How to create a geometry-node-based generator for columns with a custom side profile and custom amount of sides)

Question

I'm trying to create a geometry node based generator that gives me control over the side profile of a column-like object. I tried to do this with a custom curve window (which can also be accessed by beveling an edge with a custom profile), but I don't know how to adjust the general shape (for example, if I want a square column with 4 vertices, 12 for a circular one). Also, I wanted to control the vertical number of edges so that I can easily create multiple resolutions of this column (so, for example, 20 edges create a smoother side profile than, say, 10 edges)

I have attached an image showing an example of a desired result. Blue shows the side profile. In this example, my general shape is 4 because it is square and the vertical edges are 111.

If my wishes are possible, could someone explain to me how to achieve the desired geometry node setting?

Answer 1

Here is a solution. Limitations: only the y-displacement of the curve is evaluated. Height of column has to be aligned to z-axis.

The basic idea is, to create a cylinder and move the vertices of its vertical edges along the normals of these edges. This shall be based on the displacements of the vertices of a resampled curve. The original curve will be provided as an input parameter.

Details are explained below.

How does it work

The following nodes generate the cylinder. Most of its input parameters are published to the Group Input. This makes it easy, to configure the column, that we aim for.

The following nodes execute the displacement of the vertices:

The direction is determined ty the normal of each vertex. We project this onto the XY-plane, because the normal of the topmost and lowest vertex is not orthogonal to the z-axis. We normalize this, so that we can define the length by a calculated value, that I called Y-Displacement.

The following nodes calculate this value:

In the lower frame, we resample the profile curve, so that its number of vertices corresponds to the number of side segments of the cylinder. We do this, because, we want to take the first vertex of the curve, to modify the indices of the topmost segment and so on.

We calculate a z-index, to map the segments to the indices. The vertices of a cylinder are organized counterclockwise for each side segment from top to bottom.

Next we use the calculated z-index to access the position of the corresponding vertex of the curve, by using a Sample Index node. The y-coordinate of this position is the calculated Y-Displacement.