# Help please - stopped grooves in SketchUp?



## Eric The Viking (7 Mar 2015)

This isn't a brick-bat - I probably chose the wrong material to demonstrate it. 

It's supposed to be a stopped groove in a block of material. I'm trying to make ones like this with both ends stopped, but I've been bumping into SketchUp geometry problems, which are making it very hard.

Stopped grooves must get used in classical architecture a fair bit (fluted columns, etc.), so I was wondering if anyone had a clever (quick-ish) way to make them.

I've tried making spheres (and hemispheres), and using Follow Me to get the right shapes, but I keep falling foul of the design issue in SU that it approximates circles with polygons. So, I make a flat semicircle (in the 'ground' plane), but Follow Me on a quadrant coming vertically off the circle's edge (actually down, along and back up again) doesn't produce what I'd hoped. Here's the way I've been trying it:




The grey semicircle ought to "Follow Me" along the blue line, round the quadrant, along the straight and back up again, giving the shape outlined in black (the open semicircle end (right) shows where the lathe should finish). 

Note: when doing this exercise, I deleted the black lines above, leaving only the grey semicircle (the source profile) and the blue Follow Me path. All the lines created come from the Follow Me tool.

I think the Follow Me tool sees the two quadrants on its lathe line as a group of straight lines (part of a polygon), and it lathes the circle along them, rather than round a true arc. So the last bit isn't a tangent to the circle - you get a face pointing the wrong way, which in turn means you can't extrude it. Here's what happens:




The two faces I've put texture on seem to be created by Follow Me. The one on the left _isn't_ the original semicircle, and they aren't coplanar, nor aligned with the axes (you can see the red axis cuts through on a slant.
If I turn on "show hidden geometry" and look closely at one end, you can see the weirdness clearly:




That was with setting the number of lines in each quadrant to 48. It looks like a barge boat if it's left at the default of 6. It's almost as if the start and end of each quadrant is wrongly calculated.

It's hair-tearing at the moment, but there must be a simple way...

Heeelp, please!

E.


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## Brentingby (7 Mar 2015)

Follow Me requires that the first segment in the path be perpendicular to the profile shape. If it isn't, the profile is first projected, not rotated, to perpendicular. The same thing happens at the other end. Look through the design click build blog at finewoodworking.com. Dave Richards has done a few different posts to show how to deal with it.

By the way, increasing the number of sides in the arcs does nothing to take care of the problem. It will reduce the angle between the profile and its projection.


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## Brentingby (7 Mar 2015)

There's a post he did back in 2009 about adding details that shows the principle. There are probably others.
http://www.finewoodworking.com/item/174 ... g-details/


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## Graham Orm (7 Mar 2015)

What about creating a ball of the right diameter and sitting it in the item then intersect faces then delete the lines that you don't want.


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## Eric The Viking (7 Mar 2015)

@Brentingby: Thanks - that exactly explains the problem! I'll go search for Dave's stuff.
@Graham: Yup - tried that first as being easiest. The problem is keeping the cylindrical surface, or the spherical one.

Sorry - being a bit curt, but couldn't resist looking to see if anyone had replied, but am now leaving a trail of plaster dust over the keyboard - back to the DIY temporarily...


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## Brentingby (7 Mar 2015)

Graham's ball idea could work, too.






I used the thing I tried to describe before of making sure the profile shape is oriented perpendicular to the path. I made a ball which I then cut on its equator. After selecting the right half of the hemisphere, I used the Move tool to stretch the hemisphere into a stopped groove.


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## Eric The Viking (7 Mar 2015)

Thanks Brentingby. 

Following your prompt, I've just watched Dave Richards making a bin (drawer) pull, which is a flattened half dome.

Now you've enlightened me about the need for the path to be perpendicular where it intersects the template, it all makes sense. Dave's trick is to use a circle and rotate it ever so slightly about its centre, so that the intersection point is on the centre point of a side rather than a vertex of the polygon that substitutes for a circle. That gives you the perpendicular intersection automatically. when you've done that you can chop the circle up into quadrants and delete three of them.

I really appreciate the reply - I'd never have worked it out as there's nothing in the Follow Me help that I've come across so far (not saying it isn't there somewhere, mind).

E.

PS: Dave R has a nifty plugin for rounding over edges. I may very cautiously try getting the Ruby interpreter going later next week, when I'm feeling brave (running under Wine still).


