Hi Jeff, also, you wrote:

> I'm getting back to my learning project

This is actually a quite complex project that you're tackling here... It's maybe a bit like learning how to drive by jumping on the Indy 500 racetrack right away.

It can actually be particularly difficult task just in general to try and reverse engineer the structure of an object when all you have are some parts outlined at awkward angles.

That's a lot different kind of a project than one where you're more freely creating an object just according to your own desires, because you are then more free to create surfaces using simple cross sections that can then be rotated into place instead of trying to figure out how to match some projected already rotated profile.

So that's something to keep in mind, that this is just generally a difficult area that you've chewed off here.

- Michael

I guess I've never been accused of doing things the easy way....

I think what you are looking for for the armrest area, is a need to set a cplane to get the working plane at the angle you need to work with..

So you can draw a line that is perp to that crossing line for the armrest, then use it to set a cplane to that view (You can do it with a construction line while setting the cplane, but this is for illustration)

Then the front view will look staight down that angle, so you can adjust the curvature as needed:





I had a couple guys from another software asking me about guitar work, and I told them I would make a video to address a couple areas.. It will be much easier in MoI, but Maybe this weekend I will get those videos together and respond to them, and you also here... I got overwhelmed with a tournement, then my daughter broke her elbow, but it's settling down a bit now, so I'll see if I can spit something out that can help here a bit..

Thanks for responding quickly.

The curve does run roughly perpendicular to the lines as you show on in the first image.

I attached an image (render) I found that shows this. I also attached the blueprint. I could just tweak the curve until I like it, but I'm trying to learn how to tackle this type of problem.

One idea I had was to use the Isect command to intersect the lines at a plane at the cross section line to create some points there. Then snap to those points and align them to the right cross section in the the right viewport. Would that work? If I turn on points and just grab the line and shift it perpendicularly downward I think this may work.

Thanks,
Jeff

Soccer? Hope your daughter heals quickly. I guess I need to research the cplane command to fully understand what you are telling me to do.

Thanks for your post.

Update...

I understand Cplane now, but I don't think it will help. Since, as Michael mentioned, I only have the curve info at that awkward angle relative to the armrest curve. I guess if I'm not trying to reverse-engineer then it would be useful for defining my own curvature. Thanks for the tip.

Hockey...

I think that curvature there is not arbitrary, but it's an 8 inch radius.. The main thing you need to do there is to maintain tangency with the start of the curve and the flat top of the body... this is evident if you create that Cplane, then look straight on to it.. You will see that there is a hard edge there... Creating the curve, then the resulting surface to use for a boolean is needed because you wont be able to get a "complete 8 inch fillet", as that would have it be collapsing down onto itself in the very end..

So here is the curve you have, l;ooking at it from that angle and how it meets the top:



This is actually the main thing I need to show the other software users to be aware of, and requires the same thing.

If you place that second point "inline/inplane with the first when, then the resulting surface will be a smooth tangent result when cut away.



It should help in this situation too, when you want to reverse engineer it, because setting that cplane properley, will allow you to place another image right there that contains that curve, at the proper angle, to then mimic it..


Am I correct to think that this is the curve of that armrest??

Hi Jeff,

> I guess if I'm not trying to reverse-engineer then it
> would be useful for defining my own curvature.

Yup, basically setting the cplane is an way for you to draw something in place at some angled position, it can relocate all the top/front/right views temporarily so that you can work in that local position as if that angled direction were the world axis directions, including even typing in coordinates relative to that temporary origin point.

But yeah, the reverse engineering aspect with sort of semi-incomplete information (you basically don't have the "plan" for that particular sloped piece if I understand correctly) puts a lot more difficult spin on things...

- Michael

By the way Burr, bummer that your daughter broke her elbow, I hope she heals it up quickly too.

- Michael

Hi Jeff, by the way a couple of previous guitar discussion threads that you may want to check out:

http://moi3d.com/forum/index.php?webtag=MOI&msg=3618.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=2145.1

We haven't got to the filleting part of what you were asking about, but if you have something that's got tight bends in its outline and you want to have it rounded by a large amount around that tight bend, fillet may not be the best way to do that, you may instead need to kind of construct a rounded surface pieces by other means like lofting several profiles or something like that, I think that's part of those other discussions.

- Michael

"""""" I hope she heals it up quickly too."""

Thanks Michael... She should be ok. We'll be in once a week for xrays to see if it goes well. She's kindof like me with a high tolerance for pain, so the challenge is to get her to stop jumping and diving on it so it will set up!! :o (May have to tie her to a chair??)

Hi Jeff, so for your reverse engineering method, you are probably going to do the cplane method so that it is easy to draw and manipulate a cross section to make the kind of shape you want. Instead of lofting a bunch of lines to make that sloped shape (is that what you were doing before) instead just draw one side profile and make an extrusion to do it- then you can tweak just that one profile curve and the extrusion will update- that's much easier to manage for editing.

