Partial data is wrongly located

[matze]

I always wondered why I saw some weird artifacts on the surrounding box. Turns out it's data from the opposite side of the cube. Here's an example, the full (but slightly cut) volume on the left and the volume sliced towards one side on the right. Circled in red is the data and its origin:

[nicolaisi]

I'll look into this. Nice catch, I never seen this bug before.

[matze]

@raghavaro also merge this one.