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compound curves, booleans, extrusion (AI, Alembic)


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Please could you help me understand, how Houdini handles the compound curves?
What about the compound curve and opposite directions of "subcurves"?
Why do I sometimes get the Cap and sometimes I dont?

I have also few problems and questions, below, regarding the imported AI or Alembic curves.

File SOP
- direct File SOP gives me a strange crack "error" (image attached)
- I have tried different U Order, it doesnt help

Hole SOP
- works for me only after the Resample SOP

- I cannot make it work, unfortunately, see the attachment please

- Also not working for me ... I have tried the Polydoctor, the Fuse, different resampling, nothing works

- extrudes even and odd subcurves in opposite directions, can it be fixed automatically?
- even if I fix those directions by hand (with the ReverseSOP), the Polyextrude doesnt create the hole

- only Extrude somehow works, if I fix directions with ReverseSOP by hand ... but I dont get the Caps


all the HIPLC and AI and ABC.zip

Edited by ikoon
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Not well, as you have discovered. The Illustrator import routine needs a lot of love. (really we need a curve re-write inside of Houdini) I doubt if the SideFX team is focused on that, however. What I do in this situation is save my AI file out as PNG using File/Export from Illustrator. Choose 300DPI to make it nice and large. Then you can use the Trace node with a small threshold to read the file. I still get a single stray edge in your shield model using this approach but it does render clean.




Edited by Atom
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Atom, thank you very much!

I just dont understand this ... after the import and the Resample SOP, there are just Houdini's Points, Vertices and Primitives ... it should not be important, if they came from AI or from Houdini. Everything should be working, but it is not.

I was just hoping to understand that "internal" logic more ... and work better with the curves.

Is that really some form of invisible internal "point virus", which I cannot detect and repair?

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Hole expects 2 closed polygons. File properly imports Bezier curves (that crack is just a visual issue), you need to convert it to polygon lines. Alembic contains open polygon lines, you need to close it with Ends node.


Curvesect works normally. Cookie expects 3D geometry and fails. Polyextrude extrudes in different directions due to opposite vertex order. Reverse node reverses that order. You can reverse automatically by using Normal tab in Group node, then pass this group to Reverse as Group parameter.

Note, that some tools operates over single primitives (Resample, Curvesect, Poly Split, Carve, etc.), but you may try to input polygon curves containing multiple primitives. Join and Convert Line nodes can convert between this kind of geometry. You can make primitives ready for Hole node by fusing two curves and joining them into single primitive.

Edited by f1480187
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F1 thank you very very much! I have fixed all the files.

Interesting: The Cookie-bypass.hiplc works when I disable the ColorSOP. Here is the preview. Everything except the Bypass flag stays the same. Why is that?



Btw I have tried the Cookie SOP with 2D Circles, in different angles, even in 45 degrees around the Y axis, and it is Substracting fine:





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Pre-Convex Geometry

When enabled, all non-planar polygons are converted into triangles. For planar polygons, they are converted into quads if point or vertex attributes exist.


That is enabled by default for Cookie. The fact that Cookie is working like Hole is surprising, but it seems they are not same, Hole is more reliable.



Edited by f1480187
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This is a pretty helpful thread.  Thank you all for the information.  I was also looking for solutions on this topic within Houdini.  

One thing that still isn't answered here however is the idea of true compound paths in Houdini on import.  For example, in C4D when you import an AI file that has multiple curve paths in it they will all come in uniquely (as they should) and you have the option to "connect & delete" them all into one path object that C4D creates for further processes.  This is done remarkably well and elegantly in C4D.  I would like the same thing to occur in Houdini for things I'm working on, eg morphing curve paths.  Is there a way to take the resulting paths generated from either an AI import or the Trace method and connect them together as one object?  Join doesn't work.  That just creates a mess.

Thanks in advance for any insight into this.

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  • 3 years later...

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