Equation curves

[garritjacobson]

Now that we have parametrics. Can we have 2D, and 3D equation driven curves like in Inventor?

I am thinking specifically of a helical gear for a small example. We could use a 2D equation curve to generate the involute, or cycloid curve of the gear tooth profile. Next we can us the 3D equation curve to generate a custom helical curve to sweep our custom 2D curve along it to cut the tooth profile. There are a great deal more applications for an equation curve of course. I just thought of the helical gear as something we could all get behind. Just think about how difficult it would be to model an accurate helical gear with an involute gear profile in Fusion as it stands. Now think of a cycloidal tooth profile. Possible...sure -difficult...YES! I haven't tried yet, but I'm guessing it would take 2 complex profiles, a loft, and a whole lot of trig. 

[Anonymous]

Is an equation driven curve function even in the works? I'm hanging onto solidworks to do my parametric equation driven curves, then importing the model.

I'm far from a pro but this seems like one of the first features a modeling software would have.

[darran]

I'm trying to model and mill a parabolic reflector as part of a project. Equation-driven curves would make this trivial but instead – and I'd love to know that there is an easier way – I'm having to fake it with a spline defined by a handful of control points whose locations are dimensioned as (x, y^2).

[dwkrider]

Sketch has a conic curve primitive.   You chose the two endpoints and rho, which for a parabola is .5

[pressturbo]

While I realize that this was suggested ages ago, As a university student, this would be the icing on the cake. It would also allow me to show my CAD professors that Fusion is the preeminent CAD software that should be taught on our campus.

[Anonymous]

Working on a Cycloidal gear - I'm a bit surprised after so many years there isn't an equation curve built-in. Fusion 360 is still useful ...but this is going to be painful.

[codereclaimers]

I built an addin to support equation-driven curves; it's just a toy right now, but I wanted to just throw it out here and see how close this is to what folks were looking for.  If you'd like to see additional features, just let me know and I'll see what I can do. I'll eventually get this up in the store once it's cleaned up and a bit more complete.

Here's the download: http://codereclaimers.com/Fusion360/EquationDrivenCurve-1.0.zip

Some example curves:

Archimedes' curveHelixCycloid

[Anonymous]

Thanks @codereclaimers, This is pretty close to what I need. But, sadly, I can't drive the equations using model/user parameters - which runs counter to (my ideal of) top-down parametric design.

This really needs to be a high(er) priority item to be considered a complete sketching environment.

[codereclaimers]

Yeah, you can use parameters in the equations, but of course the Fusion360 API doesn't provide any direct mechanism (as far as I know) to go back and update created curves after a parameter change.

I can think of one hacky workaround I can try to let the addin do updates, but I don't know if it will cause Fusion to burst into flames or not.  If I get a chance to try it out I'll post an update about it here.

[Anonymous]

@codereclaimers Oh...is there a special notation required to use parameters? when I enter one it says "unexpected token 'paramX' at position n." in the notification area. (Even a custom plugin would dictate that I'd have to manually regenerate a change.)

[codereclaimers]

Oops, sorry about that--I'm thinking about my other addin (the one for level surface meshes) that allows parameters in the equations.  I'm (still) waiting on the App Store to approve the equation curves app, and that version will allow you to use parameters in the math expressions.

[MetalDawg]

Fusion 360 will never add this feature because of what it would do to Inventor. The fact is Inventor subscriptions would suffer if equation driven curves were to be added to Fusion 360. The vast majority of what needs to be done in 90% of everything CAD'd on this planet can be done in Fusion. While Fusion isn't feature laden it has what is needed to do most of the work out there EXCEPT equation driven curves.  Adding this feature would kill Inventor. It sucks because the GUI of Fusion is so clean unlike the cluttered mess that is Inventor.

[codereclaimers]

The equation-driven curves app is now in the store (Windows-only for now): https://apps.autodesk.com/FUSION/en/Detail/Index?id=52036486659592142

If you encounter any bugs or think of some improvements you'd like, or just want to share something cool you did using the app, please email me at support@codereclaimers.com.

[anthony.a.douglas]

Thanks a millino codereclaimers, for doing that.  It needs to be publicised much better.  I looked and looked for a solution.

There is one guy high up on the google hit results that talks about writing ones own script/plugin in python with the relevant equation built right in.  I hesisitate to do that because it requires all kinds of other uncertainties and know how. oi.  high chance it won't work and I won't know why.

