My name's Tomasz. I'm making a crowdfunded 2D animation called Sex and Taxes. I'm using Blender to make it. There's lots to recommend Blender for 2D work, for instance it's great to have access to a full 3D system when you need it, as well as the node-based shader editor and compositor. 2D animation in Blender is facilitated by the Grease Pencil system which is relatively new, but being improved quickly. For me the advantages of this environment outweigh the difficulties, for others it might work out the other way.
I'm writing this post to help animators make an informed choice about whether to invest in learning Blender's ins and outs for their project. I also hope this will be valuable feedback for the Grease Pencil team about what the biggest pain points currently are for me.
Switching between tools is slow
Switch between Grease Pencil tools instantly (without having to manually change mode)
I'm starting with this one because think its likely the biggest potential deal-breaker for artists on a deadline. Grease pencil has tools for drawing and editing drawings. These are spread over several modes. The modes I use the most often are called Draw, Sculpt and Edit. Blender has an extensive shortcut mapping system, but there's currently no way to switch to a Grease Pencil tool in a mode you're not currently in with a single keystroke. For instance: I'm in drawing mode, drawing a line. I want to smooth that line. I can't switch to the Smooth tool with a single keystroke because the Smooth tool is part of the Sculpt mode (and shortcuts don't natively allow a combination of switching modes and then specifying a tool in that mode).
The best I can do at the moment is press Q to get to the 'Quick Favourites' menu, then click 'Sculpt' to enter the correct mode there, then press Q again and click 'Smooth'.
Not only is this a four-step process, I can't train my muscle memory to carry it out quickly because I'm required to look at the screen and click the correct buttons. These little moments of friction add up quickly when they're part of an operation so fundamental to creating artwork.
Edit: Falk David points out that using the pie menus is a faster way to change between modes.
My proposal for improving speed of tool switching can be found here.
Messy, blobby corners on line art
Creating pin sharp corners in finished line work isn't currently possible. When you need a line to change direction, the side of the corner with the wider angle will be rounded. This can be a serious problem if you want thick, sharp-cornered line art in your work. Think of Genndy Tartakowsky's animated Clone Wars series for instance.
For comparison, here's how vector line cutting is handled in Clip Studio Paint vs Blender. CSP doesn't get it right all the time (see the lower right corner of the rhombus), but the corners it creates are usually sharp and neat enough even at thick line widths.
I have a proposal for how Grease Pencil's cutter tool could be modified to create much sharper looking corners here. Vote it up if this is important to you too!
Making the handling of corners worse, the Cutter tool (used to trim stroke segments based on intersections with other strokes) doesn't accurately cut strokes at intersections. Again this will be more of an issue the thicker your linework is. Below I've tried to trim the intersecting line segments to create a Z-like shape. The misaligned cuts are clearly visible.
Stroke width doesn't behave correctly at the start of a line
For some visual styles this won't be an issue but if you want to use bold, variable thickness lines, this can slow you down considerably.
Currently, on windows, when you use a Cintiq to draw, and you have pressure mapped to line thickness, the start of your line will often be tapered in a way you don't want.
From conversations with developers I understand that the drawing system isn't correctly passing through pressure changes when the stylus is stationary on the drawing surface. The moment the stylus first touches the surface a touch event with pressure is registered, but as the tip comes to full rest and more pressure is applied, that extra pressure isn't reflected in the start of the stroke. Which means the start of the stroke usually ends up being much thinner than it should be, giving an unwanted spike.
Support for looping and reusing drawings on the timeline is limited
Grease Pencil doesn't currently have a top-level concept of drawings that can be edited in one place, but displayed at multiple places on the timeline, although this effect can be simulated using modifiers.
One place this causes problems is when dealing with sequences that should loop. Consider this animation:
I've created the repeating jump by first animating a single jump, then copy/pasting those keyframes and shifting the position of those drawings to the right for the last last three jumps.
If I decided that some of the drawings need refining I'd have to edit the drawing, then copy/paste that keyframe into the five other locations on the timeline, and again shift the last three over to the right.
What's missing is a flexible way to edit any of the frames of the first jump we animated and have that change automatically propagate to the other instances of the jump without us needing to do any extra work.
Blender has a Time Offset modifier that can be used to make loops but this has severe limitations: a loop created this way repeats continuously over the entire timeline. You can't use it to loop a sequence of frames just a few times, while preserving the drawings you've placed before and after the looping section.
I'd like to help
If you're a developer reading this and would like me to review any new work addressing the things I've mentioned I'd be happy to do it. I've successfully built Blender from source before so I hope not to need too much hand-holding to negotiate the process.
Here I've mentioned the biggest hurdles I'm experiencing, I've posted more issues and suggestions at https://blender.community/u/tomasz.brain