On Fri, 29 Mar 2002 17:47:32 -0500, "Timothy R. Cook"
<tim### [at] scifi-fantasycom> wrote:

>Er, if you can test if a point is inside or outside the object, you
>can test if it's exactly on the surface (i.e. point is neither
>inside nor outside the object, or both, it must be coinciding)

No you can not. There's such a thing as limited floating point
precision. You may *assume* a point is on a surface but there is no
guarantee. For you, acos(sqrt(2)/2) may be equal to pi/4, but for a
computer it is not. Computers just can't deal with infinitely long
numbers.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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