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How to constrain a sketch/fit point spline to a 2D plane so it doesn't become a 3D sketch

Message 1 of 8
706 Views, 7 Replies

How to constrain a sketch/fit point spline to a 2D plane so it doesn't become a 3D sketch

Hello, I've been trying to trace out a mesh I converted into a Brep for a while now but Fusion keeps making my fit point splines into 3D sketches because the mesh is obviously imperfect and none of the points I want to trace are on the same plane. And when a 3D sketch/spline is created, it does not want to become a face and is basically useless.


I managed to trace out some parts of the model but i just can't do it for the part from the attached image.

Every time I want to trace a fit point spline based on the shown vertices, it creates a 3D sketch/spline that I cannot use to extrude/loft a body.

Is there a way to constrain my sketch to 2D and make Fusion project the vertices from whatever plane they are on to my sketch plane so that my sketch and spline stay 2D and I can loft them later on?

Labels (3)
Message 2 of 8
in reply to: zifcani


maybe this helps:

disable sketch.png

> then use Project tool



Message 3 of 8
in reply to: zifcani

Are you using mesh section sketches? They are planer and are able to be traced. 

Message 4 of 8
in reply to: wmhazzard

I have actually never heard about mesh section sketches but they seem like the exact thing I need. Thank you so much! I will try using them later today.

Message 5 of 8
in reply to: zifcani


Message 6 of 8
in reply to: thuffam

If you have part of the sketch wandering in Z or snapping to a mesh point, 

then you are not using Mesh Section Sketch.


Might help…

Message 7 of 8
in reply to: thuffam

@thuffam wrote:

I am having a similar issue - I need my spline to stay in a 2D plane.. but every time I try to adjust it, the points seem to wander off into 3D.  I have the option "3D Sketch" turned off (unchecked) and the preference "Design - Allow 3D sketching of lines and splines" also turned off.

Is this a bug with Fusion?  It means I cannot use it to create a simple spline and extrude it.  Surely this is the most simple thing to do.. but it is not adhering to it's settings.

This is not a bug.  Those options (they are the same option) only apply when creating new geometry (lines and splines).  That does not prevent you from using Move to drag a point or curve away from the sketch plane.  If you drag along the Z axis during move, points or curves will move away from the sketch plane, regardless of the 3D sketch setting.  You will need to be careful to only move within the sketch plane when using Move.

Jeff Strater
Engineering Director
Message 8 of 8
in reply to: davebYYPCU

Thanks. Just googling what mesh sketches are... i dont think thats what i
need. Other than the extrude of the sketch i don't have any meshes.
I just have a regular sketch on the vertical plane and it was extruded but
now I'm trying to modify the spline it will no longer do the extrude.

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