raycast to exclude object to be illuminated from selected lights

hi there

Blender Internal has a layer link tool for lights. In Cycles you can use render passes and exclude function to do the same. But that doubles or more the render time. Not a very economical approach when you only want to fully exclude a ground plane from extra mesh lights.

Is there a way to use the ray cast tools to simulate the light exclusion? Does anybody have any idea if this is possible or are we stuck with render layers in Cycles?

No one has an idea?

did you check the object panel or may be light panel

there are some light rays you can control


Hi Rick

yes those options are only affecting the selected mesh itself but do not allow you to design relationships to other meshes. As it looks Jonathan from CGCookie mentioned that he also does not know about any other way to do this besides using render layers. The new exclude option is a nice addition but still increasing render time because for each light I would like to modify and prevent hitting the ground plane I would need a new rendering image/pass - sadly.

in cycles there are also the lightpath node
that can select some rays

don’t know if that help!

this node set up is for cycles ?


yah I tried understanding the light pass but I am failing at it :slight_smile:

I was watching few tutorials and as it looks the lightpath node helps when you want to make an object interact with a shadow diffuse or something ray for the camera.

The lightnode would need the ability to also use a material index or diffuse index to prevent the ground plane being light by selected meshlights, I think if I am correct.

did you check this one for object

see bottom panel for cycle
control diffuse glossy trans

is that what you want ?


that is the global function you can exclude it form every other objects.
the old blender internal allows you to limit light to objects at a layer and thus you can establish local or individual light links.

Ray visibility would be awesome in case you could also make it per object or objects.

so it is confirmed

light links to objects are not possible with Cycles right now. the only way are time consuming render passes with the exclude function.

did you try on IRC
might get a better answer there !

now should light on different layers illuminate ob on these layers only like in BI?
did a test and seems not
unless you do it with composite and make render pass per layer!

there is Light Falloff node

which determines distance at which a lamp affect things
could be usefull for some objects if far enough from lamps and other objects!

in object panel there is an index pass number which might be used for layer and object info node


Well I would like to prevent using render passes when not needed.
Currently there is simply no light object relationship tool.
Only through separating objects into layers can you get the desired effect.
But that way while great for compositing control just increases render time significantly.

However I am sure that at one point they will build this into Cycles as well.

not certain where may be on IRC
you colud ask tog et a new feature like this !

it would be interesting!

happy blendering

I could but actually I am very sure that they think about this already on their own.
Blenders Internal was very basic a layer based light link option.

Maya has a more complex per object light link function that works better but layers will do it.

How that can be coded into Cycles I don’t know. I could send Ton or Brecht an email.

any new news on this? (this layer only) or groups functionality to lamps would lessen work time considerably.