[Regression] Waterfalls in Vivec fall the wrong way

Waterfalls in Vivec fall up instead of down. http://i.imgur.com/O43iiHF.jpg

Tested with latest win64 nightly.

(RM-3203 from redmine: created on 2016-02-11 by Lars Söderberg, , closed on 2016-02-11 by scrawl .)