Mirror issues

[farshizzo]

There is a bug in the clip plane calculation, replace that section with the following code:

#Setup reflection clip plane
s = -viz.sign(viz.Vector(dir) * viz.Vector(pos))
plane = vizmat.Plane(pos=pos,normal=dir)
dist = plane.distance([0,0,0])
lens.clipPlane([-dir[0],-dir[1],-dir[2],s*dist+0.001])