[vtk-developers] Speeding up raycasting on x86

[Volpe, Christopher R (Research)]

> -----Original Message-----
> From: Lisa Avila [mailto:lisa.avila at kitware.com]
> Sent: Thursday, July 11, 2002 5:06 PM
> To: Volpe, Christopher R (Research); 'David Gobbi'; Lisa Avila
> Cc: vtk-developers at public.kitware.com
> Subject: RE: [vtk-developers] Speeding up raycasting on x86
> 
> 
> 
> 
> 
> >2) It's not completely correct. Tests I ran not too long ago 
> show that the 
> >process causes the value
> >to be *rounded*, but this is not readily apparent because 
> the rounding is, 
> >in this case, not to the
> >nearest int but to the nearest fraction of 1/2**16. So, for 
> example, a 
> >value greater than (3.0 -
> >1/2**16), but less than 3.0,  will be rounded up to 3. This problem 
> >becomes very readily apparent if
> >you tweak the values so that you use the full 32 bits for 
> the integer 
> >portion and don't reserve any
> >bits for fixed point fractional values, thus causing rounding to the 
> >nearest integer.
> 
> Being "not completely correct" may cause big problems in the 
> ray caster.

Yes, butit's easily fixable. My version, for example, doesn't have the problem.

-Chris