Emanuel Brzostowski wrote:
Hi Artur
Ok, just found a statement in this group (forgot where), telling me, J3D is
using floats internally. So the question arises, why i can use doubles nearly
everywhere (except for the reason of decreasing performance)?
Wouldn't it make sense, to let J3D use doubles internally (everywhere), and
converting them to floats only when nessecary (i.e. when passing the data to
DirectX or OpenGL)?Imho this would drastically increase the accuracy of
transformations (and maybe, as well decreasing performance :( ).
I admit that i don't know the internals of J3D as good as many other people
in this list, but i would like to know, the hows and whys (concerning the
float vs. double problem), or at least a pointer to some information about this
topic.
-emanuel
Under Solaris (and Sun's brand of graphics card) both the test
program from you and in bug report 476087 works fine for big float.
Note that the precision pass down to the Opengl call
is the same (JDK use same precision under windows and solaris).
This is driver/card floating point precision problem
which is not pixel exact when vertices of big float
pass down. Probably it is loss in the T&L engine of the
pipeline.
That's why game card is not good for 3D CAD design in workstation.
Check out,
http://www.3dlabs.com/product/technology/wildcat_quality.htm#sub-pixel
- Kelvin
-------------
Java 3D Team
Sun Microsystems Inc.
Emanuel Brzostowski wrote:
I just can't believe, precision of double is'nt sufficient for the
given
testcase (but obviously i'm wrong).
Float, not double. There are many places internally where java3d uses
floats, converting from doubles if needed. And precision of float is not
sufficient for your testcase.
Artur
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