Hello,

I've been trying to sweep a group of circles along a path but it always seems that when the circles meet a curve I end up getting small intersections of the pipes. It's not a problem along straight paths but only on curved sections of the path. Am I using the wrong tool to prevent these intersections? The intersections decrease when I add more rails to the sweep to direct things more but never go away completely. Ideas? Thanks.

Hi OSTexo, can you please post a .3dm model file with the profile and rail curves for an example of the sweep problem?

Thanks,
- Michael

Hello,

Here is an example. When I use the two circular profiles and a single rail I get intersections between the pipes. I then tried to blend curve all three line segments to give the sweep command more information to accomplish the sweep but still am left with intersections, though to a lesser degree. I'm guessing there is something with the math of the blend curve command and/or sweep that really doesn't offset exactly so the pipes clear one another? Or am I just using the wrong tool? Thanks.

Hi OSTexo, the Blend function just doesn't have anything in it that tries to make a result that is equidistant from some other curve.

To keep the pipes in the same relationship to each other throughout, it would probably be good to use just one single path instead of 3 different paths.

One way to do that is to use the Transform > Deform > Flow command.

Start by making 3 cylinders with a line running down the middle like this, with just one path curve set up, like this:



Select just the cylinders and not the center line. Then run Transform > Deform > Flow. At the prompt to select the base curve now select the center line and for the target curve select the path, and set the "Stretch" option in the Flow command options:




To do it with sweep you'd want to use just the same one rail for all 3 sweeps, but it's a bit tricky to do that because when the profile is outside of the bounding box around the rails it will engage "auto place" mode where it moves the profile to the start point of the rail. So you would kind of need an option to turn off auto place mode to do it that way, currently there is not a separate option for that.

- Michael

For using Sweep, it should work to do 3 individual sweeps each time using this same one rail:



Select one circle, run Construct > Sweep, select the rail.

Select the next circle, run sweep again, select the same rail.

Select the last circle, run sweep again, select the same rail again.

- Michael

In Right view, you could also try Offsetting the outer curve that you've drawn, to the middle and inner positions. This gives a slightly different result to the one that Michael's last answer gives.

Martin.

Hello,

Thanks for all of the suggestions. The larger issue I'm running into at the moment is stacking the pipes into a matrix, e.g. 3x3. The rows stay pretty good in terms of clearance but the pipe stack rows end up intersecting with one another badly which is a little puzzling to me unless this just has to do with me using the wrong tool to keep things separated. Is it fair to say the blend curve tool will not keep the center rail curves equidistant from one another so the swept circle profiles will intersect? Thanks.

Hi OSTexo,

Is the attached file what you want, or does it have the intersections you're talking about? I made this by doing Construct > Offset with Mode = Through Point. The selected object was the rail that already had the blend in it. The point that I picked was on one of the straight stubs that hadn't been blended yet.

But, making the matrix of pipes straight like with Extrude and then doing curve to curve flow like Michael suggested should also work pretty well for keeping clearance between the pipes. The only problem I've had with that approach is that for really long skinny things like wires the cross section can end up out-of-round.

- Peer

Hi OSTexo,

re:
> Is it fair to say the blend curve tool will not keep the center rail curves equidistant from one another so the
> swept circle profiles will intersect?

That's correct, Blend curves generated between different curves will not be guaranteed to be equidistant from some other previously generated blend curve.

So instead of using blend multiple times the other solutions discussed above in this thread are:

- Use the same one common rail for generating all the sweeps instead of making individual rails for each sweep.

or

- Use Transform > Deform > Flow to deform a full block of pipes all at once.

or

- Use blend on one piece, and then for the other rails do a Construct > Offset on the Blend instead of making separate individual Blends.

- Michael