some tiny speed improvements for indexed vertex array
some tiny speed improvements for indexed vertex array

yuhangwang/pv,yuhangwang/pv,yuhangwang/pv,biasmv/pv,biasmv/pv,biasmv/pv,Traksewt/pv,Traksewt/pv,CyrusBiotechnology/pv,Traksewt/pv,CyrusBiotechnology/pv,CyrusBiotechnology/pv,yuhangwang/pv,biasmv/pv,CyrusBiotechnology/pv,Traksewt/pv