[info-performer] removing roll from camera without resorting to the use of euler angles

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From: Bram Stolk (bram++at++sara.nl)
Date: 09/24/2002 02:03:32

Hello,

I have a 3d math question:

I am trying to remove roll from an arbitrary camera transformation.
My camera points to +y, so basically I need to remove the z-component in
the x-axis, and reconstruct a new x and z axis perpendicular to my
y-axis.

How can I force the x-axis of my cam trf to lie in the xy-plane
without disturbing my original y-axis?

My original approach of projecting x onto xy, and then
z = cross(x,y) is not enough, as x and y no longer form a 90
degree angle after projection. Adding an additional x=cross(y,z)
re-introduces the z component in the x-axis that I was trying to
remove.

Note: I try to avoid the obvious approach of using Euler angles,
as Euler angles are evil, as pointed out by Steven Baker (and quite
rightly so):
http://www.sjbaker.org/steve/omniv/eulers_are_evil.html

Thanks,

  Bram Stolk 

-- 
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 Bram Stolk, VR Specialist.
 SARA Academic Computing Services Amsterdam, PO Box 94613, 1090 GP  AMSTERDAM
 email: bram++at++sara.nl   Phone +31-20-5923059  Fax +31-20-6683167

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