
> intended to make.
>
> 1)
>
> Here's the basic structure of the new anim system:
> http://download.blender.org/institute/animsys.png
>
> (For non coders: "Pointer" means "Using". A single Action or Material
> can be re-used all over in Blender, this linkage we do in C code with
> pointers. :)
>
> Each of Blender's "Library" data blocks, which have a relinkable
> generic "ID" header, now also have an AnimData extension. It's
> implemented for about 10 types now, including the Scene ID block (not
> in diagram).
>
> Let's call these things "ID blocks" and not "data blocks" to
> distinguish them from all smaller data segments in Blender (bones,
> constraints, and so on).
>
> The "AnimData" blocks are generic containers appended to ID blocks,
> where the Actions can get linked, and where drivers/nla/expressions
> reside.
>
> The new "Action" is a relinkable container of rna paths and fcurves. An
> rna path is a string that can find any data, including all bones,
> modifiers, constraints, and so on.
>
> However! It requires the right context to work, with the linked "ID"
> defining the starting point, from which rna paths can figure where to
> apply fcurves at.
> This means that an Action linked to Object, can have fcurves affecting
> a material. But, such Actions won't do much when directly linked to a
> Mesh or Material itself.
>
> Sofar it's clear I hope!
>
> 2)
>
> Let's zoom in on a single ID block with NLA:
> http://download.blender.org/institute/animsys1.png
>
> The NLA consists of 'strips', which each can link to an Action. The
> strip defines time, scaling of time, blending, etc.
>
> Note that an Action can also be directly linked to AnimData now, which
> will always be executed now, with NLA being acting on top of it,
> replacing it (if it works on same data).
>
> 3)
>
> We zoom out again:
> http://download.blender.org/institute/animsys2.png
>
> Here we see a single hierarchy of ID data, with two levels of NLA
> working.
> Actions or NLA used this way will allow localizing things nicely.
>
> However, we still are too limiting for our animators. They want one
> strip to control a complete massive warrior battle, right!
>
> 4)
>
> For (at least) Scenes and Groups, we can allow any strip to have own
> local "ID context".
> http://download.blender.org/institute/animsys3.png
>
> The NLA editor can nicely visualize it, and allow editing every strip.
> And of course, a nice 'merge' or 'meta' operator then can create the
> much wanted "Ipo Bag", which should be named NLA bag I guess... :)
>
> How modifiers, walk/strides etc will fit in I didn't look at yet. Let's
> first check if this could be a good basic to further work with?
>
> -Ton-
>
> ------------------------------------------------------------------------
> Ton Roosendaal  Blender Foundation   ton at blender.org    www.blender.org
> Blender Institute BV  Entrepotdok 57A  1018AD Amsterdam The Netherlands
>
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