Dev Series: How Thumb Penetration in VRM Animations Is Corrected and Smoothed

A developer working on a VRM animation pipeline from live-action video has published the fifth article in a technical series, focusing on correcting thumb-finger intersection issues. When the thumb penetrates the index finger during animation, simply pushing it away distorts the original gesture, so the correct fix repositions the thumb on top of the index finger at a defined 18mm clearance threshold. The correction amount, called a "gate," is smoothed over time using rank filters and a Gaussian blur to eliminate brief glitches and unnatural step-like movements. Five failed smoothing approaches were documented, including binary thresholding and applying the gate to the wrong pose, before a working solution was found. The series continues with a forthcoming article on fixing a skinning issue that causes the wrist to crease.