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Modelling An Archtop Guitar

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  • Hello Everyone!

    Started using the c4d demo this morning so naturally I have some new-user questions...

    I want to create a model of an archtop guitar soundboard with a view to exporting it to CAM software to create toolpaths and cut with cnc.

    I was able to generate the outlines and contours for the guitar top in Adobe Illustrator and eventually figured out how to export them to C4d. The contours have been moved to their vertical position on the y-axis (hope I'm doing this right as I would have expected the z-axis to be the vertical?)

    Anyway, I think the next step is to convert these vector-curves into a surface - a nice smooth sweeping surface like on a real archtop guitar or a cello.

    After fiddling around for the past two hours, figure it's time to look for help.

    Any tips greatly appreciated!

    John,

    Ireland

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    Hi and welcome :thumbsup:

    What you do now is select all of the splines and drop them under a loftnurbs object like in the attached scene. Personally this is not how I would go about it. I would box model with a low resolution mesh which is then smoothed by a hypernurbs object.

    3DKiwi

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    Loftnurbs would look to be the obvious way to go about this from where you are now but I think there may be pitfalls. To work well I think all of your splines should have the same number of control points distributed in much the same places from one spline to the next.

    As to your intentions for this work, I'm not sure C4D is really an appropriate tool for generating cnc toolpaths, but perhaps someone with greater knowledge will correct that view.

    Why is the Y axis is 'up'? CAD apps have the X and Y axes on the ground plane with the Z axis up, but I think the clue is in the name, Cinema 4D. The normal orientation of a camera is pretty much parallel to the ground putting the X and Y on a vertical plane, so Y becomes 'up'. That's just a guess but I wondered about it too when I first came to C4D.

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    Just on CNC stuff. I used to own a CNC milling machine. C4D is fine to use for producing the models as you export your model in a format that your G-Code generating program can recognise. e.g. 3ds as it was in my case. You just need to ensure that all of your polygons are connected. A cylinder for example has the 2 caps as disconnected polygons.

    3DKiwi

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    Guest archtop
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  • Thanks for all the replies & suggestions.

    After a few hours of fiddling around, I figured Loft Nurbs was the way to go but... This produced strange results and I suspect it has something to do with the number of corresponding control points. So I'm not entirely sure which is the best approach now. I think I'll have a go at manually editing the number of points on each spline (not even sure if i'm using the correct terminology now!). Also I'll try adding one contour layer at a time under Loft Nurbs. I'll stick up a screenshot of the initial result under Loft Nurbs. If anyone is curious enough to check out the C4d file I can post...

    Thanks again! John

    John Moriarty

    - Struggling Archtop Guitar designer from Dublin, Ireland

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  • Well, I seem to be making some progress... got rid of the 'overhang' which was off-putting. I put 19 control points on each segment and made sure the direction was the same on each curve (thanks 3Dkiwi for tutorials!). Result looks 'stepped' instead of a gradual, sweeping surface - I assume there's a filter/tool for this? it is most noticeable at the top of the arch where it is flat. does anyone know how to blend all the layers together so there's no flat areas? I'm so new to this, I don't even know how to put a smiley at the end of the message...! J

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    Last time I modeled a guitar (archtop style) I box modeled the entire thing. No splines. The only downside to this method is that you have to play around with points until you get the desired contour, which takes time and patience.

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    The problem with LoftNurbs objects is the last spline creates a unsightly flat surface. Here's a 5 minute archtop guitar using box modelling techniques. This produces much smoother results and is easy to edit. I've left in some of my steps so you can get an idea of how I went about it. Hope this helps.

    3DKiwi

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    Nice modeling Nigel...

    Peace,

    Rich_Art. :)

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  • Thanks 3dKiwi,

    Wow, you're 5min archtop makes you about 2,000% more productive that me! It looks great - I'll try this approach next, once I can build the profile based on accurate reference points it should work out. Nighttime here in Dublin, so I'll get working on this tomorrow,

    cheers, John

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    Hi John

    You'll be able to this in a couple of months time once you're more familiar with C4D and box modelling. I just started with a plane and selected points then used the scale and move tools to move them around. I then deleted a few polygons for the cutaway area. Then just a matter of extruding with caps enabled and with 1 sub-division. Couple of edge loop knife cuts to sharpen up the edges then a pulled up a few polygons on the top with soft selection enabled. Sounds more complex than really is.

    Regards

    Nigel / 3DKiwi

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    I think the way Nigel suggests is ultimately going to give better results than loft nurbs.

    If you already have defined cross sections, then put them altogether on one bitmap and set that as a background image in the viewport. You can use that as a reference when pulling points into position. As you work along the body, you may find you are confused about which points to pull. A method I use when using multiple cross sections is to go to a top view, select the row of points I want to work on then use Hide Unselected. When you switch to a side view, you are sure of moving only the correct points. When you finish, use Unhide All and repeat for the next row.

    If you don't need to be exact, then try using the Brush or Magnet tools for pulling up the shape.

    As for CAD applications axes, I use Solidworks and that uses Y as up. Applications that use Z as up tend to be CAD apps that started as 2D such as Autocad. Ones that were always 3D such as Inventor, Solidworks, Catia, etc use Y as up. Most 3D CAD systems and C4D are left handed cartesian systems rotated so that Y is up. Autocad is right handed.

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