# Grooves in a cylinder

Hi everyone!

Next on my knowledge list is to do something like this…

In particular the grooves in the cylinder about half way down the page. I don’t understand this line…
This is most easily done by creating a elongated half-circle that matches the topology of the cylinder beneath it
How do you go about doing that?
Also what’s the best way to rotate and copy the groove around the cylinder?

I think I also read somewhere on my travels that there might be a better way to do this, I seem to remember the phrase, ‘simply hold ctrl and click to project the shape onto the surface’ does that help anyone?

Anyways please let me know the best way to go about achieving this, as always help is appreciated

Thanks.

That’s an U shape rotated 90 deg (orange in the first picture). You need to do a math before - how many grooves do you need (see drawing) - one segment will be cylinder divisions forming U shape + 1. That will make one segment. After you construct/draw one, erase the rest of vertices for a cylinder and using Spin or Array with Empty reconstruct cylinder, now with grooves. So, you need to know how many vertices you need on initial ring.

U shape itself is formed out of 8-point circle, centre is on one concentric loop of cylinder ( set 3d cursor there in edit mode, then switch to obj and in front ortho view create 8point circle). Next is to use Shrinkwrap Project to get that small circle points on cylinder surface. Then using Snap to points and loopcut cylinder form that U. Delete U inside faces, select edges, extrude and form groove like in picture. That is done ’ by eye’. If you need precision, additional small circle on the end of groove helps to snap needed depth.

Hope helps…

Wow, thanks eppo, I’m gonna have to buy you a drink some day

I’m sure it will help once I’ve read what you wrote a few more times, ok, many more times.

Thanks

Hope so…i mean that it’ll help a bit… however beer or two in a nice spring evening… sounds damn tempting…
Meanwhile i could try some pics or terrible video for this construction if my written is messy, guess it is.

For the barrel grooves, never underestimate the twist modifier. It would make it a breeze.

lol eppo, to be fair I haven’t tried it yet, I got distracted by this…

The 8 faced circle locked to the cylinder helped a lot, I should be able to work it out from there but I’ll let you know if I have any issues.

m910 cool, let me know how it’s done or point to a tutorial if there is one. I’ll google in the meantime.

I’m curious too. Right now can’t think how that would have to be applied… Any clues, m9105826?

Panel looks great, almost photoreal, but that oval… k.hmm, mildly put, not exactly match imho.

lol, I hear ya, I know it’s not great, that’s the bit that distracted me. I’ll get there though

Right then, lets tackle things one thing at a time

Set 3d cursor to front vertex in edit mode…

but when I switch to edit mode it moves…

ctrl alt shift c doesn’t work in edit mode.

So I carried on, ignoring the above problem and after applying the shrinkwrap I get this…

But it’s not part of the cylinder mesh yet.

Going to find some tutorials on shrink wrap…

You need Shift s - cursor to selection while in Edit mode.

Thanks swampy

Making some progress…

So, if you compare this image to the one in the tutorial it’s looking about the same. How do I get from this point to this…

Notice how the edges are sharp but the inner face is curved. “Simply extruding” like it says in the tutorial, doesn’t do it.

There’s inconsistency with what in tut pic and yours. You do have tris, while if you look at Jonathan’s there’s not. Make more divisions on circle/cylinder whatever you started with. See my post - delete faces inside groove, select edge loop and extrude that. Push it into cylinder, extrude again. Use snapping to cylinder bottom to position extrusion end vertices.

I’m only going off 2 panels instead of 4, I’d need to up the vertices in my cylinder. So how do those tris change things?

Is there a method to scale from the bottom up so that the top verts stay in line with the top rim?

And is it a case of manually putting in edges and subdividing to finish things up in the centre of the groove?

This is where I got to…

I’d still like to know the best way to scale up from the bottom. I’d also like to know how he’s done the smoothness with sharp edges, it doesn’t look like he’s got a subsurf in there but it does look like he’s ‘set smooth’.

Ok, next, array modifiers!

Array modifier went pretty smoothly…

Gr8!
Here’s why you don’t want triangles left behind in this

They should fix that

Thanks for the help