Geometry Nodes: Add option to Set Spline Cyclic node to keep shape
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Authored By

	Wannes Malfait (Wannes)
	Dec 7 2021, 3:38 PM

Description

Problem

At the moment setting a closed spline to not cyclic, creates a hole between the first and last control point.

What needs to change

Add a boolean field input to the node, called Keep Shape.
The field gets evaluated on the spline domain, just like the other inputs to the node.
If the original spline was cyclic, an extra control point is added at the position of the first control point where the field is true.

Related Objects

Mentioned In: D13566: Geometry Nodes: Add 'Keep Shape' Input to Set Spline Cyclic
Mentioned Here: T93811: Unable to create manual curve to mesh UV with spline parameter

Event Timeline

Wannes Malfait (Wannes) changed the task status from Needs Triage to Confirmed.Dec 7 2021, 3:38 PM

Wannes Malfait (Wannes) created this task.

Jacques Lucke (JacquesLucke) added a subscriber: Jacques Lucke (JacquesLucke).Dec 7 2021, 3:40 PM

Sounds good to me. The more tricky thing might be to correct the tilt. It might have to be changed on all points to keep the shape.

Johnny Matthews (guitargeek) added a subscriber: Johnny Matthews (guitargeek).Dec 7 2021, 3:41 PM

If keep shape is true and the extra point is added, does it still get set to cyclic=true as well?

Wannes Malfait (Wannes) added a comment.EditedDec 7 2021, 3:49 PM

If keep shape is true and the extra point is added, does it still get set to cyclic=true as well?

I don't think so, because one of the reasons to have this is, would be to have a spline that is not 'cyclic', but still looks closed. This is useful to get around some of the limitations there are currently for cyclic splines. (See T93811: Unable to create manual curve to mesh UV with spline parameter for example)

Paul Larson (GeorgiaPacific) added a subscriber: Paul Larson (GeorgiaPacific).Dec 8 2021, 2:56 AM

Hans Goudey (HooglyBoogly) moved this task from Backlog/Bugs to Community Tasks on the Geometry Nodes board.Dec 14 2021, 12:55 AM

Hans Goudey (HooglyBoogly) moved this task from Community Tasks to Product Backlog on the Geometry Nodes board.

Johnny Matthews (guitargeek) mentioned this in D13566: Geometry Nodes: Add 'Keep Shape' Input to Set Spline Cyclic.Dec 14 2021, 6:56 AM

Gerstmann Bradley (Bradley_G) added a subscriber: Gerstmann Bradley (Bradley_G).EditedJan 25 2022, 10:21 PM

I've made a node group in which I reconstructed a cyclic circle to be non-cyclic, and its start and end are overlapping to each other.
I think this is what this proposal of "Keep Shape" is suggesting.
But I encounter one issue when making up a torus, as there will be a gap at the end. (Figure.1)
the method currently for me to remove the gap is to increase the resolution for the top curve.
However, If we were to increase the resolution, whether to "Keep Shape" becomes no longer important. (Figure 2 & 3.)