Lew Hitchner (hitchner++at++netcom.com)
Sat, 20 Nov 1993 09:10:41 -0800
8) Our virtual reality systems operate in a different
coordinate frame from Performer, it is not possible to modify
our existing system as it encompasses a lot of
hardware/software (tracking, sound, collison detection, etc)
some from external suppliers. This gives me a number of
headaches and makes it very difficult to use some Performer
functions including pfESky and pfBillboards which use the eye
heading, roll, and pitch to operate. Is there any way to get
performer to change its coord frame? Simply
rotating/translating the channel viewpoint does not appear to
work - the sky flies all over the place when you change
orientation.
If one doesn't exist how about a user settable flag to indicate
what coord system your using. After all, Performer doesn't
agree with GL, and SGI worked for 10 years to get GL accepted
as a standard. Theres a lot of code out there aimed at the GL
coord system, and it can be a pain to convert.
I second David's suggestion/request. Our Performer application we
built at NASA Ames evolved from an existing application that used GL
coord. axis orientation. Although it was fairly trivial to just
compose a matrix transformation with the view matrix prior to each
pfFrame (I should say, "trivial" once I figured out how Performer's
view matrix transformation is composed since that's not clearly
described in the documentation), it still left a lot of design
headaches due to having to think about two different coord. systems
simultaneously.
Lew (the documentation gadfly) Hitchner
Xtensory Inc.
Scotts Valley, CA
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