If you've not heard of GitHub, it is a very popular online software repository service. You can store and share the code for a project and track changes that occur by creating versions and "branches" for production and test use. One of the most important features is "diffs": the ability to "see" changes in the code. Added lines are shown in green, while deletions are in red.
But it's just for software, correct?
Not so! GitHub supports STL format, meaning you can store and track versions of your 3D model. This week they announced a more advanced feature: Diffs for 3D models! STL files can be shown in 3D, but now you can overlay two versions of a model and be shown (in red and green no less) the differences between the two. Green is added "shape", while red has been taken away.
Even better, they provide a slider control where you can visually observe the transformation from one 3D version to another.
Other 3D model repositories do not have this feature, as far as we can tell. While it may not be important for simple models, as complexity increases and multiple versions, it's just as important to track your 3D model as you would software.
If you have a complex 3D model project worth sharing, you'd best consider GitHub as your repository.