On Friday 28 January 2005 02:18, Curtis L. Olson wrote:
> Tiago Gusmão wrote:
> > Altough the billboard itself always faces the POV, you can still set
> > the normal the way the real light would be pointing to, them set a
> > diffuse light on the POV and enable backface culling.
> > I suppose performance hit should be minimal for TnL hardware.
> The normal only affects lighting.  Backface culling is done based on the
> "winding" of the triangle.  You would still see the light from every
> direction.
> Regards,
> Curt.

What about setting only one point at the beginning of the runway
and then calculating an angel between it and the normal of the billboard.
When the angel is > 90° or > - 90° the billboard is turned off when it is < 
90° or < -90° then on.

Best Regards,
 Oliver C.

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