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## Brentingby (7 Mar 2015)

I used his rotation method for my example, too. You can see that the faces around the top edge of the hemisphere and slot are narrower than the others.


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## siggy_7 (8 Mar 2015)

You could make the object in your post then copy and reflect it - would work well for objects symmetrical about their centre.


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## Eric The Viking (8 Mar 2015)

@siggy: Yup, quite agree. The big issue was all the weird artefacts from the Follow Me operation.

Basically I got hung up on trying to model some hardwood trim strips for our new built-ins (with the chimney breast between them each has a tall projecting corner to make 'tidy' ). We've got some downstairs (lounge bookcases) that are simply decorated with three stopped grooves and a roundel at top & bottom. They look simple yet elegant and it would be nice to pick up the same theme.

I've learned a lot about "SketchUp foibles" in the last 36 hours! That includes Dave Richards' thing about working on large models and scaling at the end (if I'd done that in the first place, I _might_ have twigged what was happening). 

Also smoothing. On the basis of that, I'm going to have another go at the room model itself, too. Originally I skipped bothering to detail the skirtings, picture rail, windows, etc. as although I generated the long boards with Follow Me, there were too many construction lines, so at a distance the details went 'black'. It's overdue for a re-visit.

Cheers,

E.

PS: just had a go, using the tricks discussed above. Result:




This was done by...

1. creating a follow-me line thus:
drawing a vertical "circle," 10" radius, using the standard 24 sided polygon. 
rotating it about its centre by 7.5deg. so that there's a face at the 12, 3, 6, and 9 o'clock positions.
chopping it into a filled quadrant (9 o'clock round to 6 o'clock). Aligning 9 o'clock with the model origin, coz I'm lazy. 
scaling it very slightly, so that the polygon faces at each end of the quadrant fitted to the origin and to a 10" down, red-axis-parallel guide (probably could omit this step).
making a component of it (needs more than one object, hence a filled quadrant); copying the component to the other end of the groove and flipping it; deleting unwanted geometry.
exploding it, joining the ends together to make an elongated "U" shape, making a new component, and hiding it (temporarily)

2. Drawing a horizontal circle, 10" radius, on the red axis, touching the origin, rotating that by 7.5deg. and slicing into a semicircle.

3. Paste-in-place a copy of my Follow Me line, hide the original again and explode the copy (to get the right context).

4. Do the Follow Me operation! swap inside for outside faces & delete unwanted geometry (leaves a "D" at both ends and the Follow Me lathe line). remove top face. Select All & make another component of everything. Hide component.

5. Finally, draw the solid object to be 'grooved'. Copy+paste-in-place the groove (hide the original again!). explode the groove and immediately intersect it with the solid.

Job done, and it looks pretty clean, I think. 

Thanks everyone!


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## Brentingby (8 Mar 2015)

Good work. I think you have a few unneeded steps in there, though. Still, you got it sorted.


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## Eric The Viking (8 Mar 2015)

Yup. 

Some "insurance" moves in all the components, I guess. Will get more confidence with practice...


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## Graham Orm (8 Mar 2015)

Lost me....off to do some homework.


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## Brentingby (8 Mar 2015)

From what I've gleaned from Dave over the years:





1. Draw circle. Rotate so there are sides parallel to axes.
2. Draw and quarter the circle. Delete unneeded bits. Copy to opposite end of groove. Use Flip Along to mirror copy.
3. Delete radius edges. Connect remaining arcs with a line. This is the path for Follow Me.
4. Draw semi-circle for one end of the stopped groove. It does not need to touch the path edges but it needs to be lined up correctly.
5. Select path. Get Follow Me tool. Click on semi-circle. Leave back faces showing or reverse faces so they are showing.
6. Move groove into place on board. Delete faces over groove.





Make the initial groove any length you wish. You can change the length easily by turning on Hidden Geometry. Then select the edges at one end and use the Move tool to adjust the length.


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## Shultzy (8 Mar 2015)

I've just tried this and it seems to work quite well
Draw the "lozenge" shape - 2 half circles at the end of a rectangle
Draw a square underneath at right angles to, and equal to, half the width
Draw a quadrant in the square and delete spare lines
Select the perimeter of the "lozenge"
Select "FollowMe" and click on quadrant.
Delete spare lines and surfaces as necessary.


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## Eric The Viking (9 Mar 2015)

Shultzy - I think you're winning so far for easiness!

I always tend to be too reductionist - break a problem down too much then get hung up on details. 

