topic Re: Equation curve t in user defined parameters in Inventor Forum

Equation curve t in user defined parameters

rb — Tue, 12 Aug 2025 21:51:40 GMT

Working on some gnarly equation curves and I am trying to define phi as an user parameter.

Here is my phi: t*1rad-asin((a/r)*sin(t)

It seems like I can't enter t, as t from the equation curve feature, in a user defined parameter? t can only be referenced in the equation curve x(t) and y(t) input fields?

My already long and complicated equation, becomes even longer and more complicated when I have to input t*1rad-asin((a/r)*sin(t) at several instances rather than just phi.

The readability of the full coordinate is super poor because of this....

Or am I doing it wrong?

Re: Equation curve t in user defined parameters

johnsonshiue — Wed, 13 Aug 2025 20:02:33 GMT

Hi! Indeed, the 't' is only understood within the implicit expression of an Equation Driven Curve (EDC). It isn't accessible outside of an EDC. Also, a user parameter has to have a definite value and it cannot be a variable.

Many thanks!

Re: Equation curve t in user defined parameters

rb — Tue, 23 Sep 2025 18:36:40 GMT

hi @johnsonshiue

i have reached some problems that i can't solve within the equation curve. i need more parameters to play with...

can i generate a custom sketch line figure from vba or rather ilogic

any documentation or guidelines showing how to generate custom shapes by code

thanks

Re: Equation curve t in user defined parameters

rb — Tue, 23 Sep 2025 18:38:06 GMT

just for clarity, i have a working script in R code that works well to generate my shape, now i am looking for a way of running it directly in inventor and have it plotted straight into a 2d sketch or whoever it is done

Re: Equation curve t in user defined parameters

johnsonshiue — Tue, 23 Sep 2025 20:09:15 GMT

Hi! If I understand your request correctly, you have the equations and also the points generated by the equations. You may simply enter the equations in Equation Driven Curve command. Or you may put the point coordinates in a text file or an Excel spreadsheet (X, Y, and Z). Then use Import Points command in 2D/3D Sketch environment to import the points. A spline will be created fitting the points automatically.

Many thanks!

Re: Equation curve t in user defined parameters

rb — Tue, 23 Sep 2025 21:22:36 GMT

i think the import of xyz coordinates may work and be a good alternative

but is it possible to achieve the curve plotting from inside of inventor with ilogic or similar, meaning that i don't need to generate my coordinates outside of inventor

preferably, i would like to have my code inside of inventor and avoid an external script to generate the coordinates and import them manually by excel

Re: Equation curve t in user defined parameters

johnsonshiue — Fri, 26 Sep 2025 14:20:31 GMT

Hi! Yes, it should be doable. You may enter the equation in an iLogic rule to generate the points and fit a spline through the points. Or you may use Equation Driven Curve.

Many thanks!