I was very excited to get started with fusion, and saw it as the next generation of cad, but now I am concerned that is not how the developers see it.

I am not persuaded that it is doing them any good to exclude this function.  There are many methods, such as the included script to create a sketch spline from a spreadsheet, that do allow you to make equation curves.

My own solution for the time being was simply to import a curve that I made in solidworks.  Solidworks is so full of bugs it took forever, though.  It could not compute it properly. What a joke. It is just a roots blower vane, an epicycloidal curve connected to a hypocycloidal section.

I am sure there is some way to generate a relevant dxf and import it.  My point is only that it is not hard for a pro to develop a workflow that circumvents this, if it is a deliberate restriction.

The tolerance of the curves might be a serious issue, though.  I don't know how to ensure it is high.  However I assume that any software will be making an approximation with e.g. splines using a number of points.  Some commentary on the number of points required to give a certain tolerance could simply be included with the plugin, that would be enough to solve the problem mostly.

[anthony.a.douglas]

25 bucks a year, though, Coder?  The thing is that it is such a small part of the system.  Suppose it is 1/1000 of the functionality you need.  If everyone charges as much as that, no one can afford anything.

[codereclaimers]

Hopefully over time the search engines will pick up the addin--I need to pretty up my site's description page for it, and spend some time replying to discussions in various places where people are looking for something like it.

At the moment the addin uses the smallest number of control points required to make its internal spline representation match the ideal curve to within 20 microns, but I still need to do some experimentation to verify the created Fusion360 curve matches my internal spline representation.  Once I get that ironed out, I will expose the tolerance setting to the user.

[codereclaimers]

Regarding the price: I just kind of pulled that number out of the air, because I didn't have any feel for how many people would actually have a need for the addin.  Sometimes a lot of people ask for {X}, but then you build {X} and no one actually shows up to use it.

One of the problems with creating addins with functionality that other CAD packages have, but Autodesk has chosen not to add to Fusion360, is exactly what you point out: by the time a user gets all the features they're used to having in SolidWorks or Inventor, they're paying substantially more than the base subscription price of Fusion360.

I know some folks who have decided not to port their addins to Fusion360 precisely because of this issue.  They can't lower the price enough to avoid sticker shock from Fusion users and still break even.

[MetalDawg]

Codereclaimers,

I downloaded your free trial.  If this works for me I will gladly pay the yearly subscription. You put in effort and should be rewarded for it. Too many people want stuff for free.  I am a startup business and I would pay $1200 a year for Fusion if it had all these needed functions.

[codereclaimers]

Thanks @MetalDawg!  If it's not quite up to what you need, just let me know what additional features would help.  I will continue updating the app, so anyone subscribed will have access to bug fixes and new features as they come out.

[Anonymous]

[My apologies if this is getting OT]

@codereclaimers Great job on the plugin.  I started work on my own, in python, and have what I require for this project.  The main difference is (aside from polish) I managed to implement equation saving/editing this way:

There's a generic "Attributes" interface that you can use to store data (upto 4MB!) with a spline:  When the equation editor is brought up, it searches for all splines [in the active sketch] with an attribute (by name) that is set for the equation editor version.  It then takes that list of sketches and throws them into a list box, with a default option of making a new equation/spline.

If the user selects an existing spline, it loads even more attributes (x,y,z equations, step, etc) and you can simply edit the point list for the spline, instead of regenerating.  Once the user is done, simply update the spline's attributes along with its pointlist. still needs work to maintain constraints, but it's really promising - as it means it's possible to mimic the Inventor equation interface fully:

https://help.autodesk.com/view/INVNTOR/2017/ENU/?guid=GUID-9527E927-0001-4A8F-822E-9A30064B6A8F

IMO, that would be huge (and relatively simple, for what it is). Fusion360 should already have this!!! I don't like the idea of converting my work to use the C++ API, and then having to compete for users, and dealing with maintenance - Not if I can get you in the right direction! (PM me if you need more details)  $25 yearly is more than reasonable - I'll absolutely subscribe so long as it helps me get work done.

[Luke.Hicks430]

I am currently working on a job were I need to program a curve from a specific formula that related to a cycloid. Please make this a thing. I have used other programs that had equation driven curves and it was fantastic.