Why is humanoid 3D model so deforming?

Humanoid 3D models deform unexpectedly mainly due to issues with rigging (skeleton setup), mesh topology, or weight painting. Rigging errors—like misplaced bones or unoptimized joints—make the model bend incorrectly. Poor topology (mesh without clean loops around high-movement areas like elbows/knees) causes stretching or tearing. Incorrect weight painting (uneven vertex influence) leads to unwanted movement, e.g., shoulders pulling the neck. To fix it, check rig joint alignment, refine topology around joints, and adjust weight painting to limit each bone’s influence—tools like Blender’s weight paint mode simplify this.