Why does my light shine through walls?

[edlundart]

Hello fellow animators,

For my short film, I'm trying to create a certain lighting effect using a directional light. I'm working with Ambient Occlusion. I tried adding a light, but it always appears as a spherical light source casting light in all directions. Instead I added the rim light that is default in any chor's PWS to my choreography, and that light is indeed directional. So cool, I thought I had it all figured out. The thing I don't understand is, the light is shining through walls. I'm trying to have the light partly obscured by a wall, but even if I aim it in the center of a wall, the light is just as strong on the other side of the wall!

 

Is there some setting somewhere that will make my walls stop the light from going through them? Or am I missing some setting for the light itself? Maybe I'm using the wrong kind of light, but then how can I make a new directional light?

 

Any help would be greatly appreciated.

[Rodney]

The short answer (I think) is to add a second layer to the wall.

The light will pass through the first and be stopped by the second.

 

I use to have a pretty decent description of why this happens laying around here somewhere.

Its a necessary thing though to have the light penetrate the first level of geometry or else most models would hardly be lit at all.

Creating objects with actual thickness is generally the answer to the problem.

 

Again... I think this will be true in your case.

Apologies if it is not.

[edlundart]

Thanks Rodney. I tried to put six walls between the light and the room, but the light shines through them all. Does that satisfy the need for a second layer of geometry? Or do I have to model the walls differently somehow? Maybe the problem is something else.

[Fuchur]

Thanks Rodney. I tried to put six walls between the light and the room, but the light shines through them all. Does that satisfy the need for a second layer of geometry? Or do I have to model the walls differently somehow? Maybe the problem is something else.

 

I dont know exactly, but just to be sure:

Does the light have Shadows activated? If not, try it out. (You can set that in the properties of the light.

You can even give the shadow-darkness a very low value (for example 0% oder 10% if you dont need the shadow, but it could help you with your problem here.

 

The other thing: Every light has got a property where you can set the light-type...

Every light is created with the default-value "point" but you can change it at any time.

You can set each light to point, sun or spot and it will behave like you expect it.

 

*Fuchur*

[Fishman]

I vaguely remember this is a problem with z-buffered shadows. You may want to try ray traced shadows to see if that solves the problem.

 

Scott

[Animus]

If a light doesn't cast shadows, it will go through all geometry. In the default chor, the directional lights have shadows off. Otherwise, I don't know.

 

Michel

[Kelley]

I think what Rodney was getting at is: If you have [let's say] a single four-point patch as a wall [we'll assume it's a large one] the light will pass through. But if you have a cube, the light won't. If you just put another four-point patch in front of the first, both will pass the light.

 

I've noticed when texturing, some times I can go to the top view and select only the right-hand side of several objects. When I go to the Front View, they frequently overlap each other. However; I can apply a decal to the group all at once, and the front patchs don't mask the ones behind. So the question is: are you walls only single patch thickness?

[edlundart]

I seem to have fixed the problem, but I'm not sure which one(s) of your tips did it! Thanks to all, at any rate. I think part of the answer is to have denser geometry.

[Kelley]

I think part of the answer is to have denser geometry.

 

I suspect you're right. Here's a demo I cobbled together: a cylinder with a hole, and four 4-point patches stacked inside. A spotlight directly above shines all the way through, while a spotlight behind the cylinder is blocked. [tho' it can blow around around the edges.]