This tutorial will teach the method of modifying your meshes created with Paint 3D and importing it into Roblox properly.
Otherwise, if you want to learn decent modeling, go the Blender route. Because of that, Paint 3D is recommended if you both want a cartoony video game and don’t want to bother with complex 3D modeling. It would take you humongous skill, much more than Blender, to model something realistic like this in Paint 3D, much like to paint something realistic in Paint. There’s no way to bend, twist, and remove individual faces/vertexes, UV map, and any sort of cool 3D modeling technique like in Blender. However, much like how Paint is limited for painting digital art, Paint 3D is still limited for modeling 3D models. (Not taken by me, obtained from the Internet)
