Using independently two values of two object that share the same material

Question

I have two different objects that share exactly the same material, so same nodes. I have let's say one emission node, is it possible to get different values for both objects while still keeping the same material ?

Answer 1

You can store a per-object variable as a Pass Index, which is accessible by your material, via an Object Info Node:

Or, one way or another, you could store the variable on the object's geometry, in which case you have the option of varying the material across the object's surface, possibly in a different way, per-object:

That would be read via an Attribute node in the material. (,here, The attribute's name is for convenience only, you can call it whatever you like.)

You can assign more geometry-attributes if you need them, and combine and/or map them to influence any material settings you like.

.. so, for example, these two objects are in the same orientation, and share the same material:

Answer 2

Yes, of course this is possible. In the following image, both spheres have the exact same material called "red light". But the emission is driven by two Attribute nodes, one which the manipulates the Hue of the given color, and one which sets the Strength on the Emission node:

The crucial thing to achieve this is, the material needs an Attribute node (or several, depending on how many individual values you want to manipulate) set to Type: > Object (in this case Instancer works too, but not always) and the Name of the attribute must reference an attribute which is added as custom property in the Object Properties, so both objects need to have these Custom Properties. In this example, the left sphere has a "hue" value" of 0.5 (leaving the original color) and a "strength" value of 0.5, the right sphere has a "hue" value of 0.15 (changing the color) and a "strength" value of 20:

By default, when you click the New button under Custom Properties, a new property is created set to Float values and a Min and Max values of 0 and 1. But clicking on the cog icon to the right lets you edit these settings, the name, the data type, the min/max range.

I've used the hue change for changing the color, you can also make properties for saturation and brightness. You can also insstead of Float use the data type Float Array, which gives the property multiple float values (3 by default), so you could use this to enter RGB values directly. In this case you have to use the Color or Vector output of the Attribute node.

The good thing with this method is, you can even use drivers to change the properties on the objects individually. If you would use drivers directly in the material, it would be one driver changing the material on all objects together, not separately.