7 Replies Latest reply on Oct 22, 2007 11:01 AM by Ranga Narasimhan

    Sine curves in sketch

    Ranga Narasimhan
      Hi,

      Is it possible in SW sketch to produce a sine curve?

      thanks
        • Sine curves in sketch
          Dan Riffell
          If you're asking if you can use an equation to drive a spline, thenthe answer is no.  You need to use your equation tolocate points on a graph then plot the points in SW.  Then youwill have to use the curve through points command.

          This would be a great enhancement request.
            • Sine curves in sketch
              Mahir Abrahim
              Try this macro I wrote.  It's done well by me.
                • Sine curves in sketch
                  Ranga Narasimhan
                  Hi Mahir,

                  Thats was really great. I played little with it. Was cool.

                  Your macro can handle parametric equations very well. But do you have something for implicit (or) explicit equations like
                  y = f(x) (or) f(x,y)=0.

                  Now, if i have to use explicit/implicit eqns, first i have to convert them into parametric eqns and then use them which sometimes confuses me

                  Once again, great job done!!!

                  Thanks
                    • Sine curves in sketch
                      Mahir Abrahim
                      Thanks, Ranga. The macro won't automatically handle implicitfunctions of the form f(x,y)=c. It will only plot functions with a1 to 1 mapping in 3D space, i.e. the result of the functionevaluation must be a single point, and no two points can overlap.This boils down to only plotting curves, not surfaces (likef(x,y)=c). Also, no self-intersecting curves. However, if you havea function like x^2 + y^2 = 1, you can easily decompose itparametrically into x=2*t-1, y=sqrt(1-x^2), z=0. This would giveyou half the circle, while y=-sqrt(1-x^2) would plot the otherhalf. Another way would be r=1, th=radians(360)*t, z=0. It would benice if FuncPlot handled implicit functions, but I'm not that gooda programmer and unfortunately don't have that much free time However, keep in mind that Excel function can be used. So if youwanted to create a curve that was C0, but not C1, you could use anIF() command that gave different results for z based on the valuesof x,y,t. Anyhow... have fun.Mahir
                • Sine curves in sketch
                  John Burrill
                  If you create a helix with a pitch of 2Pi and a Radius of 1 and then project the profile view of that onto a sketch plane, would that not produce a sine wave?
                  (see attached)
                  Now, I don't know how useful it would be, but there it is.
                  John
                    • Sine curves in sketch
                      Mahir Abrahim

                       

                      Good observation, John.  Assuming SW isn't using some sortof internal spline interpolation, that's a good way to get an exactsinusoidal wave that will remain parametric in case you want tochange it later.

                      for y = A*cos(k*Theta), 0<=Theta<=L
                                 A = amplitude
                                 k = number of cycles per 2PI radians
                                 L = max angle

                      The helix parameters should be
                                 profile circle diameter = 2*A
                      and pitch & revolution
                                 p = 2PI/k
                                 n = L/p
                      or height and revolution
                                 H = height = L
                                 n = L*k/2PI
                      or height and pitch
                                 H = L
                                 p = 2PI/k


                      Mahir