Archtop guitar, real world units and import / export

* As ZooHead points out above, having tidy uv-isolines almost guarantees a smooth surface. So, when tweaking points it seems useful to minimise any angles occurring in subsequent bands of the soundboard. Sticking as close as possible to a 180° transition and avoiding any zig-zaggy isolines appears to help.
Screenshot 2020-10-21 at 08.42.25.png

* I guess that this makes sense, anyway, but I have not used lofted splines of this complexity in previous projects or experiments. Neither do I know what degree of adjustment is possible without altering the acustic performance of the instrument. :whistle: As expected, a bit time consuming, but, as I mentioned, you can check the results in real time in the editor / view port.
 
There may be no need for fiddling, I changed a few things in the Loft Object. (U= 90, V=1)
I also changed the Approximation Angle of all splines to 1.0 for max accuracy.
I changed the Extrude Creator for the sides to a Loft to match the top better.
Finally adding a Subdivision Modifier with Creases added to control hard edges where needed.

I don't know how this will work on a cnc machine but it looks like the subdiv smoothed out the anomaly.
It may get close enough so hand sanding can be used for final contouring.

335red.jpg
 

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Massive thanks to Helmut and ZooHead! It looks like I can export a CNC compliant DXF or OBJ file to allow the cutting of a mould. :)

But having bought Cheetah 3D and started learning how to use it, now I’ve really gone down the rabbit hole. Why not try out the whole guitar design in Cheetah 3D!

My latest challenge should be an easy fix. The lofted table and back of the guitar body ought to display the wood grain running vertically (or horizontally if book matched). At the moment it insists on swirling round the centre.

Do I need to use UV mapping to fix this? Or have I just made the material wrongly?

trial render 2.jpg
 
* I am not a UV guru but:
* If you have stuck to the lofted set of splines you automatically get a swirly UV mesh which then translates onto any material you apply. You will need to make the objects (ie the entire archtopped soundboard and the back individually) editable and then apply a suitable material. Experiment on a copy, of course.
* I assume that UV mapping (flat or frontal) may be useful.
* I don´t know what a subdiv modifier does to any wood grain, but you can toggle off/on the modifier and see what happens.
* I hope that somebody knowledgeable in UV mapping chimes in. I simply don´t know.

* In any case, it is pleasing to hear that you can export DFX / OBJ docs to control the numeric equipment of your friend. This would have been a quite challenging geometry. :);) Congratulations to your success!
 
Take my word for it, the SubDiv modifier will change the material.
I use the UV Mappers Flat mapping type after making the modifier editable.
 
It's actually best to create the seams before the subdiv modifier is editable, then make editable, then unwrap (and do that with a copy if you're not very used to creating uvs).

While ZooHead's word actually should be enough, he is right. Without making it editable, you'll have some distortions in Cheetah (in some other apps it's not a problem or not often).

(That said, whenever I can get away without UV-mapping, I'll choose that direction)
 
The UV Mapper doesn't need seams as it can work on selected polygons and does not need unwrapping.
I have more experience with the Mapper than the Unwrappers and Seams. And I've done very little UV painting.
 
You can't get always what you want out of the mapper (at least I couldn't), while the seams system is quite good in Cheetah (sometimes even automatic seams are enough). If you mean in-app-uv-painting, that's not Cheetah's forte (I still didn't try out how well that works in the free quixel mixer).

If you mean paint on UV maps, it's an easy way to get more detail that can't be modeled (like rust specs or just a bit of dirt ... With thousands of brushes available for your favorite paint pogram that's really something one should look into).
 
I have played with the in-app-uv-painting and it is very basic.
I did mean using paint programs, and I've been avoiding
that so far, but maybe it's time to give it a try.

I've been watching Adam Savage on YouTube build a
prop gun from the movie Hellboy called the Samaritan.

Inspired by this I started making the cylinder just to see if I could.
This might be a perfect time to try that technique to get the wear marks I'm imagining.
 
UV-Mapping is like cleaning up after cooking; certainly no fun, but it has to be done (well, actually not always). It's natural to shy away from it. Almost everybody kind of dislikes it.

But if you want to go that step further (or have to), it's a necessary evil. You can create additional detail very controlled - your scratch marks you could create with a procedural material or you could take one of those wear-and-tear-pbr-materials; with a combination of them you can get really far, and maybe that's already what you want.

To add controlled detail you have to paint it yourself, and be it just a mask with which you have control where those marks appear, you can add simple, single brush strokes which determine exactly how it will look. And of course you can paint complex materials to avoid having any visible repetitions of your bitmaps.

