Transformations are Mathematically Unpredictable

Confirmed Issue #8558995 • Assigned to Rick J.


Jonathan S.
Aug 20, 2016
This issue is public.
Found in
  • Microsoft Edge
Found in build #
Reported by 6 people

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Steps to reproduce

See the reductions in A rotation of exactly 90deg causes an issue, while a rotation of 89.9999 does not.

Original Report:


1 attachment

Comments and activity

  • Duplicates on version:
    Microsoft Edge 38.14393.0.0
    Microsoft EdgeHTML 14.14393

  • Repro’d on:
    Microsoft Edge 39.14905.1000
    EdgeHTML 14.14905

  • Explanation of what the demo does: applies transforms in a transform chain one by one with the help of keyframe animations. Each of the two elements is first rotated around its y axis, one by -90deg and the other one by 90deg. Then they’re rotated around their x axes by the same angle. Finally, they’re translated by the same amount along their z axes.

    After a rotation of -90deg around its y axis, the first element faces right. After a negative rotation around its x axis, it leans forward (so to the right of the screen since that is what it’s facing now) a bit. This is what is expected to happen.

    After a rotation of 90deg around its y axis, the second element faces left. All good so far. After a negative rotation around its x axis, it should lean forward (so to the left of the screen since that is what it’s facing now) a bit. Except it leans back (to the right of the screen), parallel to the first element, as if it had been rotated around the x axis in the opposite direction.

    Note that the subsequent transform (the translate along the z axis) happens as if the coordinate system of the element is in the expected (correct) position after the first two rotations, even if the actual element isn’t visually in the correct position.

    Also note that changing the 90deg value for the first rotation (around the y axis) to 89deg or 91deg doesn’t give an incorrect result like the 90deg case does.

  • Microsoft Edge Team

    Changed Assigned To to “Ibrahim O.”

    Changed Assigned To to “Rick J.”

    Changed Status to “Confirmed”

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