Mike Metheny wrote:
> 
> Will someone please tell me why the following code renders as it does?
> (place a camera at <0,0,-12>)
> 
> sphere{<0,0,0>,5 pigment{rgbf<0,0,1,.5>}}
> sphere{<0,0,0>,2.5 translate -2.5*x pigment{rgbt<1,1,0,.5>}}
> sphere{<0,0,0>,2.5 translate 2.5*x pigment{rgbt<1,1,0,.5>}}
> 
> gives me the image attached.  now; is it me, or, shouldn't the edges of the
> small spheres meet perfectly with the edge of the big sphere?  I say this is
> a stupidity problem simply because, well, it's obviously something simple
> i'm not getting.
> 
> --
> 
> Mike Metheny

  You are correct in assuming the misconception on your part was the key
 player in this little drama. A sphere represented as:

 sphere { <0,0,0>, 1 = a sphere "2" units across !!!

    A sphere with a radius of 1 is 2 units across. The sphere object
 is defined by it's radius and not it's diameter. With this in mind
 you can see where your large sphere is 10 units wide ( 5*-x and 5*x)
 and each of the two 2.5 unit spheres are suffering the same fate.
 To have them kiss surfaces at the outside edge of the larger sphere
 your translate values should be 7.5 and not 2.5 as used above.
   Beware of the same trap with the box object. If you specify it
 as box { <-1,-1,-1>,<1,1,1> } you will have a box that is 2 units
 wide and not one unit like it might appear at a glance. Where the
 comma is between the two fields can be though of as your origin line.
 The illustrated example shows you are designating the objects walls
 at -1, +1 from that origin point. 1 + 1 = 3 : )


-- 
Ken Tyler

mailto://tylereng@pacbell.net

Post a reply to this message