View Full Version : Scaling point lights

08 August 2004, 11:38 PM

can't find the thread anymore, the technique was described at cgarchitects. It wasn't possible to do it in LW, only in Cinema and Max, what I mean is to scale the point light to fit the room and to fit the light attenuation accordingly and to uncheck specular. Unlike LW I'm able to scale the point light, but it has no effect on the room, even turned into an area sperical light nothing changes like it should.

Not possible in XSI??

08 August 2004, 11:45 PM
Don't think so... Scaling only makes the indicator larger.

08 August 2004, 09:15 AM
You can't scale lights in XSI.


08 August 2004, 01:36 PM
Oh that's a pitty, it would make lightning rooms much easier. I already hoped I had the 'eierlegende Wolmilchsau'. :sad:

08 August 2004, 01:46 PM
you can turn your point light in an arealight (without shadows) and set the geometry to sphere and then use the xyz scaling to get what you describe it... I'm doing a fast pre.viz for a studio right now.. it's the way I choose to illuminate a big space where the ceiling is 'casting' uniform 'diffuse' light.. take only care that the intensity of the light.. will vary greatly when you scale your arealight.. do not be worried about the use of arealight.. coz without shadows is really fast.. and it gives anyway a good shading on your objs... you can then get the shadows from an 'ordinary' point light.. in my case I just use an ambient occlusion for also the 'direct' shadows.. coz the visual goal is to simulate radiosity rendering... but in this way I'm under 30mins for shot.


08 August 2004, 01:51 PM
changing the falloff is what you are after by the way.
XSI has no OGL display for point lights falloff (bit of a bugger but nothing major), but that's what other SWs do when you scale lights down.

if you really can't do without a visual feed back get 2 implicit spheres of radius one (they won't interfer with rendering) and setup 2 expressions in the light falloff that will pipe the scaling of those implicits to the falloff radius
pipe the falloff radius of the light into the implicits' radius so that when you change the light properties you get visual feedback.

08 August 2004, 02:15 PM
Thanks francesca, I tried this yesterday with little success, repeated it again (with more sleep) and it worked good enough. What I am after is here

I think I can cope with area lights.

It's all about playing with falloff to get it right.

ThE_JacO, it's a little bug but I incidentally found an easy workaround, just turn your pointlight into a spotlight, press b and tab until you get the falloff handles, now turn the spotlight back into a poinlight and the handles stay visible, BUT don't change the viewport or you'll have to do it again.

08 August 2004, 02:22 PM
what exactly is the bug in all that?

08 August 2004, 02:29 PM
Sorry again francesca, the scaling only works uniformerly, I need the y scaling down, but it has no effects, neither has the z axis , changing the x has great impact. I'm not able to light the top and the bottom as the sides, could you please give me some more cues or a little scene I could dessect :love:

ThE_JacO, the bug is that the handles are normally not there for pointlights as they should, only through this workaround. I would call this a bug, not a big one, but a bug nevertheless. Not every bug has to kill your scene or crash you pc you know ;)

08 August 2004, 03:27 PM
it's just an OGLgizmo to Parameters connection persisting longer then you'd expect.

a bug is a different thing :)

I still fail to see how it's useful since it only controls the angle, it doesn't allow to manipulate the falloff.

also if you create the light as point and convert it to spot it won't show the manipulator here, it needs to be created as a spot with the angles properties here for that exploit to work.

I'm surely failing to understand something here.

08 August 2004, 04:00 PM
I'm surely failing to understand something here. it's more probably me :) but I'll give it another chance.

If you have the properties window of the light open and you drag the OGL handles you'll see how the start and end falloff will change in the prop window, I didn't know there was a way to change the angle of the falloff, isn't this related to the type of light? A spotlight will have an angle a pointlight doesn't. The OGL falloff handles for pointlights look like those from the spotlights but stil behave like like it should for pointlights.

Do you want me to post a few screenshots??

08 August 2004, 04:34 PM
no time right now to look at your problems.. I have already mine.. :)

anyway a screenshot for the light setup I'm working on.. really the first implementation.. hope it helps.


08 August 2004, 06:55 PM
awesome fransesca! No need for more explanations, you screenshot explains everything, you use several lights as opposite to one like the tut at cgarchitects, mostly cylindrical area lights for the ceiling, that's why your scaling parameters work on all axes.

Thank you very much for your time :thumbsup:

08 August 2004, 06:08 PM
Not exactlly related to falloff but talking about size of lights, In SI 3d If you had a very VERY large object and your light icons lloked really REALLY small then speculars were very small and sharp ( not the same effect as setting the specular sharp and tiny in the material, more a light object size relation) I discovered that by accident once I had a very big scenario with lots of objects inside. After that I used that trick very often when I had metals, specially golds to get losts of shiny points of specular reflection moving around. But I have noticed that if I try the same thing in xsi the size of my objects don't do any change nor the size of lights of course. Did anyone else use this trick and is it possible to do in xsi? without affecting the material of course, because it was not only a matter of specular size but more of the way those speculars behaved and moved more lifelike because in real life it is very common that lights not to far from the subject (let's say a ceilling to floor distance) are reflected like tiny points and not as big as in 3d apps where by default lights tend to look as if they were very big illumination sources ( IMHO )

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