# Back-face culling in Calavier / Cabinet view projections - solved

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Hi, I have problem, that I don't know how to test weather the normal of face points to projection plane or not(can I see it or not). In case of perspective or orthographic projections it is easy to determine this, but using Calavier or Cabinet projections I should deal with angle... Cavalier x' = x + cos(a) * z; y' = y + sin(a) * z; Cabinet x' = x + cos(a) * z * 0.5; y' = y + sin(a) * z * 0.5; Maybe someone has an idea? Or at least knows where could I find the solution? Mindaugas [Edited by - VersusOm on June 24, 2007 1:36:18 AM]

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Solved! :)

As we know Cavalier projection has an angle, that is between the projection plane and direction of the projection. To determine the visible faces all we need is to check angle between its normal and direction of projection.

Calavier: dop = (cos(a), sin(a), -1)
Cabinet: dop = (cos(a)*0.5, sin(a)*0.5, -1)

dop - direction of projection
n - normal (transformed to camera space)

now to determine weather face is visible or not we do:

visible = dop*n < 0;

Mindaugas

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