Momenta
A straight propeller filmed one row at a time, so its blades come out as petals, until the shutter reads every row at once and they straighten.
The blades are straight. Time bent them.
A three-bladed propeller filmed by a rolling shutter. The sensor reads the frame one row at a time, top to bottom, so each row is a picture of a different moment, and the propeller turns more than once and a half while the whole frame is read. What comes out is a boomerang wrapped round the hub and two petals floating free of it. Nothing in the frame looks like a propeller.
Halfway through the loop the readout time shrinks to zero. The shutter becomes global, every row sees the same instant, and the petals straighten into three plain blades. Then they bend back.
The propeller really turns about twenty times a second. Its speed is chosen so that between two frames it turns a whole number of blades plus a sliver, which is why it appears to drift slowly round, one blade in fifteen seconds, and why the loop closes exactly.
Rendered offline from a single closed-form shader by the same module code a live page would run. No camera, and nothing leaves the machine.