Of course I want a stopped groove, not to chop up spheres, etc., but you don't have to come at it from that direction, as you've just proved. Your method neatly side-steps the 'approximate geometry' issues, as they don't crop up if you start Follow Me in the middle of a straight line. I think you need to swap inside and outside faces at some point, but that's no big deal.

This all has turned out to be _really_ interesting!

Really appreciative,

E.

PS: I'd been dreading later in the month, when my eval. copy of SU Pro expires and drops down to SU Make. I can't justify a full licence. All this is very confidence-boosting though, as the biggest missing piece would be the set of Solid Tools, but it looks like you can do pretty much everything without them, just thinking it through and taking a few more steps.


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## Brentingby (9 Mar 2015)

Good for you Shultzy. That's brilliant!

I can think of cases in which that method wouldn't work correctly so it's good to know more than one method.


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## Graham Orm (9 Mar 2015)

Shultzy":1z5ggcn9 said:


> I've just tried this and it seems to work quite well
> Draw the "lozenge" shape - 2 half circles at the end of a rectangle
> Draw a square underneath at right angles to, and equal to, half the width
> Draw a quadrant in the square and delete spare lines
> ...




BRILLIANT! Even I got that one to work! Well done Shultzy.


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## Brentingby (9 Mar 2015)

Graham, did you try the other way?


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## Graham Orm (9 Mar 2015)

Yes I kept getting a raised bit as if it was tilted back.


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## Eric The Viking (9 Mar 2015)

Graham Orm":1d589e9i said:


> Yes I kept getting a raised bit as if it was tilted back.



That was the reason for the tiny rotations of the circles/arcs. Sketchup doesn't do genuine curved objects, but approximates them with polygons (flat) or polyhedra (3D). Follow-me doesn't like this, because it sees a follow-me lathe line that isn't perpendicular to the template it's using. If you do the tiny rotations, by the right amount and at the right point in the process, the problem goes away

But Schultzy's solution is way, way better than where I was starting from, and avoids the pitfalls.

E.


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## Brentingby (9 Mar 2015)

What Follow Me does is mathematically correct but is sometimes not what you expect.

As I said, there are times when you still need the method Dave Richards shows with rotating the circle by half the angle between vertices. As an example, draw a demilune table top and put an ogee profile on the curved edge.


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## Graham Orm (9 Mar 2015)

Eric The Viking":vgcxvkb3 said:


> Graham Orm":vgcxvkb3 said:
> 
> 
> > Yes I kept getting a raised bit as if it was tilted back.
> ...



I sussed that Eric and tried it, but only once. I did the rotation, but obviously not correctly.


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## Shultzy (9 Mar 2015)

Eric The Viking":bk2pooyr said:


> PS: I'd been dreading later in the month, when my eval. copy of SU Pro expires and drops down to SU Make. I can't justify a full licence. All this is very confidence-boosting though, as the biggest missing piece would be the set of Solid Tools, but it looks like you can do pretty much everything without them, just thinking it through and taking a few more steps.



Thanks for the nice comments. I still use v8 and unless you are going to use it professionally the pro version is not needed. I haven't found anything I can't do in v8.

Here is a drawing of a Rolls Royce Silver Ghost, note the seats which were very difficult to draw.


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## Graham Orm (9 Mar 2015)

Shultzy":4lwz8ird said:


> Eric The Viking":4lwz8ird said:
> 
> 
> > PS: I'd been dreading later in the month, when my eval. copy of SU Pro expires and drops down to SU Make. I can't justify a full licence. All this is very confidence-boosting though, as the biggest missing piece would be the set of Solid Tools, but it looks like you can do pretty much everything without them, just thinking it through and taking a few more steps.
> ...



Wow!


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## Eric The Viking (9 Mar 2015)

Ditto!

I'd still be using SU 8 but for it stopping working recently under Linux. So far I've had no real issues with SU 2015 (64-bit). It seems very well behaved actually. I dipped a toe into Ruby plugins yesterday, and the ones I've loaded also seem to work without issues. Ruby was one area that didn't behave well (under Wine) in the past. The only two niggles so far are that I can't get any internet-related stuff to work properly. That includes the object warehouse and direct-download/install of plugins, but neither are showstoppers. When it starts up it spawns a browser window, but doesn't go to the correct page. Again no biggie.

So I'm now catching up on a lot of things I'd put to one side - won't be doing Rolls-Royces though - the competition is way too steep!


