OptionalbackgroundScene background. Omit to leave three's default (today's unset/transparent look);
null is the same as omitting. A color paints a solid backdrop.
OptionalbedBuild-plate outline (wireframe box) color.
OptionaldirectionalKey directional light intensity.
OptionalgridBuild-plate grid line color.
OptionalhemisphereAmbient hemisphere light intensity.
OptionalmaterialExtrusion (tube) material preset. Lines-quality geometry is unlit and unaffected.
A partial, declarative theme. Every field is optional; unspecified fields fall back to DEFAULT_THEME (replace semantics — the object fully describes the desired state, so
setThemeresets omitted fields to their defaults).