Assertion fail when applying transform on Mesh

[Guilherme Almeida]

I'm creating a mesh from a SCNNode's geometry. When trying to apply a transform, I get the following fatal error:

Euclid/Plane.swift:195: Assertion failed
2022-11-02 14:21:16.644227-0300 NKAR[77549:28776043] Euclid/Plane.swift:195: Assertion failed

This error is caused by a failed normalization assert on Plane.swift.

Minimally Reproducible Example:

extension SCNNode {
    func withTransform(scale: SCNMatrix4, registration: SCNMatrix4) -> SCNNode {
        guard let mesh = Mesh(self.geometry!) else {
            fatalError("Couldn't create Euclid Mesh from geometry")
        }
        
        let scaleTransform = Euclid.Transform(scale)
        let registrationTransform = Euclid.Transform(registration)
        
        let transformed = mesh
            //.smoothNormals(Angle(degrees: 20.0))
            .transformed(by: registrationTransform)
            .transformed(by: scaleTransform)
        
        let geometry = SCNGeometry(transformed)
        
        return SCNNode(geometry: geometry)
    }
}

I'm loading the file using ModelIO. Mesh file used: https://1drv.ms/u/s!ApWujpauQd0YgpBiWTsh1zxIN-pWsA?e=4VEFP2

[Nick Lockwood]

@naccib thanks for reporting this. What are the values you are using for scale and registration in your example?

[Guilherme Almeida]

scale is a simple symmetric scaling matrix with a factor of 0.001 (so 0.001 on the $m_{11}$, $m_{22}$ and $m_{33}$). The registration matrix is a little bit more complex because it's different at each runtime, but it only contains a rotation and a translation.

I've found that simply deleting this assertion fixes the issue with no apparent difference from applying those two transforms with SceneKit.

[Nick Lockwood]

I'm not able to reproduce the assertion with the parameters you've given, so I suspect the specific transform matrix might be relevant. I'd prefer not to delete the assertion until I can understand why it's firing.

[Guilherme Almeida]

That's a reasonable approach. This causes the assertion to fire:

Scale Matrix (scale):

SCNMatrix4(m11: 0.001, m12: 0.0, m13: 0.0, m14: 0.0, m21: 0.0, m22: 0.001, m23: 0.0, m24: 0.0, m31: 0.0, m32: 0.0, m33: 0.001, m34: 0.0, m41: 0.0, m42: 0.0, m43: 0.0, m44: 1.0)

Registration matrix (registration):

SCNMatrix4(m11: 0.9978629, m12: -0.06377151, m13: -0.014242808, m14: 23.246614, m21: 0.018626042, m22: 0.068675354, m23: 0.9974652, m24: -149.8618, m31: -0.062631726, m32: -0.99559873, m33: 0.0697164, m34: -112.913246, m41: 0.0, m42: 0.0, m43: 0.0, m44: 1.0)

[Nick Lockwood]

@naccib this is now fixed in 0.6.1