As soon as a model has big overhangs it's necessary to add a support structure to insure these parts of the model won't be printed "in the air" which would lead to a failed print.

Most of the slicers I know, and among them Kisslicer which is my prefered one, have the ability to automatically detect overhangs (based on a user angle value) and generate an appropriate support structure.
But still I know some other slicers that don't... For example the slicer that comes with the MiiCraft doesn't have that feature and most people that use this printer don't really know how to do it except by hand (add the support by hand in a 3D modeler). But this is not an easy task...

So I thought it would be nice to have a "3D support generator" that would do this automatically.
And I found out that the new MeshMixer release has such a feature.
Nice !

Preparation step

Before you import your mesh in MeshMixer, make sure it's orientated the way you want to print it having in mind that in MeshMixer the Up axis is Y.
Also make sure to scale it at the size you want to print it.
Rotating and scaling operations can be performed in MeshMixer but I found it easier to do it before import.

First step

After you imported your model in MeshMixer it will appear like this :

Imported mesh in MeshMixer

If it's not orientated the way you plan to print it, either you didn't do the "Preparation step" above, either you missed something.
But you can still rotate it and scale it now.

The first thing to do is to ask MeshMixer to detect the overhangs in the model that respect your criteria :

The overhangs are displayed in blue

Second step

The second thing is to ask MeshMixer to generate a support structure that fill follow your criteria.
You have a few sliders to define those criteria and you can just play with them to see how they act.
Generating the support structure based on your criteria is then just a one button click : "Support All Overhangs".
The support structure is then generated and displayed :

Auto generated support structure

If you're not satisfied with the generated structure you can remove it by clicking the "Remove All Supports" button, tweak the support criteria (sliders) to your need and simply generate the new corresponding structure again.
But you can also manually add a support by left clicking on the model and/or the generated structure, and/or remove a support by simply left clicking on it while holding down the CTRL key.

Third step

When you're satisfied with your support structure you can export your model back in STL format for 3D printing :

Model + support structure viewed in Meshlab

Voilà !
It's as easy as that...

Conclusion

If your slicer doesn't have a support feature you can now use MeshMixer to generate it.
It's easy and intuitive to use.

Simply keep in mind that

• the Up axis is Y
• left click will add a support
• Ctrl + left click will remove a support

I think it's a good feature but instead of having to delete the structure and tweak the sliders to create a new one, I would prefer to be able to tweak the sliders and see my support structure changing in real-time accordingly.
Am I asking for too much ?

For more information you can watch this good video tutorial.

Cheers !