As part of the design aspect of looking at 3D art programs, I looked at Paint 3D on my computer. It came free with the Windows Creator update.
It’s much more than an expansion of their original drawing program, Microsoft Paint. There’s a ton of new and convenient features.

3D objects
-Pre-made ones in the program
-Online library you can download from
-Draw your own, and choose from hard or soft edges

Colouring them
-You select an object or the background, and it locks on
-So you can only draw on one or the other at a time, which makes it a lot easier to do cleanly
-Easy to turn object on all axis
-You can use all of the tools, even the default stickers, on the 3D objects

Other things
-There’s lighting effects, and you can choose the colour of the light and a place for it to be coming from
-There is an array of different brushes, which you can change the size and opacity of
-There is a colour pick tool, a colour wheel, hex code input, and RGB input, as well as default colours you can choose from
-All brushes can be changed to matte, gloss, dull metal, or polished metal finishes

It’s a really powerful and useful program. Actual layers would be nice, but that’s more working in two dimensions, so they aren’t really necessary here. It’s a lot of fun to use!