Make heightfield code more robust (partially addresses GitHub issue #184).
Make heightfield code more robust (partially addresses GitHub issue #184).

POV-Ray/povray,eblanca/povray,eblanca/povray,LeForgeron/povray,POV-Ray/povray,wfpokorny/povray,BentSm/povray,LeForgeron/povray,c-lipka/povray,LeForgeron/povray,LeForgeron/povray,LeForgeron/povray,wfpokorny/povray,LeForgeron/povray,POV-Ray/povray,c-lipka/povray,POV-Ray/povray,LeForgeron/povray,eblanca/povray,wfpokorny/povray,c-lipka/povray,wfpokorny/povray,BentSm/povray,BentSm/povray,POV-Ray/povray,LeForgeron/povray,POV-Ray/povray,POV-Ray/povray,wfpokorny/povray,BentSm/povray,c-lipka/povray,wfpokorny/povray,wfpokorny/povray,eblanca/povray