root@kunivv1.sci.kun.nl (Privileged Account) (03/29/90)
After shouting out loud for several months 'Sculpt rules the waves',
'Forget about Turbo (harhar) Silver' and stuff like that, I almost died on the
spot yesterday. It started with a call of one of my friends who got a problem
with Sculpt. He said that you couldn't make a spotlight or something alike.
After having a good laugh, I told him to find out what it was. Ofcourse, this
couldn't be true!!!
Now what is exactly the problem? Well, picture this...
Make a face ( ;-) ) with Sculpt and place a lamp above it.
What do you see (when you render it and look in the good direction)??
Exactly: what you're supposed to see... a lighted face.
Now add a cylinder to this scene. Open it's bottom by removing the middle
point at one end. Turn the cylinder until it faces the face with the open end
and move until the lamp is on the inside.
Now, you have a kind of spotlight, directed to the face.
In fact, it should shed light on the face.
Render the scene. What do you see?
Nothing. No light whatsoever on the face. Okay, the cylinder may be lighted
from the inside, but the face is totally dark.
The only thing that helps here is to move the cylinder further away from the
lamp. But that wasn't the idea!! I wanted light from within an object (which
seems very normal to me (lamps, candles etc.)).
I don't know what to think of this. At one hand, Sculpt handles VERY easy
and is reasonably quick. But on the other hand is a lamp within or close to
an object a very normal thing to encounter. Anyway, I don't like the idea of
light-sucking objects, since it leaves you with only one alternative: putting
lamps far away from objects.
Does anyone know how to overcome this problem?
If not, thanks anyway.
Patrick Atoon, University of Nijmegen
Email: a4B6@erato.cs.kun.nl
//
// P.S.: It's never too late to start your own crackpot religion!
\X/ Guru
----cs121jj@ux1.cso.uiuc.edu (03/30/90)
Try making the inside of the cylinder a mirror, to reflect all light inside the
cylinder outside into the rest of the world. I don't think this should be too
hard, as if you didn't care about the cylinder (what it looked like and if it
was astheticly pleasing and so forth), you could just make the whole cylinder
a mirrored object and do the same object placement.
Also, have you tried a cone so that the narrow (open) end was facing the face
and the wide (closed) end was parallel to the point light source? [I would
tend to think that this way, only light rays that are parallel to the opening
would escape.]
You could even combine the two ideas above and see what happens. Also, try
(for an approach that is object-resulted) making a disc that is luminous and
placing it where the spotlight would end up being shown. If it is on the floor
of a stage where the curtains are drawn (for instance), then you could put half
of the disc on the plane of the stage & perpendicular to the curtain & half
of the disc is not visible, so there would only be a semi-circle visible from
the front of the stage {all 3 requirements must be met there}.
Just tossing some ideas at you...I can't guarantee any of them because I don't
have SA4D installed on my machine (yet)...
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Jeff Nicholson jeffo@mrcnext.cso.uiuc.edu Amiga is #1!!!!
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