> Date: Fri, 15 Nov 2002 00:08:09 +0100
> From: Artur Biesiadowski <[EMAIL PROTECTED]>
>
> Emanuel Brzostowski wrote:
>
> > I would appreciate if you could have a look at this bug and try to
> > point me to a solution or workaround, i have no more ideas how to
> > tackle this.
>
> I'm not sure if I understand your problem correctly, but it seems to
> be float precision error. It is not important that you use doubles -
> java3d will still convert them to floats internally (I also do not
> think that any of cheap GPUs out there support double precision - but
> I may be mistaken).
Chapter 4 of the Java 3D Specification is apropos, especially section 4.5
"High-Resolution Coordinates":
If one ventures even a hundred miles away from the (0.0, 0.0, 0.0)
origin using only single-precision floating-point coordinates,
representable points become quite quantized, to at very best a third
of an inch (and much more coarsely than that in practice).
Also in section 4.5.3 "Details of High-Resolution Coordinates":
Semantics of widely moving objects. Most fixed and nearly-fixed
objects stay attached to the same high-resolution Locale. Objects
that make wide changes in position or scale may periodically need to
be reparented to a more appropriate high-resolution Locale. If no
appropriate high-resolution Locale exists, the application may need
to create a new one.
Semantics of viewing. The ViewPlatform object and the associated
nodes in its hierarchy are very often widely moving
objects. Applications will typically attach the view platform to the
most appropriate high-resolution Locale. For display, all objects
will first have their positions translated by the difference between
the location of their high-resolution Locale and the view platform's
high-resolution Locale. (In the common case of the Locales being the
same, no translation is necessary.)
-- Mark Hood
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