You can create not only diffuse but specular, bump and (with the right software) normal maps, very often very fast. But for all that you need a good uv-map and to carefully plan ahead where you'll have the seams (which isn't always a possibility with the mapper).

Even better would be painting on a mesh, which I seldom do (mostly hardware related and if so, only in Modo), but you should check out the possibilities of photoshop (if you have it) and quixel mixer (it's no substance painter for sure, but they are working on it and it's free).

For starters that's more then enough, but there are quite interesting other solutions rainging from very expensive (mari, but there is a toned down indie version and with every new release you can get a free testdrive for a month with full features (some 3 updates a year), midrange (like 3d coat, which includes sculpting) and a ton of others (armor paint is open source, but at the moment they sell the compiled app to get it financed), and on and on. That there are so many more or less specialiced programs doing this shows how important it is (as long as the uv map is flattened well, you don't have to watch out for seams because you simply overpaint them). I read that blender is also very good at this.

I look actually forward to use such things more (but not being that good at drawing, modo itself, quixel and photoshop will be good enough for me, at least for a while).
 
I reckon I’ll just have to use trial and error. I’ve saved every stage as a separate file so I can always go back. The screenshot below has a lofted front which has had a shell modifier and then made editable. Then I’ve applied a subdivision and Boolean modifiers. I’m wondering if I should apply the subdivision first...
Screenshot 2020-11-15 at 14.39.33.png


Anyway, I’m temporarily distracted by the strings which have a circle and path in location, but as soon as I apply a sweep the string itself is offset significantly. Is this dependent on the position of the circle?

Isn’t this fun!

Screenshot 2020-11-15 at 14.57.52.png
 
If the path for the string is in it's proper place, drag the
Circle.0 and Path.0 out of the Sweep in the object browser.

Then shift drag the them one at a time onto the Path.0,
and then drag them back out without the shift key.

This will move them to the same location as the Path.0.
Then reassemble the Sweep. This should get rid of the offset.
 
* As says ZooHead: Yep, location of profile and axis is relevant to where the sweep shows up.
* I would suggest that you generate a basic string in an empty .jas where everything is placed at the 0;0;0 origin and then copy / paste into the existing guitar model. Thence quintuplicate, shuffle around for E lo, A, D, G, B, E hi and adjust the spline topology as required.
* The distances start..bridge..nut should be identical and then you need a variable linear bit to the tuning pegs and the optional curly piggy tail..

* It also depends on the precision required. A bridge is not planar but cambered, nuts are not flat, either, and I also guess that strings not only differ in material but also in thickness.

* In my screen shot (bridge in the front, head stock in the rear) I have used a particle mesh on 6 selected polys of a cone. You can control any required curvature of the bridge and the nut (exaggerated in my sketch) by fiddling the parametrics.
Strings.png

* The (dummy) particle mesh, PM 3D, has 6 children, so there is a single instance of each. I have toggled off the creator of one of the strings to show the controlling points of the string (from front to rear: base, bridge, nut, peg and end).

* Much of this depends on the :sick::mad::devilish: depth of your rabbit hole. Modelling the details of the head stock, eg tuning pegs at al, gets increasingly laborious. On the other hand, modelling a guitar seems to be a project where most functions - partly unrelated - of C3D can be deployed in a single meta object.
 
* Much of this depends on the :sick::mad::devilish: depth of your rabbit hole. Modelling the details of the head stock, eg tuning pegs at al, gets increasingly laborious. On the other hand, modelling a guitar seems to be a project where most functions - partly unrelated - of C3D can be deployed in a single meta object.
Yup. I started this project just to find out if I could use C3D to generate a DXF or OBJ file at 1:1 scale to drive a CNC machine to carve a soundboard mould. With everyone’s help here, that looks like it is quite feasible. Scale and ratio appear to be accurate and the export files completely useable.

But now I realise that I can use C3D to visualise and refine all sorts of aspects of my guitar design. Tortoiseshell or Mother of Pearl binding? ƒ-holes or teardrops? Maple or mahogany? Black or nickel or silver hardware? How does it all look?

At this point, I’m quite happy to ignore (for example) the radius of a cambered fingerboard in my drawings (305mm or 254mm or flat). That’s not necessary for my visualisation, and neither is the string winding round the machine head post.

But because I’m still working to scale, i can actually input the correct diameter of each string! Simple pleasures!

I obviously need to get out more. In these strange times, that’s not going to happen, right?
 
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