Fusion 3d Spline

[Anita Damelio]

Im not sure if I'm not doing this right or it's just not possible in Fusion, but I can't seem to figure out how to make control point splines to be "tangent" when the end point is also the start point (closed loop). Is this not a supported feature?

In this sketch, add a construction line between the first and last control points, then add a coincident between the beginning (ending) point and the construction line. That should do it for you. You would probably have better control using a Fit Point Spline.

Okay. If I were to reposition that end point though, it would break the curvature, right? I've managed to make my spline using the fit point spline. Is this shape basically not possible with control point because its 100% curved at all points?

Why do you not try it for yourself? Because of the Coincident constrain, the beginning ending points cannot leave the construction line. You also could simply add a Parallel constrain between the first and last control point construction lines and not even sketch an extra one. The same is true for a fit point spline. The beginning and ending points automatically have an instantaneous tangent.

So when I use the control point spline, and connect my end point to my beginning point, it does not create a "automatic instantaneous tangent." It does with the Fit Point Spline which is nice, but not with the Control Point Spline which is the type I'd really prefer to use if possible.

I am able to add a parallel constraint to the first and last construction point lines as you said, which of course makes the spline tangent in this area, but now I lose the control ability to artistically modify the shape of the curve in that area.

See attached image for what I would need Fusion to do to allow me full control of the spline edits. If this isn't possible, I'll just stick with Fit Point for now

Thanks for your help btw!

Unless you get lucky, when you sketch a Control Point Spline, you will not get the same "instantaneous tangency" you get at the beginning, ending points of a Fit Point Spline without adding some sketch constraints to the beginning and ending control points. So if you have to have this condition, you will have to use the Fit Point Spline. The handles of a Fit Point Spline give you good control if you use them correctly. They will accept sketch constraints and dimensions to influence the spline.

You do have an option of right clicking on the Control Point Spline and adding a control point very close to the beginning, ending point to achieve a close "instantaneous tangency" that will still allow you to move the other control points as needed.

I really think it would be very easy to implement this feature since computing control point splines is very similar math to how subdivided mesh assets are controlled with a 3d low poly cage, essentially what the T-splines are. Do you know if there is a proper place to suggest this where it will actually get seen by devs? My 3d modeling background is in sub-d modeling in Maya for highpoly assets for video games, and working with a control point style manipulation is fantastic compared to fit, imho.

Technically, yes, but as stated above locking those two lines together (be it parallel or co-linear) now takes away the ability to manually move each point individually to control the shape which is the entire point of using a spline to create an organic shape, which in my case, is something I would like to have complete control over. The point is to keep free-form control of the spline, not lock aspects of it down and attempt to work around that constraint.

I have drawn a sketch consisting of a couple of lines and some splines creating a closed loop. I am having trouble using the offset tool. I would like an offset of 24mm inwards. My sketch is not fully constrained. I sustpect hat could be the trouble. Not sure how to fully constrain splines. I hope someone would take a look and help me out. Thanks!

Were you having trouble creating an offset in general, or having trouble selecting the whole perimeter at once for your offset? I was able to create the offset for your sketch, but I had to use the offset command twice as it didn't loop fully. I went ahead and created a screencast showing how I created the offset.

Hopefully this clears up the issue you were having and if so please feel free to mark this answer as a solution so others can benefit from this thread as well. If not, please let me know and I would be more than happy to keep helping!

Thank you James for the screencast. I am able to perform an offset as you demonstrate in two parts. What I need is to select the entire loop and offset in one go. This should allow the splines to scale correctly. What you are showing causes a problem as seen on the attached screen grab. I have zoomed to the top left corner to show how the offset is performed correctly here, but incorrectly in the top right corner where the "two part offset" becomes joined. The top right corner looses it's shape to the original.

Start a new sketch on that face and then use the project geometry command and click on the center of mass of the face. That will project the outside loop of the sketch in one click. Iw as then able to offset that projected geometry as one whole loop.

What I want to acheive is a scaled down version. I have tried scale which works great, but then when I go to edit the scaled sketch it jumps back up to the size it was before the scaling factor? Now that I am aware of the Project Sketch funtion I have come up withe the following work flow that achieves what I want:

I now have the original sketch intact and I have a scaled version that I can work with. Now when I edit the new sketch is remains at the scaled size because it is no longer a scaled sketch but a projected version of the scaled sketch that is now deleted. I'm sorry if I confused you with all of this.

1.) To address your edit about moving the projected sketch: when you create a projected sketch it creates a link referencing it to that original line. You will then need to go in and break the link in order to move it. You can do this by editing the sketch that the projection is in, then right-clicking the projected line and select "Break Link". This can be seen from the following screencast at roughly the 10-20 second mark.

2.) By deleting your construction lines, I was then able to select your spline in one-click as a whole. NOTE: This will still create the abrupt point in the top-right corner of your offset. This just has to do with the way your geometry is. You can only offset that smaller so much before that rounded edge starts converging to a point. A few suggestions I would have is to either scale the spline up (so recreate the spline smaller and then offset it bigger by 24mm). Another suggestion (and perhaps more complex method) is to view the curvature comb of the curve you have created. You will want the comb to look as gradual as possible indicating a smooth curve. This may make a smaller offset possible. You can smooth the curve out by doing a few things. The first is to delete the tangent constraints that are around the curve in the top-right corner of your spline and replace them with a smooth constraint from the sketch palette. Also you can move around the tangent lines (which I show in the screencast below) in order to try and create a smoother curvature comb.

I know #2 was a lot to take in so I created a screencast below detailing how I went about those steps. I ended up learning a lot about sketches so I thank you for coming to us with this problem! It's a learning experience for us all!

This screencast should show you how to perform all of the steps I outlined above in #2. Please note that when I was selecting my tangent handles (they were originally green and then when i clicked them they became blue and i could move them and manipulate them) I was just trying to show you that is how you do it. Please don't think that what I showed was a good final example of what your curve should look like! I was going fast to keep the screencast as short as possible

I know that was a lot of information to take in, but please feel free to ask me any more questions you have and I will try to answer them to the best of my ability. If this answered your question, please feel free to mark this answer as a solution so others can benefit from this thread as well. Also the link I'm posting below is a really good forum discussion about curvature that you may want to check out!

The circles are "curvature handles", for editing the curvature of the spline. You can de-activate the spline tangent handles, which will turn off the circle display, but that will change your spline curve, and I suspect that is not what you want. So, I guess the answer is no: there is no way to disable the circle display without affecting the curve.

You didn't notice the font of the text element displayed in the sketch does not dynamically change with your font selection? Obviously not. To see the new font, you need to select the font in the list by clicking, then open the font list again, search for the font where you left off, then select the next font - just to see how how different fonts look.

This is incredible counterintuitive. Usually, a font preview changes dynamically with the selection bar moving to the next font or your mouse pointer pointing at it. Natural behavior for quickly browsing through the fonts for selecting the right one right away.

You didn't notice the term "example" I used? This is not for actually working on a specific matter, this is for providing a quick and retraceable situation showing the ugly face of that "green circles" cluttering up the view.

Ah. Now I see. It isn't a dynamic preview. Right. I have to actually click on the font first. You're right. But, when I go to select another, the list reopens where I was. I don't have to "find" it again. So, half point for me, half point for you.

Okay, fine. I didn't find the green circles to be a distraction or hindrance of any kind. And yes, I really did it. Traced the letter R. With all splines. Watch me do it. Tell me where you think the green circles would have pissed you off. You may want to watch at 2x speed.

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