I borrowed a pivot point calculator. Basically, it's
R3 = R2 + RANGE (same as: PP + RANGE * 2)
R2 = PP + RANGE
R1 = (2 * PP) - LOW
PP = (HIGH + LOW + CLOSE) / 3
S1 = (2 * PP) - HIGH
S2 = PP - RANGE
S3 = S2 - RANGE (same as: PP - RANGE * 2)
However, it would be great if you could add pivot midpoints. These are apparently used when the range is higher than normal (tried to find this 'higher than normal' using google, but failed). Maybe you could make this optional ?
Also, from the attached spreadsheet, the weekly and monthly values are also used by traders. Apparently, confluence adds significance to pivots.
Finally, I've had a bit of a look around, and for futures the full day's range is used (i.e. take into account the overnight high or low).