[Fluxus] lighting the inside of a sphere

[gabor papp]

i'm trying to light the inside of a sphere, but can't figure out how to
disable the default light. is this possible? with the default light on i
get a big white circle in the centre that i would like to avoid.

i also had to invert the normals of the sphere to see the inside. is it
possible to make the polygons double sided somehow?

any help would be appreciated.

gabor


(clear)
(backfacecull 0)

(define l
    (make-light 'spot 'free))

(light-diffuse l (vector .2 0 0))
(light-position l (vector 5 5 10))

(define s (build-sphere 30 30))
(with-primitive s
    (scale (vector 10 10 10)))

(with-primitive s
    (pdata-map!
        (lambda (normal)
            (vmul normal -1))
        "n"))