in src/behavior.ts [100:117]
public renderSelection(hasSelection: boolean): void {
const {
selection,
interactivityService,
} = this.options;
const hasHighlights: boolean = interactivityService.hasSelection();
selection.style("opacity", (dataPoint: HierarchyRectangularNode<SunburstDataPoint>) => {
const { selected, highlight } = dataPoint.data;
return getFillOpacity(
selected,
highlight,
!highlight && hasSelection,
!selected && hasHighlights
);
});
}