In Blender 3.0, how can we control instance properties (scale, etc.) by proximity?

Question

I've been looking at tutorials and various node tree screenshots, but since the 3.0 release many aspects of Geometry Nodes have changed, making those sources largely irrelevant.

In 3.0, how can we use an Empty to scale / rotate / etc. a bunch of instances?

^{Above: Icospheres generated at each mesh point, and an Empty I want to influence them with.}

My node tree so far:

I have been trying lots of different things to scale these (100% effect where the Empty is, and tapering off to 0% effect beyond a certain radius, such as the radius of the Empty object).

Also, it would be nice to be able to adjust the falloff curve.

Answer 1

You don't need geometry proximity to scale by prox to an empty. You just need to check the distance to the empty:

Here it is with a falloff curve (using RGB curves node, but a float is a float.) I'm clamping it to the 0,1 range (and inverting it) before the RGB curve for convenience-- anything more than 1 unit away will get the minimum scale I have in my curve.

Edit: Here's a pic from the file Mentalist offered in comments:

Gordon Brinkman also offered that we can just use distance instead of subtract+length.

Answer 2

You can use a Geometry Proximity node if you want, and your setup was close. Here's a version of your node group that works:

In this example, notice that I use an Object Info node, rather than an input to the Geometry node group. That gives me the geometry location of the empty. The only other change from your setup was to plug the distance output of the Geometry Proximity group into the Scale input of the Instance on Points node. This uses the relative position of the empty to control the scale of the icospheres:

EDIT: There seems to be a lot of confusion in the comments about the difference between this approach from the accepted answer and the approach I've described above. Here's a version of the other approach, simplified to highlight the major difference:

The geometry proximity node has been replaced by a proximity calculation using vector math. Both approaches work with an empty, because both approaches calculate the distance from the target object to a point. In both cases the point is the location of the empty. In both cases, the empty can be replaced by other objects, so long as their location is used.

The difference as Nathan has pointed out by example in the accepted answer is that my approach gives a single value for distance — the distance between the location of the empty and the nearest face (in the example) of the target object. (It could be the nearest vertex or edge, depending on settings in the Geometry Proximity node.) The other approach gives the distance between the location of the empty and every point on the target object.

Use my approach if you want a single value, ie for uniform scaling of instanced objects. Use the accepted approach if you want a field of values, ie for scaling that depends on the distance to each instance.