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View Full Version : How to "cut" an object with a spline?

chromecity
10-07-2007, 09:55 PM
Hi folks,

I should probably know this after all these years, but I've been modeling in several different packages lately and can't seem to figure out how to do this in Cinema.

Say I want to cut a spline pattern into the side of a capsule object. For the sake of this example, I'll use a flower spline. So I create the capsule and the flower spline and make them both editable. I can then project the spline onto the capsule's surface.

But how can I connect the two so that the spline is actually cutting into the capsule's surface, creating appropriate polygons? The "Connect" operation didn't do that for me, and I don't see any Knife options that will allow me to use a spline for knifing.

I could extrude the spline into a 3D drill object and then use boolean subtraction, but I'm wondering if there isn't a better way that just utilizes the projected spline.

There are a couple of types of solutions I'm interested in. In one case, the spline can just cut all the way through the object, essentially cutting the front and back of the capsule. Alternately, if there's a way to just stencil the spline onto one side of the object so that the polygons inside the spline area could then take on a different material, that would also be very helpful.

Thanks for your assistance...
Darter
10-07-2007, 10:46 PM
Have you tried a spline shader?
vid2k2
10-07-2007, 11:16 PM
Low Tech: extrude the flower shape and do a boolean.
Higher tech: plugins like mesh surgery , etc.
chromecity
10-07-2007, 11:22 PM
Have you tried a spline shader in the Alpha channel?
Oh yeah, the spline shader would be good for decals. I had forgotten about that. For a lot of situations, that might take care of the stenciling aspect I asked about. Thanks.

But in the instance with the current model I'm working on, I really need to actually create separate geometry. I actually have to get a decent chamfer out of the intersection of the drill and the capsule sort of curved surface object. That seems to be one of those notorous tasks that's kind of commonplace, yet very difficult to achieve decent results.
chromecity
10-07-2007, 11:28 PM
Low Tech: extrude the flower shape and do a boolean.
Higher tech: plugins like mesh surgery , etc.Low Tech - yeah, I mentioned that but was hoping for a more streamlined less artifact-causing mechanism. I thought there might be something built-in (other than regular Booleans) that would deal with imprinting a projected spline onto a surface.

High Tech - I can't remember how many versions ago Mesh Surgery stopped working, but it was quite some time now. I don't think I even have any way to run it at this point. I suppose I'd go through the trouble of getting it running in an old version if there is really a way to do this there. Are you sure there is? If not, what other plugins were you thinking of? I have about a half-zillion, so I might be set.
Per-Anders
10-07-2007, 11:46 PM
Check the scripts subforum, there's a script in there to do this.
chromecity
10-07-2007, 11:57 PM
Thanks, Per-Anders, your script looks great. :thumbsup:


And Darter, you've been holding out on me because you already knew about the script (you posted a response to it back in January). :D
Darter
10-08-2007, 12:35 AM
The Spline Cut script is great as it enables projecting and cutting with a spline as a single-click operation. Be aware though that it is an automated boole operation and as such will create the artefacts that you want to avoid.
chromecity
10-08-2007, 01:18 AM
Ah, yes, I've been seeing what you mean. Oh well, it's probably one of those cases that's just unavoidable even though intuitively it might seem that there should be some solution that works differently.
sgiff
10-08-2007, 04:56 AM
This is a great script thanks. Someone posted this in the original thread though.

"Is there any way of restricting it to a selection so that it doesn't cut all the way through the backface of a solid object.
I tried a selection and hiding but it cut right through regardless."

It works fine if you place the spline inside the object and then cut. Then it only cuts through one side and it doesn't leave a hole, it just cuts the polys, and creates NGons.

Also added a icon if you want to use it.
chromecity
10-08-2007, 01:05 PM
And Darter, you've been holding out on me because you already knew about the script (you posted a response to it back in January). :D
Okay, it seems Darter is not the only one who's been holding out on us. I seem to be very guilty of the same. When I started going through Per-Ander's script, it looked eerily familiar. Then I found some scripts I had called "Spline Etch" and "Spline Etch Projected From View". The first one had this description: "Written by Per-Anders Edwards to automate Jeff Andrews's spline-etching request." Hmmm.

A little more searching and I eventually found the thread which had actually prompted Per-Anders' script:
http://forums.cgsociety.org/showthread.php?f=47&t=452474

Doh! :rolleyes: I guess the memory is the first thing to go, eh? Well thanks again, Per.
vid2k2
10-08-2007, 01:15 PM
Other High Tech solutions would be apps that do a better job with booleans.
Though I can't point to the exact post, memory going here too, there were
threads discussing this issue. There were apps mentioned, but I hesitate to
mention one for being wrong.

All in all it does come down to booleaning no matter what method is used,
IMHO.
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