Modify a spline in a sketch

[gillesht]

I have a spline in a sketch and want to modify its curvature. I select the sketch and go in Edit mode. I don't see the points used to cerate the spline in order to modify them. Why? What can I do to see those points?

Best regards.

[jeff_strater]

The points used to create the spline should always be there.  Here is a screencast showing how to edit a spline, including fit points and tangent handles.  Is this a spline that you created yourself?  Some splines (imported geometry, or projected from a spline edged in a solid) cannot be edited this way.  Can you post a screenshot or screencast of what you are seeing?

Thanks,

Jeff Strater (Fusion development)

[gillesht]

I've joined a printscreen of my sketch with the spline. I've built the spline myself. After modifying the spline can I recalculate the Revol and the Shell to get a modified body?

Best regards.

[inchul.lee]

Hi gillesht,

You'll need to use 'Design History' to be able to edit, reorder, and review operations in the timeline.

For example, you can right-click a Revolution feature to edit the profile sketch.

You may find below articles useful in understanding Design History:

• What is design history?
• Use design history and the timeline

I hope this answers your question.

[gillesht]

If I didn't activate the Design history at the start of my model can I activate it to be able to use it? If not how can i modify the spline in my sketch?

Best regards.

[San_Escobar]

If you don't have the time line ( Design history) then just go to the feature tree > Sketch Tab > and select the geometry that you want update. 

HTH, Enjoy. 

[gillesht]

I did that, but I don't see the points on the spline to make a change to it. How can I see those points?

Best regards.

[gillesht]

I went back to try to edit my Sketch but the edit function is not visible in the dropdown menu. Any ideas why? I've attached a screen  capture.

Best regards.

[San_Escobar]

Hi gillesht

Looking at your picture what has happened there, I suppose is that you built an Interpolated Spline mainly driven by the Handles or even by Geometric Constraints. (Tangent and Curvature) PS: Curvature control for Spline in Fusion is a bit of pain, bewilderment sort of thing sometimes. 

Despite of that, it is possible to add Spline point as many as you require, I do recommend to work with less as possible to remain smoothness on your shape.

HTH. Happy Modelling.

[gillesht]

I don't want to insert points, I'd like to see the original points ans modify the spline by moving them. I don't understand why absic operation like that is so difficult to do. I think Fusion 360 still needs to be upgrated. Can't my problem be solved or not. If not I'll delete the spline and built anothet one.

Best regards.

[San_Escobar]

I agree with you Fusion need load of attention but splline I dont think is one of them. It works great!. 

If you follow the above and to simplify your answer, you can't see the original points just because you DO NOT HAVE IT. so I have shown how to add point to the spline. 🙂

As matter of fact, as mention before you definitivelly should have handles as per my previously post, the rest I assume you know how to go about.

HTH, happy modelling. 

[JamieGilchrist]

Hi gillesht,

once you're in the edit sketch command and you select your spline are the handles not visible?  If this is true can you share your design with us so we can evaluate the problem?

In the video below I've recreated your sketch and am able to manipulate the handles of the spline.  One thing to note is Fusion will infer some constraints which can make manipulating the spline handes difficult to seemingly inpossible.  If you select the handle and right click and "Deactivate tangent handle" then any constraints inferred will be removed.  I do this in the video below.

Also as a general practice when I'm editing splines I like to turn off the Grid snaps and Incremental moves under the grid settings options

This gives a lot more flexebility when manipulating splines.

hope this helps.

[gillesht]

I don't have handles and when I select the Sketch I don't see the Edit Sketch option. I've attached my sketch as a .f3d file.

Best regards.

[jeff_strater]

The reason why you do not have handles is because this curve is a projected curve.  It appears to be the result of a Project Intersect with the sketch plane.  By design, these curves are not editable.  Their geometry is driven parametrically by the intersection of the sketch plane and the body.  The magenta geometry color is what tells you that this is a projected curve.

This spline is also inside of a Base Body feature (probably from being converted from a Direct Modeling design).

To see this, you have to edit the base body:

Then you can see the sketch in the browser.  You can edit the sketch here:

You can do a "break link" on this:

However, that still does not create a fully editable spline curve.  The only spline curves which support editing by handles are those created by the user.

