\begin{acks}
	We thank the anonymous reviewers for their constructive comments.
	We are grateful to Jerome Spanier for many helpful suggestions.
	This work was supported in part by NSF grants 1717178, 1730147, 1816041, 1900849, and 1900927, an NVIDIA fellowship, the Ronald L. Graham Chair, and the UC San Diego Center for Visual Computing.
\end{acks}
