Hi,
>1. In argInit(...), does anyone know why the the
>second row of the 3x4 projection matrix is subtracted
>from a multiple("image height-1") of the third row?
>This is equivalent to turning the image coordinate
>system upside down, I think.
Yes.
>2. In argConvGLcpara2(...), after the QR
>decomposition, when the projection matrix is converted
>for OpenGL: Can anyone point me to a reference that
>explains this operation, or tell me what and why it is
>being done? It seems to be a basic operation, I don't
>know.
In the ARToolKit, screen coordinates are represented in
PIXEL unit. For example, a image with 640x480 size has
[0-639] range of value in X axis and [0-479] range of value
in Y axis.
In order to use such camera parameters for openGL,
it should be convert for openGL representation.
Basically openGL uses [-1,1] range of value for normalized
clipping volume representation in X,Y,Z axis.
So [0-649] range and [0-479] range should be convert to [-1,1] range.
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Hirokazu Kato
Faculty of Information Sciences
Hiroshima City University Phone: 082-830-1705
Email: kato@s ........................ Fax: 082-830-1435
URL: http://www.sys.im.hiroshima-cu.ac.jp/people/kato/
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