Could someone please help point out the area in the Babylon.js source code where a child node/mesh follows the position and rotation of its parent via matrix math?
I was looking into transformNode.ts, though I’m unsure if I’m on the right track.
Thank you for your help 
It would be great to explain what you’re trying to accomplish as there are many ways to go about it. You could simply attach a TransformNode like you say and let the engine do the maths. 
You’re right I’m curious about how to do this math manually
I’m working with a Physics world that’s separate from Babylon rendering and am interested in the creating a sticky spike grenade like in Halo, where the object sticks to and follows another object’s position/rotation
For the separate Physics world, I’d like to stay away from creating parent-child relationships for the object and spike grenade. Instead, I’d like to manually update the position/rotation of the spike grenade to follow the object
think we need to deal with the local quaternion problem.
Thank you for looking into this, @11128 Indeed, it looks close with a slight rotation issue
Your Playground reminds me of the post: How weapon is attached to a rigged animation - #3 by gbz
I think this place in the source is it or getting warm