New coordinate calculations for head penumbra filter

Corrects issues with coordinate system calculations for the head penumbra filter.    Head penumbra filter now works with multiple positional streams.   Filter initial cutoff frequency lowered to exaggerate the effect (will be tuned further over time).
Yes, HALF_POWER^2 = QUARTER_POWER.   I commented out the first term, because I'm still tuning the gain ranges, and QUARTER_POWER seemed too extreme during testing.   That comment is simply a notation for me to pick a higher low-gain range - meant to be temporary.