#Lighting weirdness
3 messages in this thread
GreG-
I ran across a situation that I can't figure out. I was trying to model a
street light of sorts and this is how it went. I created the main lamp part
(metal or whatever) and then added a sphere for the globe containing the bulb.
I made the sphere bright and added an axis inside the sphere and made it a
light source (point light, casting shadows, controlled falloff). When I
rendered it using SCANLINE everything was fine, it gave off a nice soft glow
under the lamp, but in TRACE mode I guess the sphere caused the light source to
not be seen due to the shadowcasting. I then deleted the axis light source and
made the sphere (globe) itself the lightsource. It still did not cast light in
TRACE mode. And in SCANLINE mode it casts some strange looking pattern on the
ground. Is there a way to put a lightsource inside a globe-like thing and
still have shadows casting from that light? I tried moving the light source
outside the globe but the shadows are strange and unnatural looking. I ended
up rebuilding the lamp without a globe at all and it does fine now, but I still
would like to know if "realistic" lights can be built like I described above.
I hope this made sense.
Thanks
Darin
Darin,
Ok, I knew where you were going once I read you modelled a light. <g>
A light source is defined by the axis of an object itself. In the case of a
sphere with the axis at the center, the light is emitted by the axis. Knowing
this, lets take both Scanline & Trace and see what's happening.
In Scanline mode, lightsources will not be obstructed…they will pass through
objects as if they are not even there. They also do not cast shadows. This is
why you see the scene lit, with no shadows.
In Trace mode, lightsources will work as they do in real life. The axis in
your sphere emits the light. The light rays start their trek towards the
opaque sphere. They are not able to pass through and shine on the scene. They
are for arguments sake, trapped. They are restricted to inside the sphere that
the are emitted from. Therefore, no light in the scene outside of the lamp.
To get the effect you want, you must make the sphere somewhat transparent to
allow the light rays to shine through. Another method, is to make the sphere a
FOG object with a FOG setting of ".01". This will allow light to pass through,
as well as make the object appear to be BRIGHT. Around this FOG object you may
also want to add another sphere made of glass. This would add to the realistic
look of it.
Hope this makes some sense.
-GreG
GreG-
Thanks for the info. I knew, more or less, why it wasn't working, I just
figured there was a way to make it work. You told me what I needed to know in
that regard. I actually thought of both transparancy and fog and even thought
I tried to add filter values to the sphere, but I did not take a lot of time
trying it and must have not quite got it set right. Thanks again.
Darin