[Bf-committers] About design on grease pencil object

[Joshua Leung]

Hi Antonio,

First, I agree that it's a good idea to be moving towards haivng a
dedicated "Grease Pencil Object" type. For "full hand-drawn animation" in
3D, that is useful and necessary. The biggest benefits are:
i) *We can have a dedicated "Draw Mode"* - Instead of having to hold down
any modifier keys, clicking/tapping with a mouse or pen will just draw
(i.e. think "Sculpt Mode", "Texture Paint Mode", etc.). For artists doing a
lot of dedicated drawing, that is a HUGE productivity boost (and more
ergonomic). Plus, we don't need to worry about things like adding ways to
disable/remap the 3D cursor positioning, to avoid accidentally moving it
and runing drawings.
ii) *Easier Instancing of Drawings* - With a Grease Pencil object, we can
use all the well-established techniques for duplicating and repeating
objects in different places (e.g. duplicate/link duplicate objects,
dupliverts, particles?, etc.).  As Mattias demonstrated the other day, this
is useful for things ranging from having an army of hand-drawn warriors
marching around, to placing trees and foliage on a hillside.
iii) *More Natural Handling of Parenting/Transforms* - With the layering
parenting, it's become a bit of a mess with transforms having to be
calculated, applied/unapplied per layer in many places, to replicate
functionality that's available with Objects + Object Data naturally for all
the other geometry types.
iv) *Use of the Object System to Manage Data* - Finally, we can take
advantage of the object system to manage characters vs props vs
backgrounds, instead of trying to use the GP layers to take care of all of
it. Maybe if they could be hierarchical instead (i.e. a big can of worms;
for starters, the list widgets would be need to become trees :) the layers
might still work, but it's simpler just to rely on some existing mechanisms
instead of adding more complexity.
v) *A natural approach for *"*Drawing Planes"*?

All this is fine and good. It's a natural evolutionary step towards
integrating this type of asset (i.e. hand-drawn animated assets) into 3D
scenes as a first-class citizen. :)

------------

However, I'm still very much on the fence about whether we should abandon
Scene-level annotations. You're right that in terms of mental models,
keeping it around *might* (and that's a big might) be one to many
conceptual hurdles for people to get their heads around. That said, I'm
currently not convinced yet that removing it is 1) necessary, 2)
beneficial, and 3) the best course of action.

It's somewhat ironic that we're talking about going from having
Scene-anchored GP to object-anchored GP *again*, as just 2-3 years ago, we
were making the opposite switch after years of using object-anchored GP
since the early 2.5 days ;). Sure, last time we also had the additional
problem of only showing the GP data attached to the active object being
visible. However, I think some of the arguments we made last time still
hold about scene-anchored being simpler to manage (for some use cases).

*Pros of Keeping Scene GP*:
1) *Scene GP works better for the Annotation/Drafting Workflow*s - Right
now, it is possible to use Grease Pencil to annotate the workspace while in
any mode, with any object selected. With what you're proposing (i.e. with
no GP object set, if you hold down D and start drawing, it will create a GP
object in the scene and add your strokes to it), there are a few issues:
    a) What happens if you suddenly add an extra GP object to the scene?
Which one of the two will it add strokes to if the active object is not a
GP object?
    b) If you decide which datablock should recieve the strokes based on
the name of the datablock, IMO, it's really not that great to have
hardcoded hidden/implicit conventions in places to make things work. (It
was one of the issues I had with some of the stride follow stuff)
    c) This breaks the UI principle that you're always operating on data
from the active OR selected object(s) only. For example, when you're in
editmode on a mesh, and want to add/remove annotations, it's fine when
Scene GP is used (i.e. not an object, scene/world-level stuff is getting
modified), but with Object-GP you end up editing an arbitrary object's data
while actively work on another.

2) *Less Workflow Overhead* - With Scene GP, you can keep everything
together in the same datablock until you figure out how you want/need to
partition the data to better manage it. In other words, creative freedom
and flexibility. With Scene GP present, you can still later decide to
assign your scene GP datablock to a GP object (much like you can change
which mesh datablock an object uses), and then carry on as if you'd started
that way from the beginning.

