FIXMATH_FAST_SIN gives rounding error #24
Description
I've found a bug with your fast implementation of sin() (FIXMATH_FAST_SIN),
this bug doesn't happen with the more accurate version.
I made an animation of a rotating cube but noticed it would shudder, i tracked
it down to the sin function providing very poor accuracy as the return value
from it reached and passed 0.
I'm running it in Visual Studio 2009 and tracking the values in the debugger so
the values i see are the 32bit number representation of the fix16_t variable
but they go like this...
1842, 899, -74, -1055, -2037, -2990, -3979, all good so far, then suddenly it
jumps back to positive with 4782, 3790, 2803, ... it then continues down
through to -65536 (-1.0) as it should do.
Original issue reported on code.google.com by [email protected] on 21 Apr 2013 at 12:58