Merge branch 'swoop' of https://github.com/embree/embree into swoop
inversing ring direction, step1
step2
step3, subdivpatch1 works
step3
step4
step5
step6
step7, general patch works
step8
step9
step10
step11
step12
step13
step14
Merge branch 'devel' into swoop
step15
step16
step17