How to create a lightsource that only lights a certain object (and doesnt cast shadows)

Im looking for a way to create a lightsource (lamp or emission)… that i can use purely to create reflections on an object (for packaging shots etc).

So basically a contralable light source that i can put around an object to create a nice highlight or reflection in my object. This is what I would like to have

  • a light that doesnt make my object cast a shadow
  • a light that can’t be seen on camera
  • a light that doesnt effect anything else with its emission (so no effect on the backdrop for example)

Is this possible? Im in Blender 2.8 Cycles

Yes, it is possible in Cycles! Wanna know how or have you figured it out already?

@gtomorrow No i havent…so id love to know!

It’s a question of setting up the layers, mask layers and compositing. You need to put your light source and your object on its own Collection (layer) and View Layer. Here’s a (really) quick and dirty example:

This is Collection #1. It contains your object and a light source (in this case a plane with an Emission shader)…

This is Collection #2. It contains the other objects and lighting in your scene. The cube on the right is in front of our center cube so you need to create a third Collection with the rightmost cube linked into it. Right-click Collection #2 in the Outliner and under View Layer click Set Holdout. This sets this layer as a mask layer like in previous Blender versions. You with me so far? :smiley:

Finally you need to set up your View Layers (Render Layers in Blender 2.79 and before). You need to create the following View Layers…

  • Solo cube: Collection 1 and 3 checkbox on (Included), Collection 2 off (Excluded)
  • Main: Collection 2 checkbox on, the others off.

Now switch to the Compositing Layout window, create two Render Layers nodes, the first with your scene, View Layer: solo cube; the second Render Layer node: main. Hook these up to a Alpha Over node, connect tha Alpha Over to your Composite node and render away! You’ll end up with this…

If you want a common lighting on the entire scene, just put your lights (except your object’s light source) in its own Collection and include it in the View Layers.

Hope this helps with what you are looking to do. Cheers!