HI Allen,
Allen Bierbaum wrote:
> It seems like we would need to use the doubles path everywhere. Said
> another way, why would camera calculations be the only place that this
> is needed. Wouldn't we also need it with the bounding volumes in
> general since the verts in the geom cores are going to be doubles. It
> seems like if we used floats for the bounding volumes in this case, then
> things like ray intersection detection would be broken.
Everybody I've seen so far doesn't do that. They all use tiles that are
centered
around the origin and use float data. That makes sense, as floating point
numbers loose precision rapidly when you move away from the origin, so even
with
doubles you can represent very large numbers, but once you get far away from
the
origin precision gets lost. Then those tiles are positioned in space using a
transformation (possibly double precision, but not necessarily, see below). So
in theory you would have to do everything related to transformations (including
bvolumes) with double precision.
I have been confronted with something like a flight simulator before, and in
that application we got away only doing the camera math in double and
everything
else in float. IMHO the reason was that there are inversions and other matrix
math in the Camera calculations that get bad for large numbers in float. That's
why I recommended that as a first step, and try to write it in a way that would
make it easy to expand later.
> Has anyone successfully used OpenSG with double precision?
I've never needed it so far.
Dirk
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