update method
void
update()
Implementation
void update() {
final start = count;
final end = geometry.drawRange['count']!;
if ( start == end ) return;
positions.updateRange!['offset'] = start * 3;
positions.updateRange!['count'] = ( end - start ) * 3;
positions.needsUpdate = true;
normals.updateRange!['offset'] = start * 3;
normals.updateRange!['count'] = ( end - start ) * 3;
normals.needsUpdate = true;
colors.updateRange!['offset'] = start * 3;
colors.updateRange!['count'] = ( end - start ) * 3;
colors.needsUpdate = true;
count = geometry.drawRange['count']!;
}