[BUG]: Monitor_nD per cm2 “lowers dimensionality"

[willend]

Describe the bug
With a “PSD” made using Monitor_nD:

COMPONENT PSD = Monitor_nD(xwidth=0.1, yheight=0.1, options=“x bins=128 y bins=128”)
AT (0,0,0) RELATIVE somewhere

changing options string to

COMPONENT PSD = Monitor_nD(xwidth=0.1, yheight=0.1, options=“intensity pr cm2 x bins=128 y bins=128”)
AT (0,0,0) RELATIVE somewhere

measures intensity not against x and y - but one of these vars.

Will fill in more details later

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