topic Re: Loft between 3 faces / Smooth out model in Fusion Design, Validate & Document Forum

Loft between 3 faces / Smooth out model

ruben_van_lerberghe — Sun, 10 May 2020 02:25:18 GMT

Hi everyone,

This is my first project on Fusion although I have gone through tutorials and think I have a good understanding of the basics by now. It would be great if the following could be cleared up:

For the joint between the armrest, the back leg and the connection between the two armrests, I used loft. This however does not give me a smooth transition. I used Loft in other areas as well so I wonder if for this problem, I better use an other command?

And if i want to smooth out other areas of the model, is it best to convert to T-Splines ? ( modifying the same joinery after converting it does not go well)

Another issue is that when i want to shorten the back leg, the armrest goes down as well. I've tried removing constraints but this remains a problem where i can only redo the spline that makes the armrest.

A more general question, and hopefully also appropriate to ask here: Looking at the design history, did I make mistakes/create potential issues in the future. Parts of this chair need to be CNC'd so I need to get this model ready for that process as well.

Thanks in advance,

Ruben

Re: Loft between 3 faces / Smooth out model

davebYYPCU — Sun, 10 May 2020 03:35:43 GMT

Can see your file, but downloading it will be later in the day.

search for 3 way tee Joint, can be solid modelling, or surface. I would investigate a patch tangent to the 3 arms.

shorten the leg, will have to have an effect, so you would reduce dimension below the seat to maintain arm to seat distance.

Might help for the moment....

Re: Loft between 3 faces / Smooth out model

laughingcreek — Sun, 10 May 2020 04:09:14 GMT

all in all it's a good showing for your first time out. general thoughts would be

-you've referenced from a sub-component back up to the top level component, which strictly speaking isn't wrong, but I try to avoid it on more complex models because it makes things less stable and harder to debug.

-on sections you want to be straight, like the Center section of that leg, you might consider a short sweep, and then lofting to the sweep. otherwise you can end up with funkyness like this curvature-

sweeps where 3 parts come together are challenging to loft. you'll need to beak it down a little differently to get a good joint there. I noticed that none of your guide rails are tangent or better at this location. you can do that by creating the solids you want to connect to first-

create rails that re tangent to the solids, you can split the faces to get something to apply a tangent constrain to. Tyo may not need the guide rails at all. try just lofting half the cross sections together with the end conditions set to tangent or smooth, and adjusting the weight. that might be enough. if not put in the rails.-

this might also workbetter using surfaces instead of solids.

pic of first loft position

make 2 more like this

then patch the triangle gaps together.

attach is a rudimentary model using the same idea but with sweeps instead of lofts.

@ruben_van_lerberghe wrote:

Another issue is that when i want to shorten the back leg, the armrest goes down as well. I've tried removing constraints but this remains a problem where i can only redo the spline that makes the armrest.

I didn't look into this, could this be related to the back and forth referencing?

I don't think t-splines will help you out on this project. I usually use them for creating beginning geometry, not for finishing geometry.

Re: Loft between 3 faces / Smooth out model

ruben_van_lerberghe — Mon, 11 May 2020 01:40:46 GMT

Thanks already for the help !

I think I didn't explain an issue correctly. I want to shorten the back leg to then have space to make the 3-way T joint.So in order to temporarily have space I need the armrest to be disconnected from the back leg. Which does not seem to work.

Re: Loft between 3 faces / Smooth out model

davebYYPCU — Mon, 11 May 2020 02:16:41 GMT

Rear leg Path Sketch has that locked, at 650mm, edit that dimension....

But before you do that you might have to lock some spline points.

Might help....

Re: Loft between 3 faces / Smooth out model

ruben_van_lerberghe — Mon, 11 May 2020 02:24:21 GMT

Thanks so much. @laughingcreek

- can you tell me where i have done this cross-referencing ? is this because i have sketches in the top-component part that refer to the frame component part? at the end I cleaned up what i could ( giving sketches and bodies proper names, dragging bodies to a different component.) but i could not move the sketches. Do i need to start over in order to correct that ? As i mentioned, i want to get the finished version ready to be CNC'd so if that can give me issues, i'd rather start over..

- I don't really understand this part, i'm afraid. that center-section on the back leg looks to be straight. When you say straight on sections, does section refer to where the other part meets the leg and that i need 2 flat faces to come together?

- regarding the shortening of the back leg : in the top component there is the sketch ' JointArmBack' which influences the body : frameleft, under the component frame. so i should delete that sketch but how do i create a new sketch that appears under the sub component ?

- thanks for the illustration and file on the 3 part coming together.

