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This is the PP2014 MT5 (with Atan_Approximation …

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This is the PP2014 MT5 (with Atan_Approximation compound node) posted here https://forum.smithmicro.com/topic/1918/pp2014-material-room-math_functions-nodes-no-atan-asin-acos/29 for anybody who wants to play.

There's at least one known error, think of that as a free bonus! (I am trying to work out how to fix it). It returns +PI/2 instead of -PI/2 if 'Signed_Opposite' is negative and 'Signed_Adjacent' is zero. The horizontal white/grey line on the left of Math_Functions_27 shows that.

MT5 (and PNG icon) in the ZIP in the following subfolder:

Runtime\Libraries\Materials\3DCheapskate\Generic\Test

That's all.

The atan(X) approximation is as found here http://nghiaho.com/?p=997

atan(X) ≈ (π/4 * X) - (X * (abs(X)-1) * (0.2447 + (0.0663 * abs(X))))

Valid for X between -1 and +1 and returns angles in the range -π/4 to +π/4 radians (-45° to +45°).  Max error seems to be just under 0.1° (compared to a spreadsheet atan() function)

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