From: Paul Berry Date: Wed, 27 Jul 2011 22:53:31 +0000 (-0700) Subject: glsl: improve the accuracy of the atan(x,y) builtin function. X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b1b4ea0b3679db0b8fddaa9663a10d4712bba3b7;p=mesa.git glsl: improve the accuracy of the atan(x,y) builtin function. The previous formula for atan(x,y) returned a value of +/- pi whenever |x|<0.0001, and used a formula based on atan(y/x) otherwise. This broke in cases where both x and y were small (e.g. atan(1e-5, 1e-5)). This patch modifies the formula so that it returns a value of +/- pi whenever |x|<1e-8*|y|, and uses the formula based on atan(y/x) otherwise. --- diff --git a/src/glsl/builtins/ir/atan b/src/glsl/builtins/ir/atan index cfecc1f1749..7b5ea13c6ba 100644 --- a/src/glsl/builtins/ir/atan +++ b/src/glsl/builtins/ir/atan @@ -54,7 +54,9 @@ ) ( (declare () float r) - (if (expression bool > (expression float abs (var_ref x)) (constant float (0.000100))) ( + (if (expression bool > + (expression float abs (var_ref x)) + (expression float * (constant float (1.0e-8)) (expression float abs (var_ref y)))) ( (assign (x) (var_ref r) (call atan ((expression float / (var_ref y) (var_ref x))))) (if (expression bool < (var_ref x) (constant float (0.000000)) ) ( (if (expression bool >= (var_ref y) (constant float (0.000000)) )