Curve along a curve - or something like that

nikola87 · 2 Nov 2013, 20:31

hello,

I do a lot of modeling in sketchup and I really enjoy making things.. and the new problem I've stumbled upon is how to make "curve along a curve". since english is not my native language I'm not sure if I've used the right words and I have trouble googling out the soloution, so that's why I have to post yet another question here.

anyway, here it is:
I have a bezier curve that defines the slope in plane view and another that I would like to define the gradient of the slope along that path.. so it would be a slope that does not have a constant (fixed) gradient along the curvy path in the top view.

I use a lot of plugins like 1001 bit tools, curviloft etc but I just can't figure out how to do this...

thanx guys in advance

Box · 2 Nov 2013, 22:45

A simple sketch would help to understand what exactly you want.
But is it something like this?
If so, this was done with Tig's Extrusion tools. In this specific case Extrude Edges by Rails.
There will be many other ways to do what you want but we need a better idea of what it is.

nikola87 · 3 Nov 2013, 12:24

Thanx for responding.

Sorry, but that is not what I had in mind.

I've attached a sketch of the closest thing I can make with basic tools in few seconds. It's an intersection of two curved faces resulting in 3D curve. The problem is that I don't want a real intersection. I'm not sure how to explain it using correct geometrical terms so I'll explain it like this:
Imagine I've sketched a curve on wallpaper and then I stick that wallpaper on the curved wall. So, the curve on wallpaper that was drown in one plane is now ______ (I don't know the verb for this action and it's not projected since it would be a intersection) on curved surface.

So, basically I need a 3D curve, not really a face. I hope I was able to explain this now.

TIG · 3 Nov 2013, 12:37

If you make the two 'surfaces' as separate groups you can locate them cleanly without any sticking.
Them select the two and intersect-with-selection.
The new set of edges formed by the intersection will be made outside of both of the groups, and in the current context.
If you want a '3d curve' then simply select the new edges and use a 'weld' tool [e.g. TIG-weld] on them which will make them into a single curve, if possible.

Dave R · 3 Nov 2013, 12:40

It looks to me as if you are almost at what you want. Or I'm still not understanding what you want.

Make the intersection and delete what you don't need.

I see TIG beat me to it but since I went to the trouble of drawing it...

If that's still not what you want, perhaps you could post an example showing the way you would use the results you're after.

Box · 3 Nov 2013, 12:44

Or by selecting the correct control points of a bezier curve you can create any curve in 3d you want. But tig and dave's method is the most controllable.

nikola87 · 3 Nov 2013, 12:46

OK, this is really clever
Normally, I would have intersect faces and than delete the unneeded leftovers. It's great, thanks.
However, this is still not the geometry I had in mind. Please read the plastic explanation I have with wallpaper in my second post in this topic. I need the curve that is in one plane to be "rolled over" a curved surface.

I will make a new sketch soon, since my language capabilities are limited.

TIG · 3 Nov 2013, 12:52

So... are you looking to 'unfold' the form ?
A drape will 'project'.
An 'intersect' is just that

nikola87 · 3 Nov 2013, 12:58

OK.. so this is what I want to draw in Sketchup. A curve that is in vertical plane (which will later define the "not fixed" gradient of the slope, and than I want it to "I don't know the verb for this" on the curved surfaces.

Practically It would be the opposite of unfold tool.

Dave R · 3 Nov 2013, 13:04

What TIG and I showed would give you that result. If you want the ability to adjust the curve after you've made it, Box's method would work but adjusting it to exactly the way you want it would be tricky.

Box · 3 Nov 2013, 13:12

Not quite Dave, he wants a wrap rather than a projection.
If I'm reading this right, take a piece of wire and bend it into a flat curve, then bend it the other way around a former and it is different to a projection of the curve.

Dave R · 3 Nov 2013, 13:13

Then TIG's suggestion of draping would work.

Box · 3 Nov 2013, 13:15

I don't think so, as drape is a form of projection.

TIG · 3 Nov 2013, 13:16

Draping and projection are much the same as intersection, they are NOT an 'unwrapping'.
But 'unwrapping' is not the opposite of 'unfold': it's still an 'unfold'.
It's just that in this case you are starting with the edge-geometry in one single plane and then you are unfolding it so each part of the edge-geometry is made coplanar on the appropriate facet of the curved surface... it's 'wrapped'...
The complication occurs when a wrapped edge is longer than the face onto which it has just been unfolded, then it needs to be 'split' with an extra vertex added as it crosses the facet's perimeter and the wrapping continues from that point. Also you must assume that the axis of rotation of the 'wrap' for each part that is split at a facet's perimeter is the vector of that facet's edge beneath, or it the point coincides with a vertex then it's considerably more complex to decide how the 'wrap' will progress...

How about a radical alternative...
Make a flat image of the 'curve'.
Use that a texture for a material that is then applied onto the surface - you must use a UV-mapping tool to do this - 'projecting' it will bring us back to where we already are !
Now switch on hidden-geometry and manually trace new lines over the [grouped] surface, following the 'lines' in the textured surface...
The new outline is now a true 'wrapped' version of the flat form over the surface ?

nikola87 · 3 Nov 2013, 13:44

TIG,

This is exactly what I wanted to do. I guess the verb I've been looking for is "wrap". I wanted to wrap the surface with the curve as it were a texture on the curved surface.

I guess there is no easy way of doing it.. OK so, could you recommend me an UV mapping tool for this? The most challenging thing I've done with texture mapping in Sketchup is projecting so I don't know how to wrap texture on face.

Box · 3 Nov 2013, 13:45

Shape Bender will do it.

nikola87 · 3 Nov 2013, 18:05

Box,

Thanks a lot. I think that is the plugin I've been looking for.

Box · 3 Nov 2013, 18:14

Glad we got there in the end.

Shape Bender is a fantastic tool as long as you take the time to understand how to use it.

nikola87 · 3 Nov 2013, 20:10

Yes, it really is a useful tool, I'm just thinking about how much it could shorten the modelling process for me in some situations. Thanks again!