The Ugly Swans is a 2006 Russian science fiction film based on a Strugatsky novel. It's directed by Konstantin Lopushansky. I'm glad I found this film. I understand the comparisons to Stalker, which also deeply impressed me.
It can be watched online, though the subtitles are difficult to make out:
Гадкие лебеди (Ugly Swans) 
Variety says some good things but concludes that "only fest auds will appreciate the baffling beauty of "Swans.""