When comparing Anima2D vs Spine, the Slant community recommends Spine for most people. In the question“What are the best 2D skeletal animation tools?” Spine is ranked 1st while Anima2D is ranked 4th. The most important reason people chose Spine is:
Spine provides integrated modules for 14 major engines including GameMaker Studio, Cocos2Dx, LOVE, MonoGame, Unity, XNA, Flash, HTML 5, libgdx, Corona, and more. Generic runtime libraries are also available for C, C++, Objective C, C#, JavaScript, Lua and ActionScript 3. Dozens of third party libraries support additional targets.
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Pros
Pro Purchased by unity
Everything you could want from a skeletal animation system, free and because purchased by unity promises to be native in future.
Pro Free
Pro Spring bones
Much like spring joints native to unity, you can set bones to have dynamic spring animations based on their parents.
Pro Integration libraries support most engines
Spine provides integrated modules for 14 major engines including GameMaker Studio, Cocos2Dx, LOVE, MonoGame, Unity, XNA, Flash, HTML 5, libgdx, Corona, and more. Generic runtime libraries are also available for C, C++, Objective C, C#, JavaScript, Lua and ActionScript 3. Dozens of third party libraries support additional targets.
Pro Simplified UI allows for an easy learning curve
No-nonsense workflow allows you to create your artwork in programs much better suited for the task like Illustrator and Inkscape for example, while Spine itself focuses only on the important task of skeletal animation.
Pro Allows for easy use of artwork from third party programs
Spine's developers provide scripts which makes exporting artwork from third party programs much easier to do.
Pro Community-driven feature roadmap
Esoteric Software maintains public Waffle issue trackers to help plan and prioritize feature additions.
Pro Funded via Kickstarter
Spine received resounding support from Kickstarter backers, beating its pledge goal by over 5 times. A second successful Kickstarter added meshes and other important features.
Pro Price high for this product
Cons
Con No longer supported by Unity.
This has been merged into the 2D Animation package.
Con Uses the Unity hierarchy
It's impossible to rename your asset after making your animation, otherwise you lose dependencies.
Con Spine Professional is expensive
Spine Essential includes nearly all features, except IK, weights, and meshes. Spine Professional is expensive, though it does give all future updates for life (Spine is updated very often).
Con Requires EVERY developer to have a license
Ever developer needs a license, not just the animator, or an overall license for the project. The license agreement is extremely restrictive.
Con Doesn't support gamemaker 2.3
Con No integration for lesser known engines
Spine does not directly support some game engines, such as Construct 2 or Clickteam Fusion.