When to modal something as one object or multiple objects?

ryanzec

So I am new to 3D modeling and something that I have noticed is there are times where I see things being modeled as one object and others multiple and curious as to the reason one might do it one way vs the other. I imagine certain use cases that might lend itself to one way or the other but I am curious as to what those factors might be, from a person with very limited experience it seems like:

• UV mapping would seem simpler for the multiple meshes approach as ideally multiple meshes would lead to those meshes being simpler in shape
• Seems like multiple meshes would allow for breaking up the texture easier (not sure if there is a benefit to that though)
• Seems like some animations would be better for multiple meshes (maybe more "mechanical" animations) and a single mesh being better for others (maybe more "organic" animations)

Outside of that not really sure, any other big things I might be missing?

My use case for 3D modeling is also a bit unorthodox as I intend to use it for mainly rendering 2D sprites for my game. My reason for experiment with using 3D modeling in this way is that I want to have very fluid animations from many directions (ideally I'd like to be able to do 16 directions if possible) and doing that by hand in pure 2D would seem like a ton of work comparing to just modeling it is 3D (not to mention, it I need to make a change, I don't have to change 100+ sprites but just the model and then re-render everything). 

Eric Chadwick

Depends on the subject matter. Did you have a specific object in mind?

Also depends on the rendering engine. For example, intersecting meshes can cause problems with baking light maps. They can also cause depth sorting or aliasing artifacts. An example and info: 
http://wiki.polycount.com/wiki/Normal_Map_Modeling#Contiguous_Meshes

For rendering, like you're doing for your sprites, it doesn't really matter. It's faster to do separate meshes, so I'd suggest sticking with that.

ryanzec

Yea, most if not all concerns that relate to importing assets into my game are of little concern since I won't be importing the 3D assets into my game, just the render2D sprites.