How to have the same material applied on multiple objects, but control the material parameters for each object individually?

Question

I am making a modular road system where I want to apply an asphalt material with white road markings on many different roads (objects).

Now I want to be able to apply the same asphalt material to all these objects and then control for each object separately: the location of certain individual white road markings/ if they are full or dashed/ visible or not/ etc.

This way I can make more complex configurations like crossroads etc.

One way to solve this would be to make a different material for each object and use NodeGroups to make it easier. The problem is that I need many different combinations and that it would result in too many different materials to manage in a practical way.

I think the solution would ideally be controllable from within geometry nodes.

I attached the Blender file:

Answer 1

You can use the Martynas' answer, but without custom properties, by switching the Attribute node to Geometry type, then reading a custom attribute just like the u, and v attributes. Then you can save them inside geometry nodes:

The data is duplicated for each vertex, so for many attributes and dense geometries it could add up to something worth optimizing, e.g. this way:

Answer 2

You can control what happens in a material with custom properties of an object:

This way different objects with different custom properties can look different with the same material.

You can use Python to quickly create custom properties:

import bpy

for o in bpy.context.selected_objects:
    o["SomeBoolProperty"] = True
    o["SomeIntProperty"] = 1
    o["SomeStringProp"] = "Something something"
    o["SomeColor"] = (1,0.2,0.5,1)
    o.id_properties_ui("SomeColor").update(subtype = 'COLOR') 

Setting properties of the custom properties is a bit tricky(at least for me personally). I cannot find documentation for it. Anyway, the properties of custom properties seem to be accessible with object.id_properties_ui() and you update them with update() that has following description :

Python Console also gives some helpful error messages:

So apparently subtype can be

'NONE', 'FILE_PATH', 'DIR_PATH', 'FILE_NAME', 'BYTE_STRING', 'PASSWORD', 'PIXEL', 'UNSIGNED', 'PERCENTAGE', 'FACTOR', 'ANGLE', 'TIME', 'TIME_ABSOLUTE', 'DISTANCE', 'DISTANCE_CAMERA', 'POWER', 'TEMPERATURE', 'COLOR', 'TRANSLATION', 'DIRECTION', 'VELOCITY', 'ACCELERATION', 'MATRIX', 'EULER', 'QUATERNION', 'AXISANGLE', 'XYZ', 'XYZ_LENGTH', 'COLOR_GAMMA', 'COORDINATES', 'LAYER', 'LAYER_MEMBER'

I think 'COLOR' is the most useful here.