RESOLVED WONTFIX 135905
ios8 webgl shader compiler thinks that pow(negative_float, 2.0) is zero 
https://bugs.webkit.org/show_bug.cgi?id=135905
Summary ios8 webgl shader compiler thinks that pow(negative_float, 2.0) is zero
makc
Reported 2014-08-13 14:35:07 PDT
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
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makc
Comment 1 2014-08-13 14:38:25 PDT
I actually have a recording of how that demo looked prior to commit: https://www.youtube.com/watch?v=y5-VwWlFZqo
Gregg Tavares
Comment 2 2019-07-22 21:42:06 PDT
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.
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