shadowSoftness property
Controls the blurriness of the shadow. Set to 0 for hard shadows. Softness should not be changed every frame as it incurs a performance cost. Softer shadows render faster.
Defaultes to 1. Should be any any value between 0 and 1.
<model-viewer>
official document: https://modelviewer.dev/docs/#entrydocs-lightingandenv-attributes-shadowSoftness
Implementation
final num? shadowSoftness;