Hi,

I am new to Houdini and have gone through several modeling tutorials which SideFX offer on their website. I am currently looking into modeling basic arches which, after they have been setup, can easily be adjusted.
I'm looking into turning that into an HDA for a project I have in mind.

I have been experimenting and modeled arches using three different methods: a Polyextrude, a Sweep/Skin combination and a Bend modifier.

My personal favorite is the sweep/skin method. But there is one problem with his technique I cannot seem to solve: I cannot seem to get the first and last vertex of the arch to sit flat on the ZX-plane without manually editing them. I just feel it can probably be solved in a more productive way.

Could someone point me into the right direction to solve this problem?

I attached a HIP file containing those three different methods to setup arches. Pretty self explanatory.

The sweep approach is by far the best way to go since you can edit the curves and still get a nice arch. The problem with the bottoms not lying flat on the ground plane has to do with the orientation of the segments that are being swept over the curve. With the sweep sop you need to provide a backbone that it can aim towards. In this case you need an inset version of your curve. To do this though you need to create a proper vector along which you can offset the curve. Using the polyframe sop gets you far but it's still not perfect.
In this example I used a wrangle to straighten out the normals of the first and last point so that any crossproduct will always be perpendicular to your groundplane. With the sweep sop you also don't need a skin or polycap node, the sweep can do this by itself. (2nd tab called output does this)

Another option that you didn't mention is to use the copy sop. With the copy sop you have to provide your points with orientation attributes instead of a reference curve. You need to first resample your nurbs curve to polygons or the shape won't match the sweep equivalent. Here you do need a skin and polycap node. You don't need to give the polycap node any points/edges in the group field, it can find these by itself with the default “cap all unshared edges if no group” turned on.

Great solution Doodlez. Thanks . On top of that I also found out that I do not have to use a polycap. In the skin node I turned on Keep Primitives.

Keep primitives also keeps the in-between segments which could cause bad geometry if you fuse it for some reason later. I think it's safer to just use the polycap.

Hi,

instead of using the bend modifier, you can also use a path deformer. You can find many examples of path deformers in this forum. I've created my own PathDeformer with the old VOP SOP. It is a bit overloaded with functionality, which you do not need necessarily, so I also created a simpler version with the new Attribute VOP. Just use a circle with open arc as input shape and you can use any geometry object to deform.

Thanks for the tips. Much appreciated!