Lighting Types

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Old 12 December 2003   #1
Lighting Types

Knowing full well my lighting skills need honing, I started looking around for lighting tuts.
I found some good ones on CGArchitect but upon reading them, they are for Autodesk VIS.

My question, they have a light setting 'ambient-only' which is spearate fron diffuse and specular. How can that be? Surely an ambient light *must* affect diffuse? After all, how can you have a light which casts shadows and lights a scene but does not react to the diffuse setting of an object?

Their falloff has a near & far attenuation as well. Strangely the -ve density on shadows makes it darker rather than lighter.

If anyone has experience of Autodesk Vis and can shed some light on this i'd be grateful, (pardon the pun).
Can the light type be cross-referenced to LW? or is it that Vis is more suited to lighting, (call me biased but I'd think not ).
 
Old 12 December 2003   #2
Not really understanding what you're after, here's what comes to my mind.
In Layout, you do have an ambient default light, for which you can set color & intensity.
If you're talking about radiosity, there is a "Background Radiosity" mode, that use a background image to enlight the scene. This won't use the model colors to bounce, but only the background image. It's kind of ambient radiosity, though it does cast shadows.
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Old 12 December 2003   #3
Here`s a link to a great video tut, it`s just the basics thou but i found it very educational

lighting tutorial

on the bottom of the page, hope it helps
 
Old 12 December 2003   #4
It's more about how I can transfer what the tuts are saying into "LW terms".
As I say, they use 'ambient only' lights - so are they in effect radiosity?

Just trying to get a handle on the explanation of the lighting used.
They were the tutorials on cgarchitect.com for lighting.
 
Old 12 December 2003   #5
The ambient only is like the ambient setting in lw but restricted to a single light vs. to the whole scene. You could use diffuse only light for this in lw.

Florian
 
Old 12 December 2003   #6
So am I right in assuming that Vis has no 'global' ambient setting?

It just struck me as if th tutorial was setting up multiple 'ambient only' lights, suggesting their size/location/rotation had an impact on how 'ambient' was handled.

Or are they really the old trick of a non-shadow casting, non-specular light for 'fill' as is done in LW for 'faking' radiosity ?

On another light type, is the near/far falloff a band, i.e. the light can become a 'ring' by controlling these settings, or is it just where falloff starts and 'far' is the point at which it is totally black?
 
Old 12 December 2003   #7
Quote: Originally posted by colkai So am I right in assuming that Vis has no 'global' ambient setting?

No, VIz does have this setting in the rendering - evironment settings.

Quote: It just struck me as if th tutorial was setting up multiple 'ambient only' lights, suggesting their size/location/rotation had an impact on how 'ambient' was handled.

Or are they really the old trick of a non-shadow casting, non-specular light for 'fill' as is done in LW for 'faking' radiosity ?


Thats what they are supposed to do. I dont really know if there is a big difference between and ambient and a diffuse light. The only thing is, that an ambient light cant cast shadows.

Florian
 
Old 12 December 2003   #8
Quote: Originally posted by Limbus
Thats what they are supposed to do. I dont really know if there is a big difference between and ambient and a diffuse light. The only thing is, that an ambient light cant cast shadows.

Florian


Ahh,
gotcha! makes more sense now, thanks.
 
Old 01 January 2006   #9
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