Fix up vine polygon locations so they look less weird.  (Though it wasn't that noticeable with the texture it was using, it was with frame 0 instead of 2, which I used to debug.)  Set the w coordinate to 1 in the vec4s used for branch vertices (in case it helps; it didn't because they got translated by a vec4, not by a translation matrix, but might as well make it right).  Make norm a vec3 instead of a vec4 for the final segment's Vertex.  Fix up use of sin and cos in the per-branch-segment per-ring-segment vertices; this looks weirder but is actually correct (see the comment).  Vines now hang from the real bottom of the branches.