mohawk also follows body pitch when accelerating
ground surface is 20 meters across.  play on!
tune the distance attenuation to use log of base 2.5
Merge pull request #430 from birarda/master

tune the distance attenuation to be a little less dramatic
Merge pull request #426 from PhilipRosedale/master

big ground plane
made mouth conform to the head sphere
Merge remote-tracking branch 'upstream/master'