Improve speed of USD voxel export #193

Job	Run time
initial_checks / Load tox environments	3s
initial_checks / codestyle (ubuntu-latest)	37s
deploy-examples	0s
tests / Load tox environments	4s
tests / py39-test-all (ubuntu-latest)	4m 21s
tests / py310-test-all (ubuntu-latest)	3m 50s
tests / py311-test-all (ubuntu-latest)	3m 27s
tests / py312-test-all (ubuntu-latest)	4m 5s
tests / py312-test-qt (ubuntu-latest)	3m 29s
tests / py312-test-jupyter (ubuntu-latest)	2m 56s
tests / py39-test-all (macos-12)	11m 45s
tests / py310-test-all (macos-latest)	7m 31s
tests / py311-test-all (macos-latest)	5m 41s
tests / py312-test-all (macos-latest)	8m 47s
tests / py312-test-qt (macos-latest)	5m 36s
tests / py39-test-all (windows-latest)	6m 56s
tests / py310-test-all (windows-latest)	7m 29s
tests / py311-test-all (windows-latest)	7m 22s
tests / py312-test-all (windows-latest)	7m 2s
tests / py312-test-qt (windows-latest)	5m 48s
tests / py312-test-jupyter (windows-latest)	6m 1s
	1h 42m 50s

Provide feedback