Tweaks to heightfield conversion.
Merge branch 'master' of https://github.com/highfidelity/hifi into metavoxels
Merge branch 'master' of https://github.com/highfidelity/hifi into metavoxels
Added options to selectively toggle heightfield/dual contour surface
rendering.
Fix for clearing empty nodes.
More gradual improvements to heightfield voxelization.
Merge branch 'master' of https://github.com/highfidelity/hifi into metavoxels
Merge pull request #3657 from ey6es/metavoxels

Further incremental improvements to heightfield voxelization.