Is this a problem when a model is not a watertight mesh?

ned_poreyra

Let's say the model consists of a hundred of cubes that intersect each other in various places. It's a single object, but it's not a watertight mesh. Is this a problem for engines like Unity or UE4? Or, is this considered a bad practice in AAA studios?

TheGabmeister

Not good. If we're talking about hundreds of cubes, overdraw will be an issue. 

Obscura

Generally speaking, no, they would be totally fine with it. But if lets say you are planning to texture this asset in a unique way, then you would get a lot of wasted uv space. Also, if you are doing normal mapping, baked from a highpoly version, the intersections CAN bake badly.

rollin

Why isn't this watertight if every cube is watertight? Or are the cubes open on the backside?

I wouldn't say this is a huge issue with modern engines. But if you want to be complete sure just run a test

ned_poreyra

rollin said:

Why isn't this watertight if every cube is watertight? Or are the cubes open on the backside?

The cubes themselves are watertight, but I just got an idea for kitbashing a model quickly using low-poly meshes, trim sheets and procedural generation (like a sci-fi buildings or a spaceship). So the polycount would be normal, textures too, but it would be very easy to create a lot of variation in minutes. The only downside is making it a single, watertight mesh would be rather tricky (and kind of pointless).

rollin

For example Mechwarrior Online is using a lot of not watertight, not connected meshes. This watertight thing is bit outdated in 2019 imo