Why can't this simple object be fed with a float value?

Question

I want to get the length of the Y axis when a circle rotates dynamically changing the length of a cylinder, but the connection of the geometry node doesn't seem to work, I see both the output and input are float Type, am I missing any details?

Answer 1

As already correctly noted by Chris: You are confusing a field with a single value here.

A cylinder requires a single float value for the Depth when it is created. This is symbolized with a small circle.

An input or output marked with a diamond requires a field.

A diamond with a point in the middle can handle both (and switches automatically depending on what type the input is).

What is the difference?

You can think of a field as a list of values. The length of the list corresponds to the number of elements in a specific domain. For example, if you have a cube, the list of elements in the point domain contains exactly eight entries. If you query the position, you have eight vector entries.

So the task here is to filter out of the many values of your circle a specific single value from a certain list.

The field (i.e. the list of data) in this case is the position of the individual points.

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But now back to the solution to your question:

I tried to illustrate this simply, and in this example I first make a circle rotate.

Then I use the node Position to get the positions of all points of the circle, and from this vector I separate the float value for the Y-axis.

But now I still have a field (a list of float values), which corresponds to the number of points of the circle.

In this case the node Attribute Statistics helps me, because it returns the maximum value of all available data from a list of data.

And now I got a single float value, which is now also understood by the cylinder.