Continuous ray visibility for positioning a detector/lens

[alpo-kuusisto]

When building a bit more complex scene it takes some time for all rays to be redrawn. If moving e.g. a detector to place it precisely into focal plane, all the rays are cleared after minute move and user needs to wait redraw to see if placement was correct (and probably do few more move/waits). I end up often dragging a ruler into focal plane, since that does not force redraw, and then place the detector along the ruler.
Could the 'old rays' remain visible for easier drag-positioning of elements? Perhaps they could be grayed out to indicate ongoing redraw.

[ricktu288]

Now you can enable Settings -> Show simulator controls and then turn off "Auto Refresh". Then when you drag some optical element, the old rays will remain visible until you click "Refresh Simulation".