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## Brentingby (9 Mar 2015)

Shultzy, that is a great model of the Rolls Royce. Nice work.

EtV: Do you have Internet Explorer installed? Or can you install it? SketchUp uses Internet Explorer on Windows and Safari on Mac for web dialog operations such as 3D Warehouse and Extension Warehouse. There are a number of plugins that also use web dialogs that require one or the other. And it doesn't matter what your default browser is for looking at the web. SketchUp only uses IE and Safari. They do that because those are the only browsers they can be assured are present.


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## Eric The Viking (9 Mar 2015)

Hmm. Not sure.

I'm surprised Trimble doesn't just pass something to the default browser. 

It's a while since I ran IE on a PC. I'm morally certain that SU 8 called Firefox without any problems. I had a few programmes that tried to call IE, but they usually didn't work correctly as it wasn't maintained.


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## Brentingby (9 Mar 2015)

No. I assure you, SketchUp uses only IE or Safari. They do not use your default browser if it isn't one of them. So for those using Windows or Mac, it's important to keep IE/Safari up to date even if you don't use them for browsing the Internet.


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## xy mosian (9 Mar 2015)

I do not like to disagree. However Sketchup 2015, make by now, has just accessed the on-line help via Firefox. I do have IE installed, but not used, which may account for this.
BTW brilliant work all around on the original quest of this thread.
xy


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## Brentingby (9 Mar 2015)

Online help is different from the web dialogs used to access the 3D Warehouse and Extension Warehouse.

In fact you can read about it in the Knowledge Base. Here's one entry.



> To connect to the Internet, SketchUp uses Internet Explorer even if you have a different default browser.



I'm not trying to be argumentative but it is the way it is.


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## Shultzy (9 Mar 2015)

Brentingby":2dj9nktc said:


> As an example, draw a demilune table top and put an ogee profile on the curved edge.



Brentingby, you can create the above using my method. Isn't a demilune table top just a semi-circular table top, unless I should be thinking of something else?


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## Brentingby (9 Mar 2015)

Where would you start the profile if you draw the semicircular top with the Arc tool?


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## Eric The Viking (10 Mar 2015)

Brentingby":3u6czzrw said:


> Where would you start the profile if you draw the semicircular top with the Arc tool?


That's an interesting question!
Based on what I've just learned, at some point on the main curve where the profile can be genuinely perpendicular to the line, I'd guess. 

If you use the Arc tool -- quadrants, arcs and so on -- you seem to get a vertex (corner) at each end, so using Follow Me at that point will cause the oddities I've been getting. But there's another "gotcha" too: assuming youi initiate Follow Me cleanly, the ends won't be square to the curve either (as the last sides of the curve aren't). 

So I'd guess, in order to make it work nicely, you still need to draw a circle and rotate it, then draw a chord, that exactly bisects faces of the "circle's" polygon. Once done, delete the major arc, and you have your demilune tabletop outline.

It seems to be a good rule to regard all Sketchup circles as polygons that have to be managed as such until you're done.

On which note, I have a follow-up question about smoothing but I'll start a new thread...


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## Brentingby (10 Mar 2015)

Eric The Viking":yzcmp846 said:


> If you use the Arc tool -- quadrants, arcs and so on -- you seem to get a vertex (corner) at each end, so using Follow Me at that point will cause the oddities I've been getting. But there's another "gotcha" too: assuming youi initiate Follow Me cleanly, the ends won't be square to the curve either (as the last sides of the curve aren't).



Exactly.


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## xy mosian (10 Mar 2015)

Brentingby":2avj8c99 said:


> Online help is different from the web dialogs used to access the 3D Warehouse and Extension Warehouse.
> 
> In fact you can read about it in the Knowledge Base. Here's one entry.
> 
> ...



Clearly my mistake.
I admit to not attempting to access either the 3D Warehouse or Extension Warehouse.
xy


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## Brentingby (10 Mar 2015)

No worries, sir. 

If you are using Mac and access the Knowledge Base it will substitute Safari for Internet Explorer.


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## Shultzy (11 Mar 2015)

Brentingby":362bp9qn said:


> Where would you start the profile if you draw the semicircular top with the Arc tool?



I've encountered these issues before when dealing with arcs. I think its because the "followme" tool expects the profile to be square to the first line its going to follow. This happens when its a circle but not when its an arc. I usually get around this issue is by creating an intersecting rectangle, intersect faces and remove what's not needed.


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