Not using "nested Dynamics":
Manipulate[
ContourPlot[Sin[5 x] Cos[7 y], {x, y} \[Element] Rectangle[],
Epilog -> {AbsolutePointSize@12, Point[t {1, 1}]}
],
{t, 0, 1}
]
vs
Manipulate[
ContourPlot[Sin[5 x] Cos[7 y], {x, y} \[Element] Rectangle[],
Epilog -> {AbsolutePointSize@12, Point[Dynamic[t] {1, 1}]}
],
{t, 0, 1}
]
The second one is much smoother because the FrontEnd does not need to care about anything but t, when for the first case the whole ContourPlot is recalculated.
