topic Re: subCurve node bug in Maya Forum

subCurve node bug

BurkhardRammner — Wed, 05 Sep 2018 14:45:05 GMT

Hi,

it looks like encountered another unfortunate bug.

This one is related to the 'subCurve' node.

As I haven't found anything on the net about weird behavior, I post it here:

When you get the sub-curve of a nurbsCurve which itself is the sub-curve of another nurbsCurve, all subCurve nodes take as a source the original nurbsCurve.

If I don't get it wrong, the subCurve node should take the direct nurbsCurve input node as a source and not the nurbsCurve which is actually not visibly connected, right?

Can anyone confirm this?

Maya file is attached.

thanks!

Re: subCurve node bug

sean.heasley — Wed, 05 Sep 2018 16:03:41 GMT

Hi @BurkhardRammner

Thanks for attaching the scene file!

I am seeing this on Maya 2018. Is that the same version you're working with? If not please let me know what version you are working with so I can update the log on this issue so our dev team can work on a fix for a future update/release of Maya.

Re: subCurve node bug

BurkhardRammner — Wed, 05 Sep 2018 16:19:20 GMT

Hi Sean,

I`m on 2018.4

thanks!

Re: subCurve node bug

BurkhardRammner — Wed, 05 Sep 2018 16:46:22 GMT

I don`t know if the subCurve bug is specific to 2018.4. Never used that node before...

However: the node only accepts parameter based min and max values.

Why is that? MFnNurbsCurve offers easy access to length based min and max values.

So Jean, why not add that functionality with an enum switch? Its really no big deal...

Re: subCurve node bug

BurkhardRammner — Wed, 05 Sep 2018 16:49:02 GMT

to be more specific: I 'hate' it to write a node for that myself ; }

Re: subCurve node bug

BurkhardRammner — Mon, 10 Sep 2018 07:55:18 GMT

Sean,

if I'm right, the subCurve node has another bug.

To be clear, actually I submit found bugs myself. But often, I`m not sure whether its really a bug or I did something wrong or understood the result wrongly. So, maybe this is the case here, but it looks like its a bug...

I attached the relevant scene and explain it:

There are two sets of connected nodes in two containers.

(yes, I hate it that the nodeEditor still cannot work with containers, so use the hypergraph here)

The node network is identical for both containers.

There is a nurbsCurve source connected to a subCurve node which feeds the result to another nurbsCurve node. Then the nurbsCurve data are modified by a rebuildCurve node and the last node is another nurbsCurve so we can see the result.

Whats different is that the source curve A has 7 CVs and source curve B has two CVs. The CVs of source curve A are NOT evenly spaced.

For both networks, a subCurve of identical length is produced. You can see that looking at 'curveAA' and 'curveBB'.

But, when another curve is created from these data using the rebuildCurve node, the resulting curves (curveAAA/curveBBB) have different length.

Sooo, doesn`t this look strange?

'curveAAA' is clearly wrong, right?

thanks for your help!

Re: subCurve node bug

BurkhardRammner — Mon, 10 Sep 2018 09:21:19 GMT

I created a workaround node for this bug myself -> simply create a new curve with the data from the subCurve output

(MFnNurbsCurve::create(...) ). Looks like the resulting curve from the subCurve node is of absolutely no use. Maybe its because of the knotDomain data (min max value) ? Maybe the fix would be to create a totally new curve inside the subCurve node and not a curve which carries the knotDomain data?!?

Re: subCurve node bug

Anonymous — Mon, 10 Sep 2018 12:37:36 GMT

There's a better solution.

Re: subCurve node bug

sean.heasley — Mon, 10 Sep 2018 15:17:27 GMT

Hi @BurkhardRammner

Thanks for adding all of that information!

I went ahead and updated the log with all of this new information so the devs can see it as they work on this issue.

Re: subCurve node bug

absoluteKelvin — Wed, 20 Oct 2021 14:58:58 GMT

The subCurve output is still a problem. ~~Whenever i deleteHistory on the output Curve~~, the curve reverts back to original instead of the result I have tested this in 2020.4

Edit: Correction. It happens when i try to duplicate the output curve from subCurve.

Re: subCurve node bug

BurkhardRammner — Wed, 20 Oct 2021 15:05:41 GMT

...its one of the many nodes the early Maya developers must have written when they were totally drunk and off earth when Steve Jobs told the press that Maya was the most complex piece of software ever.

I cannot think of another explanation for all that old garbage code inside Maya.

Re: subCurve node bug

absoluteKelvin — Thu, 21 Oct 2021 14:28:54 GMT

wait what Steve jobs said that? lol. I hope they fix this. because it would be a handy node to use for some procedural curve tool im building.

Re: subCurve node bug

BurkhardRammner — Thu, 21 Oct 2021 14:34:54 GMT

wait what Steve jobs said that?

Yep...but maybe it was him who was drunk?

Nevermind...

I hope they fix this. because it would be a handy node to use for some procedural curve tool im building.

...unless you are the CEO's nephew -> forget it : )

Re: subCurve node bug

BurkhardRammner — Wed, 27 Oct 2021 10:30:03 GMT

I have been re-visiting the scene where I had to deal with that subCurve issue...

My solution was to create a new nodeType, which takes as input the curve data from the subCurve node, internally creates a new nurbsCurve with these data, and then simply outputs the new curve to a nurbsCurve node.

That was, when you copy the nurbsCurve, it keeps its correct values.

Unfortunately, my most recent maya version is 2020 (no reason to get new updates, as nothing relevant for me gets a boost and also I don`t want to 'rent' maya!).

Maybe you find a default node which does the same as my 'postSubCurve' node...

Re: subCurve node bug

absoluteKelvin — Wed, 27 Oct 2021 17:30:31 GMT

fair point about the rent issue. But i have invested too much into maya and it so ingrained in my workflow. the indie pricing seems reasonable. off topic a bit sry. I have no experience in writing nodes, nor do i have the patience to maintain it. However do you have any workarounds that allows to get a cleaned curve out of the subCurve without getting into API?

Re: subCurve node bug

mcw0 — Wed, 07 May 2025 16:52:39 GMT

The subCurve node is useless!!! For all the previously posted reasons. The workaround is the detachCurve node. Works perfectly!

Re: subCurve node bug

absoluteKelvin — Sat, 06 Dec 2025 17:08:32 GMT

genius solutions thanks mcw0