## [visionegg] map singratings on cylinder

*From*: Kaspar Müller <kaspar.mueller@xxxxxxxxxxx>
*To*: visionegg@xxxxxxxxxxxxx
*Date*: Thu, 20 Dec 2007 11:52:43 +0100

Hi!

`I would like to project singratings on a round screen, therefore I
``need to correct the distortion in such a way that the grating-bars
``have the same width everywhere.
``I tried to map singratings on a cylinder, but somehow the projections
``don't work. singrating3d doesn't work at all (is this class not
``supported anymore? I didn't find it in the visionegg library
``reference), and for singrating2d I didn't find out how to do it. I
``tried to change vertex coordinates in the gratings class, and I also
``tried to work with projections, but neither worked.
`

`Unfortunately, I can't use the spheregrating class, since (1) I need
``colors, and (2) I need the projection the other way round (at the
``sides of the screen, the grating has to be narrower than in the center).
``The mapping function for the horizontal coordinates should be
``x'=R*tan(x/R), where R is the radius of the screen, x is the position
``where the ray would hit a flat screen and x' is the horizontal
``coordinate on the screen.
`
Any idea how I could manage this?
Thanks, Kaspar
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