However, Object-GP gives off a different vibe - that of being a much
stricter/more structured way of working, where you're forced to figure out
up front how you want to manage your data.

3) *Continued Testing of Annotation Workflows* -  This point probably goes
both ways, but by keeping Scene GP around, it is more likely that stuff
that doesn't work well with non-object GP workflows (i.e .stuff that won't
work well in the other editors) is less likely to go unnoticed. Even now,
we already have that problem -- the workflow for colour palettes and brush
types stuff works pretty terribly for all the 2D editors, and is in many
ways overkill  (TBH, I'm increasingly thinking that for those places, we
should just roll back to using the old layer-bound color + thickness
options, though there are problems with doing that from a drawing-code
perspective).

4) *Sketched-Based Input for Tools/Addons* - For stuff like modelling tools
or posing tools which use sketched lines as input, again, it's not that
nice that we have to go around digging for some other object in the scene
that has the sketch data we need (and/or having that manage that object).
Keeping thing scene-level makes it easier to manage (i.e. you can just do a
"C.scene.grease_pencil" to get the data, if "C.active_gpencil_data" isn't
giving you want you need).


*Cons of Keeping Scene GP*:
1) *Potentially Confusing UI (Properties Editor vs View Properties Region)*
- With Object GP, the properties editor will show GP settings under one of
its tabs. This could get confusing when Scene GP setting still get shown
via the viewport properties region(s). The "obvious" fix is therefore to
simply get rid of Scene GP so that this conflict doesn't show up. Which is
probably how we got here :)

However, this ignores that all the other editors where GP annotations may
occur (e.g. Sequencer, Image/UV Edit, Masks/Tracking, Nodes, and soon
Animation Editors) will still need to have panels showing the options for
the GP datablock being used there for annotations. You're still going to
get a bit of that confusion happening in some cases. But, keeping Scene GP
just means that there is still a clear + consistent workflow for annotating
stuff across editors.

2) *Code/Keymap Overheads* - It means we have to keep one more codepath
viable and functioning. Given the trouble we have so far with no
clobbering/crippling the 2D editor GP workflows with 3D-art centric stuff,
maybe this is a legitimate concern :(


---------

Regards,
Joshua


On Fri, Apr 7, 2017 at 6:41 AM, <blendergit at gmail.com> wrote:

> Hi,
>
> As you probably know, we are working to implement new grease pencil object
> and the use of new draw manager and more new gp stuff.
>
> Recently, I uploaded a new branch “greasepencil-object” base on
> “blender2.8” branch to blender.org git server with the code we are
> working on.
>
> Daniel M. Lara (pepeland), Matias Mendiola and I have been thinking in a
> better workflow and we have found some topics that need a decision. I had
> some conversation on IRC about them, but I want to share them in the
> mailing list and get more feedback before take any action:
>
>
> 1) Currently, in 3D view you can create GP strokes at scene or object
> level. With the new grease pencil object, it not makes sense to have GP at
> scene level and we can remove it.
>
> To have GP at scene level only adds complexity to design and make more
> confuse the use of grease pencil for artists. There is only a concern about
> add-ons that are using grease pencil at scene level, but as Blender 2.8
> will require a review of current add-ons, we think this is not a big issue.
>
> Of course, the old files with grease pencil at scene level will be
> converted to new grease pencil object when they are opened in Blender 2.8.
>
> 2) Grease pencil has two uses, animation and annotations. Annotations in
> 3D can be supported by the automatic creation of a GP object (this is the
> approach of other 3D programs of the market). Besides, the use of GP object
> for annotations adds functionalities as hide, move, scale, rotate,
> organize, etc.
>
> For 2D annotations (Node Editor, VSE, etc.) we can keep a basic
> functionality, but we will not support new drawing features, only basic
> support to add notes.
>
> The availability to draw animations in different context is a source of
> misunderstanding for new users. We think to keep the animation workflow in
> the 3D viewport is the way to follow.
>
>
> We would like to hear your opinions and ideas.
>
>
> Best Regards,
> Antonio Vazquez (antonioya)
>
>
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