Does anyone know how to exclude specific objects from a Houdini light source?

Help appreciated

you can use the light linker pane

https://www.sidefx.com/docs/houdini/ref/panes/linker [sidefx.com]

Hi,

Thanks for that. That seems to have answered my question. Although didn't solve my problem.

The problem I am having is that I have a scene with a spotlight and the VlitFog for volumetrics. I also have another back light in the scene. The problem is that the backlight creates effects I don't want and I need to figure out how to tell the backlight not to affect or exclude the volumetrics, the spotlight with the vlitfog attached.

The light linker seems to only list objects. If anyone knows of a solution for that, that would be helpful

A simple example file and an image with the “unwanted”
is maybe helpy.

Hello matthias_k,

There's another way I know of, and is mentioned in the docs' at the top of the page in the link arctor gave you.

It's the light bank.

In a data tab of a view window there is a drop down menu that has the ‘Light Bank’ choice.

Selecting that will list all your lights in the file.

The last column named ‘Link’ is where you select the objects that will only be lit by that light.

The only thing I don't like about the light bank is that if you say add a new object at the object level, somehow that object gets added to the choice of all the lights in the light bank automatically.

At some point I'm going to make a feature request that once you assign an object/s to a light that you can lock it down.

Otherwise, if you already have numerous lights assigned to various objects in the scene and make a change at the object level; You have to go through the whole list in the Light Bank to set it again. Definite annoyance in work flow.

But besides that it's an easy set up.

On every object, on the Render tab, there is a Shading Tab >
a parameter called Light Mask allows you to include or exclude light in your scene.

in the attached scene I have 3 objects and 2 lights
in the light mask parameter if I remove the “*” and render I get nothing - because there are no lights in the mask
if I use the default “*” - then all three objects will be lit by both lights

if, on the sphere, I use this: * ^spotlight2 - then I'm saying "this object will be lit by all lights (spotlight1 and spotlight2), but NOT spotlight2
the light linker will help you do this by just selecting your light and selecting the objects you want that light to effect (or select the object and then the lights)

hope this helps

Hi,

Sorry, I forgot all about this post. And came back and noticed their were some replies. I created a sample scene to explain the issue so you understand the issue with volumetrics

The problem is that the v_litfog affects all lights in the scene. But in this scene, I want the spotlight to have volumetrics, and the backlight to affect all geometry, but not the v_litfog shader so you don't have that weird circuler back glow which doesn't look right

Attached is a scene file and pic so you understand

Like Michael said, there is a Render tab on your atmosphere object with a Light Mask parameter. In your scene it is set to *, which means all lights. Press the button right next to the parameter to select the lights you want or use the light linker.

Oh, there it is. I was looking on the V-litfog in the shop network and couldn't find a render tab.

ok, that makes sense. Thank you everyone for the help!