Alexander Gavrilov
16eafdadf6
When the input vector gets close to -Y, y and theta becomes totally unreliable. It is thus necessary to compute the result in a different way based on x and z. The code already had a special case, but: - The threshold for using the special case was way too low. - The special case was not precise enough to extend the threshold. - The special case math had a sign error, resulting in a jump. This adds tests for the computation precision and fixes the issues by adjusting the threshold, and replacing the special case with one based on a quadratic Taylor expansion of sqrt instead of linear. Replacing the special case fixes the bug and results in a compatibility break, requiring versioning for the roll of affected bones. Differential Revision: https://developer.blender.org/D9551