On Fri, Oct 10, 2014 at 12:22 PM, Timothy Arceri <t_arc...@yahoo.com.au> wrote: > On Mon, 2014-10-06 at 17:03 +0200, Erik Faye-Lund wrote: >> On Fri, Sep 26, 2014 at 6:11 PM, Erik Faye-Lund <kusmab...@gmail.com> wrote: >> > Our current atan()-approximation is pretty inaccurate at 1.0, so >> > let's try to improve the situation by doing a direct approximation >> > without going through atan. >> > >> > This new implementation uses an 11th degree polynomial to approximate >> > atan in the [-1..1] range, and the following identitiy to reduce the >> > entire range to [-1..1]: >> > >> > atan(x) = 0.5 * pi * sign(x) - atan(1.0 / x) >> > >> > This range-reduction idea is taken from the paper "Fast computation >> > of Arctangent Functions for Embedded Applications: A Comparative >> > Analysis" (Ukil et al. 2011). >> > >> > The polynomial that approximates atan(x) is: >> > >> > x * 0.9999793128310355 - x^3 * 0.3326756418091246 + >> > x^5 * 0.1938924977115610 - x^7 * 0.1173503194786851 + >> > x^9 * 0.0536813784310406 - x^11 * 0.0121323213173444 >> > >> > This polynomial was found with the following GNU Octave script: >> > >> > x = linspace(0, 1); >> > y = atan(x); >> > n = [1, 3, 5, 7, 9, 11]; >> > format long; >> > polyfitc(x, y, n) >> > >> > The polyfitc function is not built-in, but too long to include here. >> > It can be downloaded from the following URL: >> > >> > http://www.mathworks.com/matlabcentral/fileexchange/47851-constraint-polynomial-fit/content/polyfitc.m >> > >> > This fixes the following piglit test: >> > shaders/glsl-const-folding-01 >> > >> > Signed-off-by: Erik Faye-Lund <kusmab...@gmail.com> >> > Reviewed-by: Ian Romanick <ian.d.roman...@intel.com> >> >> Ping? > > Are you just looking for someone to commit this?
Either that, or a reason for it to not be applied ;) _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
