Date: Mon, 12 Feb 2007 10:16:32 +0100 From: Alexander Leidinger <Alexander@Leidinger.net> To: Stephen Montgomery-Smith <stephen@math.missouri.edu> Cc: Daniel Eischen <deischen@freebsd.org>, "Eugene M. Kim" <freebsd.org@ab.ote.we.lv>, hackers@freebsd.org Subject: Re: sin()/cos()/tan() for kernel code? '_ 'a Message-ID: <20070212101632.qa3p4f5wkkoccsk0@webmail.leidinger.net> In-Reply-To: <20070211115815.O62469@math.missouri.edu> References: <45CED641.7020608@ab.ote.we.lv> <Pine.GSO.4.64.0702110941580.19880@sea.ntplx.net> <20070211110815.O62469@math.missouri.edu> <20070211115815.O62469@math.missouri.edu>
next in thread | previous in thread | raw e-mail | index | archive | help
Quoting Stephen Montgomery-Smith <stephen@math.missouri.edu> (from =20 Sun, 11 Feb 2007 12:00:12 -0600 (CST)): > > > On Sun, 11 Feb 2007, Stephen Montgomery-Smith wrote: > >> >> >> On Sun, 11 Feb 2007, Daniel Eischen wrote: >>> Can't you do this in userland? Teach moused? >> >> Since you will only need sin and cos evaluated to the nearest =20 >> degree, if that, I suggest a simple look up table. There is also =20 >> something called the CORDIC method, I think, but I suspect that the =20 >> look up table will be so much easier to program, and negligable =20 >> extra space overhead. >> >> Stephen > > And if you do need more accuracy than the nearest degree, the formulae > > sin(x+h) =3D sin(x) + h cos(x); > cos(x+h) =3D cos(x) - h sin(x) > > for small h (say |h| less than half a degree) should provide way more > accuracy than you should need. There's work underway which moves the hard work of the mouse drivers =20 from the kernel to moused. The kernel just has a simple hardware =20 interface there, and the real interpretion of all the stuff from the =20 mouse happens in the userland. See http://www.semicomplete.com/projects/newpsm/ for more. So maybe it would be better to implement this in moused right from the =20 beginning... Bye, Alexander. --=20 Love is never asking why? http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID =3D B0063FE7 http://www.FreeBSD.org netchild @ FreeBSD.org : PGP ID =3D 72077137
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20070212101632.qa3p4f5wkkoccsk0>