Matrix4x4 Decompose failing

[ptasev]

I'm not sure if this is a bug (since I don't quite understand the math fully) and I was hoping someone here could tell me. I am creating an SRT matrix, and then inverting it. When I decompose the inverted version it fails. Is this behavior expected?

I am using dot net core 3.1.3. My CPU is AMD Ryzen 5 2600.

using System;
using System.Numerics;

namespace tmp
{
    class Program
    {
        static void Main(string[] args)
        {
            var pos = new Vector3(0.217761353f, 0.129548967f, 7.627072E-05f);
            var rot = new Quaternion(0.527541637f, 0.470849365f, 0.527542233f, -0.47085017f);
            var scale = new Vector3(0.7462687f, 0.480769f, 0.9999995f);

            // Create SRT matrix
            var transMat = Matrix4x4.CreateTranslation(pos);
            var rotMat = Matrix4x4.CreateFromQuaternion(rot);
            var scaleMat = Matrix4x4.CreateScale(scale);
            var regm = scaleMat * rotMat * transMat;

            var b = Matrix4x4.Decompose(regm, out Vector3 s, out Quaternion r, out Vector3 t);
            if (!b) throw new Exception("Bad decompose!");

            // Create inverse of the SRT matrix above
            Matrix4x4.Invert(transMat, out Matrix4x4 tmi);
            Matrix4x4.Invert(rotMat, out Matrix4x4 rmi);
            Matrix4x4.Invert(scaleMat, out Matrix4x4 smi);
            var invm = tmi * rmi * smi;

            b = Matrix4x4.Decompose(invm, out Vector3 si, out Quaternion ri, out Vector3 ti);
            if (!b) throw new Exception("Bad decompose!"); // Throws here
        }
    }
}

I'm starting to think this is due to floating point precision. I see the implementation of Decompose has an epsilon for the rotation matrix at the end that I'm failing to meet. I just don't understand how only the inverse is losing so much precision.

[ghost]

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