QEF Implementation returns unexpected results on the Z value

Question

I have a QEF implementation like this

float atA[3][3] = { 0 };
FVector atb = FVector::ZeroVector;
for (const FEdgeIntersection& e : IntersectionList)
{
 const FVector& n = e.Normal;
 float b_i = FVector::DotProduct(n, e.Position);
 atA[0][0] += n.X * n.X;
 atA[0][1] += n.X * n.Y;
 atA[0][2] += n.X * n.Z;
 atA[1][0] += n.Y * n.X;
 atA[1][1] += n.Y * n.Y;
 atA[1][2] += n.Y * n.Z;
 atA[2][0] += n.Z * n.X;
 atA[2][1] += n.Z * n.Y;
 atA[2][2] += n.Z * n.Z;
 atb.X += n.X * b_i;
 atb.Y += n.Y * b_i;
 atb.Z += n.Z * b_i;
}
FMatrix M(
 FPlane(atA[0][0], atA[0][1], atA[0][2], 0),
 FPlane(atA[1][0], atA[1][1], atA[1][2], 0),
 FPlane(atA[2][0], atA[2][1], atA[2][2], 0),
 FPlane(0, 0, 0, 1)
);
FVector Result = M.InverseFast().TransformVector(atb);

When I have IntersectionList with these values

{Position={X=-960.00006103515625 Y=766.10652868112652 Z=-24.615383148193359} Normal={X=0.97101487888310145 Y=0.0000000000000000 Z=0.23901904733229035} }
{Position={X=-1006.2012716118422 Y=812.30773925781250 Z=-24.615383148193359} Normal={X=0.69663297076236907 Y=0.69663297076236907 Z=0.17147888527043917} }
{Position={X=-960.00006103515625 Y=812.30773925781250 Z=-65.753435217289166} Normal={X=0.0000000000000000 Y=0.97101488224128463 Z=0.23901903368967076} }

I get the following Result: {X=-996.07524496255644 Y=766.10633524904335 Z=121.94025333520403}

Now looking at it the Z is too far from where it should be from -24/-65 to a 121!!!

I expect it to be within close range of the value I inputted

Any idea What is wrong with my calculation!!

Thanks in advance

• Pepijn Kramer: I think the main issue is you're using unstable math. InverseFast makes some assumptions on input, so can you try Inverse? Then are your normals actually normalized (to length 1.0)? Or maybe this.
• ma1169: First, Thanks for responding. 1 - Using Inverse() doesnt change the result {X=-996.07524496255644 Y=766.10633524904335 Z=121.94025333520403} 2- Normals are normalized of course and I already posted the normals right next to the position, if you scroll the position, you will see the normal corresponding to the position