problems with lighting of front/back faces
It seems we have a number of problems with front/back faces lighting:
- 'lighted back' does not seem to work at all
- on shock.inp dataset (UCD reader) 'flip sides' is working well on smooth rendering
- on shock.inp dataset (UCD reader) 'flip sides' is not working on flat rendering
- on default test field 'flip sides' works only once, next clicks have no effect