I have used a nurbs circle to create the metal plate that is curved up at the sides. Once I got the shape I liked and set correctly to my model, I extruded it to the thickness I wanted. I tried to project a nurbs circle onto it and then trim it but it doesn't work. I am able to select the circle I'm using to project but can't pick the top of my plate; I can only select the inner (extruded) part of the plate. I need the hole on the top. It was suggested on the Buzz forum to add a skin to the plate circle but when I do this, my plates shape gets all messed up. Are you not able to project/trim onto a nurbs circle?

Hi!

The caps, that are placed at the ends of the extruded object are simple Bezier-curves. Houdini only shows them as surfaces. If you place a convert-SOP between the extrude and the project-SOP, with the following settings:
From type: Bezier curves
Convert to: NURBS surface
it should work.

Frank

FrankFirsching: I tried doing what you said and it still changed the shape of my object (plate). My plate is curved up at the sides (is that convex?) but when I convert it the plate flattens up in the middle; I lose my initial shape. I had already tried the convert Op yesterday with no luck. I am able to make a hole on one side of the plate but as I said earlier the shape is all wrong (not the way I had it initially). Is there another way I could go about to making a thin metal plate that curves up at the sides with a hole in the middle? Should I try using a box (flattened) and then apply a subd Op or something?

Based on the steps you described, I think you are doing something incorrectly. You can't project and trim a NURBS/Bezier circle on a NURBS/Bezier circle. You described your process with “extrude it to the thickness”. If you have a NURBS circle and extrude it, the product should be two bezier surfaces and one NURBS surface (the thickness). This explains why you are seeing the projection on the thickness of your plate.

I would suggest you use a NURBS grid for the top and bottom of your metal plate. Project and trim for that surface. To get the thickness you can extract(CarveSOP) the curve at the edge of the top and bottom plates and skin (skinSOP) those to together. In the end you will have one NURBS surface for the sides, and two NURBS surfaces for the top and bottom, both with trim surfaces.

I would highly recommend reading the Geometry PDF from the legacy material.

Hope that helps.
-k

I have tried it one more time, and I see what your problem is. I have created a small scene, which you can look at. It is a rather unconventional approach, but I tried to comment all I have done. You can middle-click on all SOPs, which are displayed in blue and Houdini will show a comment, I have written, at the bottom of the pop-up. Here is the scene file:
http://wwwcip.informatik.uni-erlangen.de/~sifrfirs/TrimIntoIrregular.hip [wwwcip.informatik.uni-erlangen.de]

Thanks guys for your help. I was wondering if you could project a nurbs curve onto the same; I guess not.

theKenny: I'll look into your method.

FrankFirsching: I downloaded your file and check it out later. I have to go to work now.

There is so much to keep track of here; what works with what.

Thanks guys.

FrankFirsching: I would never have thought of your method. Thanks; it's something new for me to use other times also. I think I found out what my problem was though; I think all I needed to do was add a Reverse Op after converting the nurbs circle to nurbs surface. When I tried that and fiddled with the settings, it brought the bump down to where I wanted it. (The convert op for some reason made my plate go funny). I don't know if using this reverse op in this way will cause problems later in the process (after all I am new to Houdini). There seems to be more than one way to model things.

Edit: I think the reverse does not really work for my case. I had to close my file without saving and when I tried to use the reverse Op as I did in the above explanation, it did not work. Sometimes Houdini does some weird things.

FrankFirshing: I tried making your trim sample and could not get it to work properly. I did however use a curve nurbs profile and a nurbs circle and merged them together. Then I wired the merged op into an extrude and I ended up with a shape extruded with a hole. Now, why am I getting this now? I didn't need to use your grid or project and trim etc as in your example. I wanted to post my hipnic file but can't here. I would be able to over at the 3dBuzz site if you happen to visit it.