topic Re: 3 : Projection of the selected spline/curve would result in a degenerate segment and cause future modeling problems! in Fusion API and Scripts Forum

3 : Projection of the selected spline/curve would result in a degenerate segment and cause future modeling problems!

corbin2 — Tue, 16 Dec 2025 14:38:47 GMT

Hi!

I've been plagued by this error coming up in my plugin when I'm trying to project a body into a sketch.

3 : Projection of the selected spline/curve would result in a degenerate segment and cause future modeling problems!

It works when I do it "by hand" outside of code, but doing it in code always fails.

Steps to reproduce the failure:

1. Open the attached .f3d file

2. Run the attached script (also inline below for reference).

Steps to succeed by hand:

1. Open the attached .f3d file

2. Edit the Sketch "Machining Boundary" in the component "Name Pocket"

3. P for Project, select Body, find the Body named "Inlay Body" in the component "Name Inlay".

I'm sure there is something wrong with the sketch...I wonder if there is a way I can fix it up to project correctly.

thanks,

Corbin

"""This file acts as the main module for this script.""" import traceback import adsk.core import adsk.fusion import adsk.cam from adsk.core import * from adsk.fusion import * from adsk.cam import * def log(message): userInterface = adsk.core.Application.get().userInterface userInterface.palettes.itemById('TextCommands').writeText(message) def run(_context: str): """This function is called by Fusion when the script is run.""" app = adsk.core.Application.get() try: design: Design = app.activeProduct pocketComponent = design.allComponents.itemByName('Name Pocket') inlayComponent = design.allComponents.itemByName('Name Inlay') body = inlayComponent.bRepBodies.itemByName('Inlay Body') l: list[Base] = [] inlayOcc = design.rootComponent.occurrencesByComponent(inlayComponent)[0] body = body.createForAssemblyContext(inlayOcc) l.append(body) sketch = pocketComponent.sketches.itemByName('Machining Boundary') pocketOcc = design.rootComponent.occurrencesByComponent(pocketComponent)[0] sketch = sketch.createForAssemblyContext(pocketOcc) sketch.project2(l, True) except: #pylint:disable=bare-except # Write the error message to the TEXT COMMANDS window. app.log(f'Failed:\n{traceback.format_exc()}')

Re: 3 : Projection of the selected spline/curve would result in a degenerate segment and cause future modeling problems!

BrianEkins — Tue, 16 Dec 2025 20:22:58 GMT

This looks like a bug to me, where the API isn't correctly handling the projection across components. If you put the body and the sketch in the root component, it works. I think the error message is not correct. I've made sure a bug was logged.

Re: 3 : Projection of the selected spline/curve would result in a degenerate segment and cause future modeling problems!

corbin2 — Wed, 17 Dec 2025 02:10:53 GMT

Thanks Brian!

I tried putting the body and sketch in the root component and I still get the same error.

Given the same test .f3d file, here's some code that makes it happen. I'd love to know some work around for this..

Corbin

"""This file acts as the main module for this script.""" import traceback import adsk.core import adsk.fusion import adsk.cam from adsk.core import * from adsk.fusion import * from adsk.cam import * def log(message): userInterface = adsk.core.Application.get().userInterface userInterface.palettes.itemById('TextCommands').writeText(message) def run(_context: str): """This function is called by Fusion when the script is run.""" app = adsk.core.Application.get() try: design: Design = app.activeProduct pocketComponent = design.allComponents.itemByName('Name Pocket') inlayComponent = design.allComponents.itemByName('Name Inlay') body = inlayComponent.bRepBodies.itemByName('Inlay Body') l: list[Base] = [] inlayOcc = design.rootComponent.occurrencesByComponent(inlayComponent)[0] body = body.createForAssemblyContext(inlayOcc) body = body.copyToComponent(design.rootComponent) l.append(body) sketch = design.rootComponent.sketches.add(design.rootComponent.xYConstructionPlane) sketch.project2(l, True) except: #pylint:disable=bare-except # Write the error message to the TEXT COMMANDS window. app.log(f'Failed:\n{traceback.format_exc()}')

Re: 3 : Projection of the selected spline/curve would result in a degenerate segment and cause future modeling problems!

corbin2 — Fri, 19 Dec 2025 21:31:22 GMT

I figured out a semi-workaround by extruding another set of the profiles I want in the same component; that seems to work, as long as the extrusion isn't combined with any other part.

I still can get the degenerate error to happen in other cases...but it might actually be related to bad sketches. I need to investigate and isolate it.

Corbin