Re: Venturi3d example
I do not get the idea behind it.
I had a brief look on the IndicatorLayer3D implementation and it returns true for a given lattice point, if this point is inside a layer. The latter is defined by an indicator passed by the constructor to IndicatorLayer3D.
If you want a Layer around an indicator, then pass your what-ever-indicator to the constructor of the IndicatorLayer3D. Saying that, first construct your indicators via +,-,* and then use IndicatorLayer3D.