I love the idea of procedural modelling, but I'm having difficulty getting some really basic stuff to work the way I want.

I'm trying to extrude a tube a number of times with a series of poly extrude nodes, and would like to be able to change the number of sides the tube has once I have created the chain of poly extrudes. Attached is a really basic start to that.

The problem is, since I am selecting the end face for the extrude, and the extrude is based on prim number, when I go back and change the number of columns on the tube, the extrude is no longer coming off the correct primitive.

How can I ensure that the extrude is always extending the end primitive?

you'll want to use groups
on the first polyextrude
down where it says Output and Geometry Groups
turn on Front Group
give it a unique name - the default is extrudeFront - I'd use extrudeFront`opdigits(“.”)` - this will use the number at the end of the polyextrude1 node's name - so the group will be named extrudeFront1 for polyextrude1, extrudeFront2 for polyextrude2 etc
then in the second polyextrude use that groups name in the Group field at the top of the parameters
see the attached file

This is great, thanks so much for your help!