Re-Creating Modifiers in Geo-Nodes
The best would be to try to replicate the exiting Grease Pencil modifiers with Geometry Nodes. That would give a better view of what else may be needed, or should be considered.
I think this will also reveal some issues/limitations that the current modifiers have. Time Offset would be the modifier I am most inrested in seeing as a geo-node proposal, as this has many implications on how time works within this setup.
I am working on a public cut-out rigging addon for 3.6 LTS, this can show some of the complicated ways ‘time’ is used in Grease Pencils to control what is being shown, in some non-conventional ways. You can see a preview of that system here https://www.youtube.com/watch?v=sQ_ZPXVrPsQ
Grease Pencil Frames/Time
Grease Pencils should definetly have more explicit data elements to consider beyond what comes with curves. More performance is cool but to @HooglyBoogly’s point there are additional elements within grease pencils that are not part of curves. One big element in addition to layers is Frames/Time!
Within a grease pencil layer you can have several different frames, that all have explicitly different stroke data within. This I think will be a large topic for porting grease pencil into geo nodes. How does a user set what frame they are working with, edit different frames from the current frame (or maybe we can only input data on the scene’s current frame?), also consider the relativity of what frame has data vs what frame is being displayed. This idea has a lot of influence over how cut-out rigging could work.
Now cut-out rigging doesn’t explicitly require time, just keyframe instancing, but avoiding concept of frames will be a pain as a lot of workflows in the 2D are very time based. So I hope that we retain the ability to control frame/time property from a geo-node.
For a crazy example consider a user using simulation nodes to generate some mesh, like a rope moving around. Then inputting that simulation to generate grease pencil strokes ontop of this rope, which would be grease pencil strokes saved on different frames as a simulation plays!
Has anyone else considered how time/frames would work in this proposal?
Line Art Considerations
Considering New Line Art proposal 2023, feedback? from @ChengduLittleA proposal I would like to just remind that this workflow for line art would likely be heavily influenced by this proposal.
For my personal project https://www.youtube.com/tinymediatv I have been creating 3D buildings with Line Art outlines to give them 2D look. Currently it’s an all or nothing approach to processing geomoetry for Line Art. So in addition to having a way to create new grease pencil data, it would also be intresting to use Geo-Proximity or something similar to generate custom outlines with nodes, filter out parts of the geomoetry for line art, etc…