Le 05/07/2010 15:24, bruno71 nous fit lire :
> Hello,

> #declare p1 = plane {<0 0 1>, 10}
> #declare p2 = plane {<0 -0.0141 0.9999>, -10}

> it should be a sphere cut by two almost parallel (xy) planes, however the second
> plane (p2) is visualized as a perpendicular (xz) plane.
> With:
> #declare p2 = plane {<0 0 1>, -10}
> everything is fine. It seems that the problem occurs when the y component of the
> normal vector has negative sign. Is this a bug or there is something wrong in
> this simple input file? Thanks,
>   Bruno

The comma are optional, but 0 -0.0141 is a valid expression for a single 
number... so everything is fine, you provide only 2 components for 3D 
vector, so it get extended with 0 on z (and the x part is small enough, 
so the plane is oriented like +y.

Use comma in vectors.

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