Dragging the scroll bar slows performance

[puppybits]

Dragging the scroll bar causes tons of slowdown. When there are 1 million models (I know this is an unrealistic metric) it really chugs. Need to use some faster algorithms when scrolling. Normal use cases (under 10,000 models) won't see any major issue. The complexity of this an unlikeliness of a real-world app needing this causes it to be on the back burner.