Animation without rig

So, can one animate without a rig?

A friend has trouble visualizing with rigging…

I wonder if it is okay to simply visualize the maximum/minimum degree of movements and animate based on it?

You can. If you set keys directly on maya objects over time , it’ll animate.

The chance that you’ll be effective working like that, however, is very, very low. The number of keys you need to set to describe a even a very simple motion in nothing but direct translate or rotate keys is much, much larger - at least one and maybe two orders of magnitude larger.

The whole job of the rig is to tell the computer how to get from pose to pose so you can concentrate on the look of the poses and the timings. Rigs are the tech that do what you’re looking for. You may need to shop around for a better, more user-friendly rig (maybe people can chime in with free examples or youtubes that show good rigs) . But working without rigs isn’t a good idea – there’s a reason that nobody who animates for a living will do that voluntarily!

I may not be entirely following you, but you might want to look into morph target animation (also called vertex animation). In the case of morph target animation, modeled poses of a character are interpolated between in order to achieve the desired motion. Each pose is a separate mesh (or set of vertex positions). Often times bones/skinning (i.e., skeletal animation) is used to created the poses, but morph target animation can be created without the use of bones/skinning. You could alternatively explore skeletal animation sans skinning. In what I’ll call “skin-less” skeletal animation, the character is broken up into a series of likely hierarchically connected meshes that are all animated via said meshes’ own pivots. Many early 3D games depended on either morph target animation or “skin-less” skeletal animation (think Quake and Tomb Raider respectively). Even now, modern games commonly leverage morph target animation for facial animation.