- something i forgot, i created the half-spheres on the bottom of the legs using revolve. Is there an easier way to do that because 'my method' gives me extra work whenever i adapt the thickness of the legs.

Kind regards,

Ruben

Re: Loft between 3 faces / Smooth out model

ruben_van_lerberghe — Mon, 11 May 2020 20:33:07 GMT

@laughingcreek

I'm based in Europe so sorry that my replies take a while.

On top of all those previous questions, I also wondered how you would go about starting over?

( I was trying it just now thinking it's just simple copy and paste, but copied sketches don't appear in the same place so it seems like i need to redo a lot more ? )

Kind regards,

Ruben

Re: Loft between 3 faces / Smooth out model

ruben_van_lerberghe — Wed, 13 May 2020 01:20:54 GMT

I realise I asked a bunch of questions that I've solved by going through other forum posts.

So i started over and got to the point of the 3 way tee joint.

The file 'pipe' you attached gives me the error that it is corrupted? I'm stuck trying to split 3 circles and making those tangent rails...

I also think i did the legs the way you said ( with center sections using sweep), but i must admit i don't know why this is better.

An important adaptation I want to make ( I realised too late in this model) is having the legs on a curved path ( Sketch AlternativePathFrontLeg) I tried to drag the new Sketch back to when i made the front leg but it gets stopped on the timeline. Is there a good way to make an adaptation like that? I hope i don't have to start over again for that.

I attached a new file.

Thanks for taking an interest, I hope i'm not asking too much

Ruben

Re: Loft between 3 faces / Smooth out model

laughingcreek — Wed, 13 May 2020 02:35:38 GMT

@ruben_van_lerberghe wrote:

...An important adaptation I want to make ( I realised too late in this model) is having the legs on a curved path ( Sketch AlternativePathFrontLeg) I tried to drag the new Sketch back to when i made the front leg but it gets stopped on the timeline. Is there a good way to make an adaptation like that? ...

easy one first. the sketch AlternativePathFrontLeg has a projections from the sketch armrest. that's why you can't drag it forward anymore in the time line than that sketch. do you have "auto project on reference" checked in preferences? I prefer to leave it off and project my references manually so I don;t get accidental referances.

Re: Loft between 3 faces / Smooth out model

laughingcreek — Wed, 13 May 2020 02:37:21 GMT

here's the pipe file again. remember I used sweeps here,you'll have to use lofts, but it's the same idea

Re: Loft between 3 faces / Smooth out model

laughingcreek — Wed, 13 May 2020 03:14:28 GMT

@ruben_van_lerberghe wrote:

I also think i did the legs the way you said ( with center sections using sweep), but i must admit i don't know why this is better.

the way you did it it's not better. sweeps create more regular surfaces than lofts. you create sweeps first, and then loft to the faces of the sweep (make sure it's the face and not a sketch profile). then set the end condition to tangent or curvature.

attached is your file , rolled back to one of the legs, where I did a sweep and then lofted either end. the flat faces of the sweep are indeed flat. that will come in handy if you want to put a sketch there for joinery. you can check by trying to select a face for an offset construction plane. you can on the leg I made, you can't one the legs you made, cuz the ain't flat. there's a slight bit of curvature from lofting.

Re: Loft between 3 faces / Smooth out model

laughingcreek — Wed, 13 May 2020 03:35:08 GMT

@ruben_van_lerberghe wrote:
... I'm stuck trying to split 3 circles and making those tangent rails...

here's your file back with the three way split. I added a radius line to each of the three sketches that defined the ends. used those to split the faces. had to switch over to surface mode, lofted edges together, patched the opening, stitched it back into a body.

Re: Loft between 3 faces / Smooth out model

ruben_van_lerberghe — Thu, 14 May 2020 12:54:28 GMT

Thanks to all of you for these helpful answers.

It seems like my version of Fusion is downloaded from the app store and so i need to replace it with a version downloaded from autodesk.com . Otherwise i cannot open your files.

So if it's all right I would like to leave this topic open until I have successfully installed the updated version of Fusion 360.

Kind regards,

Ruben

Re: Loft between 3 faces / Smooth out model

ruben_van_lerberghe — Wed, 20 May 2020 14:44:16 GMT

Hello,

I understand the steps you take but in my new model this does not work. The faces of the armrest are fragmented and i'm trying to find a way to reconnect them. But I don't see where the problem lies.

The loft I want to do after splitting the face in 2 gives me an error ( i think because i need to select multiple pieces of the face to make up for one profile.)

