Splines and control points...

[zpaolo]

I have a problem with a surface I'm trying to build: I'm modeling an electric guitar, and I'd like it to be as faithful as possible to the operative instructions passed to the people who actually build it. I have blueprints and templates, the trouble is the peculiar rounding of the body: this is a grab of the template:


As you can see there is, on the right, a perfectly flat surface, then a "rough" profile (with the polygonal profile). Usually woodworkers shape the entire profile as per the "rough" version, then smooth it down to the desired degree. I have guide curves and I can easily build the rough profile with VSS or other tools, then I'd like to create a curvature continuous spline that matches the smooth profile.

I saw that using sketcher and a (=) constraint I can obtain exactly the result I want, by tweaking the control points once the curve is in place, look at the picture:



I obtained the sketch above forcing curvature continuity and moved the control point to match the "rough outline". The trouble is that I can not "snap" the control points to the outline points, so if the profile changes, I can't easily predict the result. I can snap control points in the switch below:



but then curvature is no more continuous and the profile doesn't match the one desired...



So the question is: is there a way to snap control points AND obtain curvature continuity?

I can of course use other methods to build the surface, but I'd really like to make it this way

Thank you for your attention

Paolo

 

[Jacoolo]

if You set spline to be tangent to any kind of entity, then regarding simple spline(no extra point), Pro/e disable the possibility of control polygon. That is really sh*ty. Curvature transition do the same.

Still, instead, you can take advantage of another option which gives You a chance to change spline within plygon, unfortunately only temporaly.



You can insert extra point in the spline to obtain futher control to its flow but it will result with crazy curvature plot I think.

I am curious how do You want to handle whole surface - seems to me as 5nd boundary blend case

 

[zpaolo]

Still, instead, you can take advantage of another option which gives You a chance to change spline within plygon, unfortunately only temporaly.

You can insert extra point in the spline to obtain futher control to its flow but it will result with crazy curvature plot I think.

Yes that's right, I can control the polygons as you said, but can not "lock" them to the VSS guides, this works well if the "horizontal" and "vertical" portion of the poligonal line are fixed in length, but not if they change (as, of course, it is in my case )

As for the whole surface, I managed to build it with styling features (only a quarter of the guitar) but some transitions are really tricky so I wanted to tie them to guides. I'll keep playing with it...

 

[Jacoolo]

I suppose it is not required to address this case with ISDX(as far as my imagination of "case" are similar of what You are trying to do

)

if the "neck" of guitar fingerboard is considered, this can be achieved within ordianry tools as below





simple tangent transition achieved with conic arc

 

[dgs]

If your spline is tangent or curve continuous to a vertical line, the control line at that end will also be vertical. As far as the length, I don't think you can control the length of the control lines.

However, the nature of a spline entity is to be fluid, not to be tied to dimensions. I'd suggest that you apply a JPEG of your sketch to your model, either through the ISDX trace sketch function or applying directly to a surface, and drag your spline to match it. If you need it changed in the future, drag it again to where you need it. I think you'll save yourself a lot of frustration.

After all, the woodworkers that would make this in the past from templates wouldn't have any math behind what they are doing. They'd just file, sand and shape until it looked like the template or drawing.

 

[zpaolo]

If your spline is tangent or curve continuous to a vertical line, the control line at that end will also be vertical. As far as the length, I don't think you can control the length of the control lines.

No you can, but not together with forced curvature or tangency.

However, the nature of a spline entity is to be fluid, not to be tied to dimensions.

I know, but "fluid" does not mean "without control" I want the spline to be shaped the way I like it, this is not a free form, it just a sort of fillet.

After all, the woodworkers that would make this in the past from templates wouldn't have any math behind what they are doing. They'd just file, sand and shape until it looked like the template or drawing.

Actually in this particular model (Ibanez Radius) woodworkers shape the guitar to a rough, hard edged contour (a thing that I can easily do with VSS) and then "smooth" the edges following some templates (something I can do in WF5.0 with C2 rounds). I just wanted to do something similar with splines.

Paolo

 

[zpaolo]

Jacek, the profile I posted is part of the contour of the guitar, I managed to find a solution, adjusting splines by hand to obtain the "right" curvature and smoothness, but I have a VERY basic question again (consider that this is my first "real" attempt to build a part with lots of G2 surfaces...).

Is there a way, in ISDX, to have a "symmetric" spline? I mean I'd rather not build the section spline in half and then mirror it, I'd rather build a full spline that runs symmetricaly to the plane, but I can't find a way to adjust points on one hand and have them mirrored on the other :/

Paolo

 

[Jacoolo]

can`t say a thing because I am lacking ISDX license...

but I try to investigate the case within ordianry spline tool in sketcher/

 

[zpaolo]

can`t say a thing because I am lacking ISDX license...

Ops, sorry... Well I think I could do without ISDX too, don't know if it can be done directly in sketcher or through datum curves... actually I think that in WF5 with dynamic edit it will be as "easy" as with ISDX, gotta check it out

 

[cloughna]

How do you force curvature continuity in sketcher>?

 

[tobbo]

after you have set tangency to a spline , use the constrain "create equal lenghts" and do the same thing again and you have "C" .


//Tobias

 

[cloughna]

Many thanks Tobias.