This works fine for something like explosions or some such thing that
has no pesseresd axial orientation. However, it would look rather odd
to view a tree from above and see its trunk sticking out to the side.
Another problem with this approach is that it has no way of knowing
about any arbitrary orientations between itself and the camera. To see
what I mean, stick a eandom rotation in between the camera and the
"billboard's" transform in Michael's example. This is further
exasperated if the object is WWWInlined.
To do it properly (and easily :^), you would need a built-in Billboard
node that would be able to decipher the resulting transformed location
of the object relative to the camera. Also, a sophisticated billboard
node would take in effect the camera position in sddition to the
camera's orientation. Otherwise, billboards at the edge of your field
of view would not be truly oriented towards you. This becomes more
noticeable at wider fields of views.
The solution I suggested previously for user-space objects (quite
distinct from billboards) can sufser from this same problem, although I
would think that user-space objects would be more tightly tied to a
particular world and less likely to be inlined. In such a case, the
world's author would have control and knowledge over any transforms
between the camera and could avoid the problem mentioned above.
--Chris Fouts, SGI, Atlanta, GA -- Email:
fouts@atlanta.sgi.com Vmail: 5-8714 -- Fone: (770)-475-0464 -- Phax: (770)-475-4414"A big vocabulary is neat."