Hope this is pretty clear - the base body workflow here confuses things a bit.

Jeff Strater (Fusion development)

[JamieGilchrist]

Hi gillesht,

so now that Jeff was able to help you identify why you couldn't edit your "spline", thanks Jeff!, I'll show a way so you can get to the result you really want.

One of the big problems with using projected or duplicated edges is the software will add as many points as necessary to replicate the shape.  This is not exclusive to Fusion, every modeling software I've ever used does this (and I've used quite a few) and without user intervention, know how and powerful tools it's nearly impossible to get a quality curve from copied geometry; and if you have a poor quality curve that will lead to poor quality model surfaces.  I'll show you what I mean throughout this post.

Back to your design:

so I took a look at the curvature comb of your sketch and the quality of the splined shape is quite poor; this is the result of the software as mentioned above.

here is the result of that projected curve.  I can tell you from experience that there are a bunch of points underlying that curve, even though they are not visible, which is why the curvature comb is so rough.  The curve looks ok, but the quality of the curve is very poor, the best way to fix this is to build a new sketch and you get to control the number of points in your spline as well as edit your spline to make and adjust the final shape you truly want.

I redrew your sketch and applied dimensons to everything; again, this about controlling your design.  Dimensioning is not necessary, but makes editing easier especialy if you have particular parameters that your design is bounded by.

I'm referencing your orignal "spline" as a construction curve to build the new spline to.  I also added extended construction lines with a smooth constraint to the "spline", this will aid in the end conditions of your new spline matching the referenced one.

Now I've added the new spline, with just two points and snapped the handles to the extension reference construction lines, again giving an almost perfect match of the end conditions of the orginal "spline".  Adjusting the length of each spline handle you can closely approximate the orignal shape.

I worked the two point spline and was not able to get as close as I wanted to the referenced "spline", so I added an internal point and was able to get really close.

If I turn on the curvature comb of this spline and compare it to the original "spline"  you'll see a huge improvement to the quality of the curve.

vs.

 

a little bump in the comb of the new spline, but it's very smooth, some time and tweaking and you could work most of that out.  This is where striking the balance of mathematical quality in your model and your final products quality (based on materials, finshes, manufacturing process, etc.) is a judgment call on the designer.  If you are designing something with a really smooth glossy finish, like a car body, this likely will not be good enough, but if it's something that will have a matte or textured finish it may be okay.  It's really up to you to decide.

Now we have our finished profile we can revolve our shape.

One more comparison now of the original curve vs the new spline, but as it manifests itself in the models surface

This time we'll look at some zebra stripe analysis of both models

First the original.  you can really see how the poor quality curve affects the quality of the revolved surface.  The stripes are really rough; this is the direct result of modeling from a poor quality curve input.

Compared to the new spline where we controlled the curvature of the spline.  You can see that the surface quality of the revolved shape is much nicer and smoother when we start from better source geometry.

We can have a much deeper conversation about model and surface quality, I know there are a number of designers on this forum that have strong points of view about quality.  If you have not read it, I highly recomment reading Gray Hollands Periodic Table of Form, it's a really great piece on form and quality and perception of products based on the designers intangible intent and the engineers rational intent, both important and both influencing final product quality.

hope this helps.

[gillesht]

I can't find the option Toggle Curvature Display. What did I do wrong?

Best regards.

[bob_holland]

@gillesht,

Here is a link to assist in finding the Curvature Comb Analysis tool:

http://knowledge.autodesk.com/support/fusion-360/learn-explore/caas/CloudHelp/cloudhelp/ENU/Fusion-F...

Please let us know it this is not what you were looking for.

Thank you for using Fusion 360.

[JamieGilchrist]

Hi gillesht,

select the curve then right click and you should see toggle curvature option.

[gillesht]

I've joined a printscreeen of my new model zebra analysis. Not to good. Is there a way to improve the curvature of my model?

Best regards.

[JamieGilchrist]

I'd need to take a look at the model to see where the challenge is stemming from. would it be possible to share the model with me? you can email me directly at <jamie.gilchrist@autodesk.com>