# How to Partially Bend a Plane into a Cylinder Using Geometry Nodes in Blender 4.0

I'm currently working on a project in Blender 4.0 where I need to create procedural corn plant leaves using Geometry Nodes. My goal is to generate leaves that I can adjust in number to form a corn plant. However, I'm encountering a specific challenge.

I want to create a plane that bends at the bottom (near the z-axis base) into almost a cylinder shape, while the top part of the plane resembles the flat, tapered shape of a corn leaf.

So far, I've managed to create a basic leaf shape, but I'm struggling with the bending part. I think the solution might involve using the factor parameter to control the bend, but I'm not sure how to execute this.

How to bend one side of a plane into a half-cylinder shape, while keeping the other side flat, using Geometry Nodes. How to smoothly transition the geometry from the flat leaf shape to the curved base. Any example node setups or strategies for creating procedural leaves that can be assembled into a corn plant. Here's an example of what I'm aiming for:

And here's what I've managed to create so far:

I've watched several tutorials but haven't found one that addresses this particular need. I'm a bit stuck and would greatly appreciate any guidance or examples from the community.

Here's a sort of ad-hoc set up that involves mixing the vectors of a mesh line and mesh circle matching up their indices. Then extruding up to make the line a plane and the circle a half cylinder.

I think a better way to do it would be to use the vector rotate node and a curve line, which should be more versatile but I couldn't quite make it work (but there is definitely a way).

EDIT: a better method is to instance a curve circle at the end of a curve line whose length is equal to the circle's circumference and trim both at the same rate. Then convert both to mesh and extrude. This creates the impression that the plane is curling into the cylinder, which is presumably the desired result.

• Hello, and thank you for your response. I realize that my initial question might not have been clear enough. I've updated my original post with more detailed information about what I'm trying to achieve. With these new details, do you have any suggestions on how I can create the procedural corn plant leaves as described? Any insights or guidance would be greatly appreciated. Commented Dec 29, 2023 at 12:41

Okay so again to preface I am an intermediate user and don't take too many lessons from this because I'm sure that there is a simpler solution. But my strategy for the problem is basically to generate a single profile curve that has both a circular and a flat state in its data, then use those as instances along a curve that is the bend of the leaf.

Then you can use the Spline factor of the bend curve to control the transition from circle to flat.

But since this resets the position you need to capture the position of the instances before and then reapply those transforms (a number of places like this are where a more experienced user might come up with a simpler solution). Then you can also scale the profile curves by the original factor to create the taper of the leaf.

Finally I used Erindale's method of using a grid whose X and Y vertex count matched the point count of both the curve line that controls the leaf's bend and the curve line that sets its profile to loft all the curves into a mesh.

If you want to instance these things on a stalk as in the corn plant (and animate potentially the plant's growth) other modifications will have to be made. It may be that a simpler node set up will also be better suited to the parameterization of plant growth. But I suspect it will involve something like this - lofting a series of curves that transition between a circle and line and using the factor to control the various proportions - i.e. when the leaf is young it is more cylinder and the bend barely pulls it away from the stalk - but as it grows the plane section becomes bigger and it pulls away from the center of the stalk.