If you create a 3d model that looks exactaly like a Harley Davidson, then you stick the Harley Davidson logo on it, there's a likelihood the consumer is going to think Harley Davidson made this. They don't have to mistake it for a machine and it doesn't have to be in direct competition with any of Harley Davidson's product line. It's this sort of confusion over source or implied endorsement that's at the heart of trademark violations.