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View Full Version : Near/far Attenuation of lights?



cresshead
12-07-2003, 07:19 PM
hi

i'm trying to see if lightwave can do a similar thing to what lights in 3dsmax can do in that you can define where a lights starts and ends in max...as well as have a decay setting...

can you do this type of thing in lightwave or if not how wold you work around it?

http://www.lightrays.de/html/tutorials/scheinwerfer/tut_spotlight_eng.htm

colkai
12-08-2003, 04:00 AM
Damn,
I've just been asking about this on CGTalk - there are a couple of lighting tuts but they use this and also the 'ambient only' light setting - which seems, implausibly, to be distinct from both the diffuse and specular channels.

How can one have a light source that doesn't affect the diffuse, but affects the scene light?

Craiglet
12-08-2003, 07:17 AM
I've not used 3DMax but Lightwave lights do offer falloff settings, with various types of falloff which produce the effect you seem to be asking about.

You also have the ability to set any light to affect or not affect diffuse and / or specular, using the checkboxes on the light properties pane, as well as exclude any object or objects from any light...

As far as ambient light, one of the first things I do is turn it down below 5% or off altogether... It just doesn't look realistic. I often use a pale orange Spotlight with a shadow map (turn up the fuzziness) as a key light, a soft pale blue distant light for fill (point it the opposite way of the key), and another spot around back pointing into the camera for a rimlight or kicker -- as a good basic setup. Don't be afraid to turn lights above 100% as you tweak to get the look you're after.

colkai
12-08-2003, 07:20 AM
That's what is curious about the 'ambient only' setting in the Viz lights, it suggests a directional ambient that *doesn't* affect diffuse if the diffuse box is not checked.
Which to my mind seems, well, just plain impossible - how can one *not* affect the diffuse?

cresshead
12-08-2003, 08:14 AM
maybe this make more sense...

i want the light not to work for the near part of it's beam then switch on for the lamp area...

simple in max but not so sure for lightwave...

Craiglet
12-08-2003, 08:41 AM
Yeah... okay. There is no way to do that in LW that I know of... However, the exact rig you show should look just fine unless you are using volumetric lights... normal lights don't show in mid air until they hit something.

Otherwise just move the light down inside the lampshade and cheat the cone angle out a bit wider. Remember, the physics behind it don't have to be real, it just has to look "right"... It's all about the final render.

trick
12-08-2003, 08:51 AM
You can cheat a little by making a copy of the same light, reverse polarity (example: one light +80%, other light -80%, or more...)and reduce the falloff of this negative light.

If it is only for the volumetric effect: look at the parameters because a near range can be defined !!!

colkai
12-08-2003, 11:32 AM
In that particular instance, unless the volumetric effect of the light is needed, then I wouldn't use a cone, but a point light, as a bulb is. If i wanted cone light, say for shadowmaps, i'd put two back to back with a wider angle.

Having said this, I know what Cresshead means, it would open up a whoel new range of lighting if the 'near attenuation' was available.

cresshead
12-08-2003, 04:08 PM
got it working..sort of!