Addde volume example
passthrough model material
Merge branch 'release/v0.4.0'
Merge branch 'release/v0.4.1'
Merge branch 'release/v0.5.0'
Merge branch 'release/v0.5.1'
Change to absolute database keys.
Merge branch 'master' into develop
Fixed issues of simple example after accidental merge with volume branch.