The workaround that I used, extruding the last profile of the armrest before trying to make the joint, works. But that does not make for a clean model.

Do you see the problem in the attached file?

Kind regards,

Ruben

Re: Loft between 3 faces / Smooth out model

laughingcreek — Wed, 20 May 2020 15:20:03 GMT

I took a quick look,might have more time this evening.

the 2 sketches defining the arm are a mess.

-you have several tangent issues

-there several places where curves overlap instead of meeting endpoint to endpoint. you need to make sure the endpoints are coincident.

-there are short arc segments hidden in among the other curves.

-there is this in sketch armleg3

-I've experienced general performance issues in the past using trimmed ellipsis, there use to be bugs associated with it, and I suspect they are still problematic. I would approximate that with a fit point spline. in fact, I would do the entire profile with a continuous fit point spline and eliminate the arcs also.

Re: Loft between 3 faces / Smooth out model

TrippyLighting — Wed, 20 May 2020 16:48:05 GMT

@laughingcreek wrote:

...issues in the past using trimmed ellipsis, there use to be bugs associated with it, and I suspect they are still problematic.

Yep, still buggy in more than one aspect. I had honestly contemplated not reporting this.

Re: Loft between 3 faces / Smooth out model

ruben_van_lerberghe — Thu, 21 May 2020 02:00:01 GMT

Thank you,

Replacing the ellips with a spline did the trick.

I'm near the end now and struggle to find a good way to connect the two armrests. I put the recent file attached.

I hope it's okay that I ask these additional questions in this topic. If you prefer, I can also accept the solution and then start a new topic.

I just did a simple version where I made half a spline and then copied it and flipped it.

I want to do a more complex version but then it's hard to get the symmetry right. Can you tell me how I should do that ?

Another thing is that the joints between stretchers and legs & also between lower sweep and legs is not a good transition. I can just extrude them into the other body but that does not seem like the proper way. Is there a better way?

Also for the two splines behind the back, I need a reference so that the crest rails do not touch the back. The Project function does not solve that. The back is also not clearly visible if I do the sketch where I am supposed to do it, under the component Frame. So i first did a sketch in the top component to see where the spline was going and then copied that sketch into the subcomponent frame. Surely i must be missing something.

If the previous issues are resolved and i do some final tweaking, would that file be ready to prepare for CNC ?

Kind regards,

Ruben

Re: Loft between 3 faces / Smooth out model

laughingcreek — Thu, 21 May 2020 05:00:56 GMT

just had a few min to look at this. here's an approach to the symmetry problem with the back. I added a 3d line on the sketch "topsweepline" and changed the next plane to a plane thru 2 angles, so it would be normal to the ends of the arms. I added sketch 68 as a way to control how far off the back cushion the spline weep in the next sketch is going to be.

the next sketch, sketch 67, I put 3d lines on the center points of the arm rest ends, and then made a spline with curvature constraints. then sweeped the face along the spline.

that was long winded. just examine the model. i'll try and look some more tomorrow.

Re: Loft between 3 faces / Smooth out model

JamieGilchrist — Thu, 21 May 2020 19:15:56 GMT

Hey Ruben,

I want to sit in that chair when you finish it. 😊. Both @davebYYPCU and @laughingcreek have given you some sound approaches to handling this situation, So I don't have much to offer that hasn't already been said here. I will leave you, all of you really, a nice video from Chad Lockart, one of our Technical Sales guys who's an expert (surface) modeler. His approach to handling transitions like this is really powerful and a I would advocate as a really good best practices. Hopefully this will be helpful in solving geometry problems like the one you're trying to build.

Re: Loft between 3 faces / Smooth out model

ruben_van_lerberghe — Thu, 21 May 2020 23:34:24 GMT

Hi,

@JamieGilchrist

Thank you for the video. It's a bit above my skill level right now but as you say good practice. And thanks for the compliment 🙂

@laughingcreek I was able to follow your method to do the sweep. Thanks for that.

To make the model ready for CNC, I will study up on that and possibly open another topic.

For now I still have two issues which I hope is ok to ask before closing this topic:

- the joint areas between legs and stretchers. Is there a way to have a smooth connection by 'extruding the stretchers into the legs' and then deleting the part that goes 'inside' the leg ?

- If i wanted the spline for the final sweep not to be on a flat surface ( the construction plane) but a surface that's curving upwards - so the sweep bends up from the arm behind the back towards the middle and then goes down again to the other arm - how can i go about to get that ? Is there something like a curved construction plane ?

I'm sorry that it's taking so long to 'accept as solution' because I've been getting a lot of solutions already.

Kind regards,

Ruben