Slicing meshes into groups with curves

[axalon]

Hi everyone,

Was wondering if you guys could give me some advice on what the best way to slice up a 3D mesh with curves would be so the result would look similar to this voronoi fracture, except with custom hand-drawn shapes.

I've seen some examples on 2D surfaces but wasn't sure how to go about it on a 3D surface

Edited May 21, 2016 by axalon

[f1480187]

Update to 15.5, then use a new PolySplit node. It is not flaweless at this moment, but may work well for you.

 

new_polysplit.hipnc

[axalon]

That looks great, but I'm looking for more of a hand carved look. Quick mockup:

Draw Curve on Sphere and pipe into PolySplit

sphere_curve.hip

[f1480187]

Your scene works well for me, if I understand you correctly. Use Edge Cusp node to split resulting edge group.

Edited May 24, 2016 by f1480187

[axalon]

Ah, wonderful, thank you!

Are there any other options outside of DrawCurve for drawing curves on geo? I tried the Curve SOP but wasn't able to get it to project. Freehand control is nice from DrawCurve, but it'd be great to be able to modify the curve after to make it a bit more tidy.

[f1480187]

Use Resample node after drawing a curve to make it more tidy. Curve SOP accepts snapping input, but I don't know why it exists, maybe it is just an old stuff. Turn on point or primitive snapping on left viewport panel and set template or selectable template flag on geometry. Curve will snap properly.

Edited May 24, 2016 by f1480187

[axalon]

Cool, the curve looks great...but now getting a "Input Projection must contain only one curve" error? Geometry not cooked?

sphere_curve.hip

[f1480187]

There is another error message in your scene file for me on 15.5.480: it requires polygon line primitive, not NURBS curve. Simply use resample to do such conversion. For the one curve at a time limitation, see my first example file how to do splits per primitive in foreach loop.

[axalon]

Thanks for the help f14! Finally got a chance to get back into this and am happily using curves to slice away. My issue is in merging everything into a group for control over all cut out elements.

In your above example you used a ForEach to cycle through all the sliced elements. I'm wondering if this is possible because you used a platonic to cut things up? Unfortunately I'm not seeing how to group together all these curves into one group node. I tried setting up the foreach node as you did in your first example but it doesn't look like I can just pipe in all the curves into the foreach element.

I've attached my progress, hopefully it's something simple I'm missing.

P.S. How can I hide the original mesh? Because I'm using a merge node at the end to group everything together the mesh isn't keeping track of all the cut out pieces.

curve_work_1_1.hipnc

[f1480187]

You need to manage groups in foreach and also it seems, that we need to specify piece block path. It's strange that it worked in first scene without it.

curve_work.hipnc

[axalon]

Is it possible to use an Attribute VOP to apply transformations to the cut up pieces or do I have to use a foreach SOP?

[f1480187]

It is possible to do in several ways, depending on your case. You should use for each loop to transform anything on per-piece basis. It is most convenient, in general.

[axalon]

The effect I'm going for is something like this: https://gfycat.com/AgitatedMedicalIrishredandwhitesetter

 

Displace coupled with some type of rotation. Maybe add in some RBD later on. The above example was done with the Attribute VOP, the rotation calculation direction involved calculating cross product and using quaternions. Can this be achieved with a for loop though? Feels like you'd get a lot more leverage using an attribute vop...I'm a little ignorant on how to use an attribute vop over groups like the ones generated by the polysplit node.

[LaidlawFX]

Thank you for this.

[abs0luteKelvin]

Im trying to follow this in H17. I notice the group nodes look a bit different. Im having issues with the edge split node where the whole mesh disappears?