A string geometry calculation problem has been solved

Hi all,

The suddenly disappeared rope when creating it was found due to a very interesting floating point number calculation issue in computers: the 'NaN', not a number value.

C# defines a valid value called float.NaN for float data type. Under some circumstances, a math calcualtion would get a NaN result,
e.g.,
The additions ∞ + (−∞), (−∞) + ∞ and equivalent subtractions
The square root of a negative number.

In our project, the calcualtion for the rotation angle, rotationAngle = -(float)Math.Acos(Vector3.Dot(rotationAxis, previousAxis)), sometimes returns a NaN as well, this is the root of the problem.

This bug has been fixed by doing---
    if (rotationAngle != rotationAngle)
        rotationMatrix = Matrix.Identity;
    else
        rotationMatrix = Matrix.CreateFromAxisAngle(rotationAxis, rotationAngle);

A new StringGeometry.cs file with the fix will be sent out soon.

Kindest regards,
Jun