Re. fastf_t: We (mainly Muuss) originally came up with that
as a
compromise to better fit the very small platforms (PDP-11,
the original
host for MGED, being the most important example). On any
modern
desktop, laptop, or mainframe, fastf_t should be chosen to
be double.
There is an intrinsic problem using floating-point
representation for
what are treated as real numbers; this shows up in any
"naive" CSG
system (meaning one that does not explicitly try to solve
the issue)
when a traced ray coincides exactly with a "seam"
between two unioned
primitives. Unfortunately this occurs relatively commonly,
when the
target geometry and the interrogating grid are nicely
aligned with the
coordinate axes. I recall early on a shotline dead center
on a vehicle
managed to "miss" it by squeaking through such a
crack.
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