135905 2014-08-13 14:35:07 -0700 ios8 webgl shader compiler thinks that pow(negative_float, 2.0) is zero 2019-07-22 21:42:06 -0700 1 1 1 Unclassified WebKit WebGL 528+ (Nightly build) iPhone / iPad Unspecified RESOLVED WONTFIX P2 Normal --- 1 makc.the.great webkit-unassigned ap dino gman makc.the.great oldest_to_newest 1028910 0 makc.the.great 2014-08-13 14:35:07 -0700 well maybe not compiler. Steps to Reproduce: create any shader with x * x and pow (x, 2.0) side by side, you will see a difference. Expected Results: x * x is always equal to pow (x, 2.0) Actual Results: pow (x, 2.0) is zero when x < 0 Version: ios 8.0 12A4345d Configuration: iPad 3 See this commit https://github.com/makc/makc.github.io/commit/4221dc9788d2f509caf6427571656681fb3ad442 And the demo that is fixed by it: http://makc.github.io/three.js/map2globe/demo.html 1028911 1 makc.the.great 2014-08-13 14:38:25 -0700 I actually have a recording of how that demo looked prior to commit: https://www.youtube.com/watch?v=y5-VwWlFZqo 1555002 2 gman 2019-07-22 21:42:06 -0700 pow(x < 0, ...) is undefined behavior according to the spec According to the OpenGL ES GLSL 1.0 spec https://www.khronos.org/files/opengles_shading_language.pdf Section 8.2 genType pow (genType x, genType y) Returns x raised to the y power, i.e., x ^ y Results are undefined if x < 0. Results are undefined if x = 0 and y <= 0.