Generating a Sketch from a Function

Thanks in advance for taking the time to answer the following
question:

Im not sure if this is a noobe question or not, but i have a delema, i
have a function that describes a 2-D sketch that i need to generate
for extrusion, its a relativly complex function, and i have no idea
how to "Sketch from Function"

Any help and all help would be very greatly apriciated!


Thanks in advance

Boris Drubetsky

http://websnest.com/

 

Not really sure about what You mean, but look under in the help for
"Sketch blocks" and "Create Assembly from Layout Sketch" to see if
this might help You.

// Krister

 

The closest you can get is called "curve through XYZ points" in 2007. I
think it used to be called "curve through free points", but I'm not sure
anymore. I never use it. Anyhow, this will create a curve object that is a
spline fitted to a set of input points. Those points can be read from a
text file or Excel table. The curve is not a sketch, so if you need it to
be in a sketch, you could use convert entites to copy it into a sketch.
Also, the points cannot update to anything automatically. Any changes have
to be made manually through edit feature. I'm not sure if this can be
different for different configurations. I doubt it. You'd have to create a
new curve for each config, and suppress the ones you don't need.

I believe the API can be used to generate geometry from functions, but I'm
not sure of the details, or whether you can only generate spline fits. So,
a macro, macro feature, add-in, or 3rd party tool (don't know any current
ones) will be necessary to get any significant automation. If there won't
be too many changes, some creative work with Excel and maybe design tables
could be done to at least use dimensions from the model to drive the
function without having to manually copy them.

 

Thank you very much, i will check tonight, and will update this
thread. however if anyone has any other suggestions, please do tell.

 

Unfortunately, SW has no true curve-from-function capability. The
best you can do is through points. No matter how accurate your points
are, SW connects the dots with all the finesse of a 3-year-old using
crayon.

 

Isn't that more like sidewalk chalk on a cobblestone walk

 

It's a NURBS modeler.
IF the curve can be an *exact* rational polynomial function
and not exceed the supported degree then you can be exact,
within computational limits imposed by the computer's
floating-point math.

Curves with things such as trig or log functions, as examples,
generally don't fit this as they can only be approximated by
rationals (often not very well I suspect).

 

I wrote this macro to do pretty much what you're looking for. It
automates the procedure of going from excel to Curve Thru XYZ. It's
still a spline, but you can get pretty close by increasing the number
of points. It also lets you create 3D curves in Cartesian,
cylindrical, or spherical coordinates (a la ProE). Matt Lombard's
site also has one that does 2D curves.

http://members.cox.net/takedown/FuncPlot.zip

 

THANK YOU SO MUCH!
takedown :

 

Boris,

Just because SW doesn't have a direct function for parametric curves
doesn't mean it's not doable.
But it depends what you want. There are simple geometric constructs
producing sums, squares, cubes, etc. Using these a fairly complex
expression can be produced. But again it depends what you want. It all
happens within a sketcher and it is a lot more powerful than most
users think.
Can you write out the actual function? I might be able to help you.
There are other techniques. For example, a trochoid curve cannot be
directly sketched, but still can be done a lot more precisely with a
few tricks. Making curves from X,Y,Z points is a useless technique for
mathematical curves anyway.

Regards
Attila