Then where you've got the vertical plane you can select your sloped extrusion, and then select that vertical plane and then run the Construct > Curve > Isect command. That command will intersect the 2 surfaces and produce a curve at their intersection, and your task will be to tweak the extrusion (by editing the profile that was extruded) until that intersection curve is the shape you need.

A couple of things that will help with this - you will want to get the 3D view to be set up with the CPlane in the plane of the extrusion curve so you can do your editing there.

But when you set your cplane up you will want to uncheck the option for repositioning the ortho top/front/right views (the options appear in the upper-right corner of the window where the options for the current command is displayed) so that the Right-side view will stay oriented along the world axis so that you'll be able to get a clear view of the intersection result.

Then the other trick is that after you do the intersection once you should select the intersection curve result and enable history updates for it by going to Edit > History and click the "Enable update" button. History updating is automatically on for extrusions, so the extrusion will automatically update when you edit its profile curve, but the intersection command does not have history updates turned on by default, so you have to turn it on with this manual step.

However, once you have turned it on then you should find the whole thing updates every time you move any control points of the original sloped extrusion piece, so you'll tweak those points in the 3D view where the cplane is at that angle, but you'll be watching the result of the history updated intersection curve in the Right-side view to see how close you are to what you're trying to get.

So like I was mentioning, you're chewing off a pretty complex task here, let me know if you get stuck on any of the things I've described here. I also did not yet do a trial run of this so I'm not 100% sure yet that I didn't miss a step or something like that.

- Michael

That's similar to my original idea in spirit. It's a lot of work to do the reverse-engineering job! I'll have to study your post carefully and give it a whirl. The benefit is getting to know more of the inner-workings of MOI. I know I can due things easier, but I think I can learn more by taking on the tougher road. Maybe I'll model some simpler/original things too to learn more basics.

Thanks guys. I appreciate the insight.

Good night.

Hi Jeff, Ok I've attached here a model file with things set up for history editing as I described above.

This is set up with an angled cplane but only in the 3D view, the top/front/right views are still oriented with the world axis.

I made a curve and extruded it to form the sloped piece, then intersected that with the vertical plane to make the magenta intersection curve. Then I enabled history updates on that magenta curve and then hid the vertical plane to kind of get it out of the way.

So now your job is to select the base curve of the extrusion which is this one:



Then adjust those control points and while you are adjusting them watch the magenta curve in the Right-side view here:



That magenta curve will show you the section that you want to have match with your blueprint.

You can adjust the points vertically in either the 3D view or the Right-side view but if you want to move them left or right you need to make that kind of adjustment in the 3D view since it has the cplane set to the same plane of the curve - remember that extrusion base curve is set at an angle and so you don't want to go move any of its control points in the ortho views other than in the world z axis direction.


Hope this helps to get your sloped piece set up properly!

- Michael

Hi Jeff,

> Maybe I'll model some simpler/original things too to learn more basics.

I'd definitely encourage that! It's kind of a more manageable way to get a head of steam up...

- Michael

An old test of sculpting guitare :)
http://moi3d.com/forum/index.php?webtag=MOI&msg=2145.1

Thanks Michael. I really appreciate all the personal attention.

BTW, I think I've found a simpler way to accomplish what I want for this project. I may set the configuration that you put together so I can learn this method too.

Here's what I did. Let me know if I'm a little crazy.

1. I drew the profile curve in the plane of the cross section.

2. I extruded this curve into a trimming surface, but set the direction parallel to the armrest slope.

3. I had to extend the curve a little to trim the entire armrest area, but I can just tweak in the right view. (I learned a bit more about the extrusion command.)





Thanks for all the help. I think I can move on to the filleting/roundover step shortly.

Jeff

Hi Jeff, yeah if that gives you the right shape then that's a great way to do it!

That will maybe have a kind of different shape to the overall sloped part than the one that has the cross section at 90 degrees though.

- Michael

I agree the 90 degree slope will be different, but I think it will capture the intent of the blueprint. The surface will pass through the curve at the cross section and that's the only info we have.

Filleting looks like it may be complicated. I'll start playing around with it after all the family goes to bed tonight.

Is there a forum link regarding how to model a screw? I need to figure out how to make some to attach the neck and pickguard.

Thanks again for all the help.

Hi Jeff,

> Is there a forum link regarding how to model a screw?
> I need to figure out how to make some to attach the neck
> and pickguard.

Well, to make the base shape you can draw a side profile and use the Construct > Revolve command.

For doing threads, see this for some links:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4140.1

But one thing to keep in mind is that screw threads pretty detailed geometry, so you do not really want to model them on things that are not going to be visible, if you were to explicitly model every little tiny feature like every screw thread it will tend to create an extremely heavy model and a very large file size.

- Michael

Thanks. I understand the heavy model issue. I'm just clueless as to how to model the screw threads so I want to learn. I'll check out the post.

I should work on the filleting issue first anyway. It seems to be a common issue for guitar modeling.