Guitar Belly Cut BooleanSplit/Parabaloid

See attached

I built out a guitar body model, but when doing the belly cut, the shape isn’t a smooth “flat” sweep across due to the way the body contours inward - the sphere of the cutout makes it look wavy.

Also notice in the model that I included the way it -should- look on a model i found - note that the shape is ‘flat’ and uniform across it’s sweep.

What is a strategy I could use to get mine even like that?

I saw a similar post on the forum but i see a similar issue in that file.

forumdemo.3dm (14.6 MB)

instead of a revolve, you could extrude the cutout shape straight/slanted:


If you want to go for a revolve cut, this can be done too, just make sure the curve you revolve is a line.

Thank you very much for the input.

I attemped the extrusion (extrudecrv / direction), but unfortunately the result is similar - still that jagged appearance. Perhaps i am not following/understanding your method exactly? Is it possible you could upload your 3DM file for me to look at? How are you determining the extrude angle?

Something else i’m trying is to start with a curve that is similarly shaped to the contour of the body and run the Pipe command, then use that to split.

That approach give me a flatter look like i want, but because of the uniform pipe shape it is removing to much material where it exits the body. Perhaps some trial and error with radius and the curve shape would yield better…

I guess I misinterpreted flat. The sample you posted showed a curved cross section while the reference has a linear (flat) cross section. What you want is a shape that keeps the width more or less the same, correct?

does this help?
I also recommend simplifying the outline curve, I did it quickly with 100 control points, but the shape can be described with a lot less points

forumdemo_sg.3dm (7.1 MB)

Unfortunately I’m on Rhino 7 and can’t open the file…

…and I know I’m doing a terrible job of describing what i’m after - easier shown than written i guess =)

thanks for your help - i’m sure I’ll eventually figure out something

@Sven_Heimdallr see attached v7 version
forumdemo_sg_v7.3dm (6.4 MB)

Beautiful! So that looks like what i’m looking for.

Just so I understand - it looks like you joined the 2 curves, then extruded as a solid right? How did you determine the angle? I presume using the direction parameter and drawing in an angled line of some sort?

And just to clarify what my issue is/was, see the screenshots below and note the red reference line - by “flat” I mean the carve looked like it was rising left to right instead of being a uniform distance from the bottom-

Mine:

Yours:

So in summary - it appears that your solution gets me what i need, i would just like to make sure i can properly duplicate it on my own.

And many, many thanks for your help!!!

If you enable History, and make a loft between the two curves, you can then see the intersection, and moving either of these two curves enables you to modify the angle.

Note that I also modified the shape of the curve to keep the width more equal.

Forgive the remedial questions (i’m very new to this), but I copied your curves, exploded them (Loft requires selecting 2 curves?), and this is the result (near the bottom - see each step i did):

what next? if i manipulate the curve(s) i get single twisted surface rather than the tubular shape you show…what did i miss? was there an extrusion step?

EDIT: did you perhaps copy the curves so that you have a duplicate “top” and “bottom” and LOFT between them?

It appears I answered my own question in the edit above - by duplicating the joined curves and lofting between them i was able to duplicate your work. I am truly grateful for your help! I have been struggling with this for quite a while now.

Bonus round: if we wanted that loft to follow a curved path instead of a straight path, would the appropriate method be to extrude the curve shapes/surface along a curve going downward? or perhaps a sweep of some kind?

you could use 3 or more sections and loft (here a loose loft is made)

forumdemo_sg__looseloft.3dm (409.1 KB)

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Sincerely, I appreciate your help i’ve been stuck a while!

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