Subject: clarification on hits function

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A student asks (more or less)

"The notes use V as the viewpoint,  but how do I access the
view point in my "hits" functions.

Dr. Westall responds:

I should have been more clear on that today.   Initially, "the viewpoint" will
be the base (or origin) of the ray.  Later on ray's will bounce around and
so it will NOT be possible to assume the viewpoint is the base of the ray.

double sphere_hits(
object_t *obj,
vec_t base,       /* ray base */
vec_t dir)        /* unit direction vector */

Hence you should use the parameter variable "base" that is passed to your
hits function wherever "V" or viewpoint appears in the notes.