CoCreate Modeling code examples: Draw sine curves and archimedean spirals in a workplane

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---++ <nop>CoCreate Modeling: Draw sine curves and spirals in a workplane

<img src="%ATTACHURL%/sineonwp.jpg" align="right" />
A user recently asked how to draw a sine curve using Lisp. Oh well;
my math is way too rusty for this, but I'll give it a try anyway.
The following code draws a sine curve on the current workplane -
it doesn't check if there is a current workplane.

The technique which this code demonstrates is how to build a
command which takes a long sequence of input coordinates.

<br clear="all" />

<pre>
;; -*-Lisp-*-
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Description:  Draw sine curve in current workplane
;; Author:       Claus Brod  
;; Language:     Lisp
;;
;; (C) Copyright 2006 Claus Brod, all rights reserved
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
(in-package :clausbrod.de)
(use-package :oli)

(defun draw-sine-curve(low high step scale)
  (let (cmd (curr low))

    ;; loop from 0 to (high-low)/step
    (dotimes (i (+ 1 (floor (/ (- high low) step))))
      (push (oli:make-gpnt2d :x i :y (* scale (sin curr))) cmd)
      (setf curr (+ curr step)))

    (push 'bspline_int cmd)
    (eval cmd)))

;; Usage example:
;;(draw-sine-curve -3.14 3.14 0.03 100)
</pre>

-- Main.ClausBrod - 24 Jan 2006

This is a trivial add-on, but for those who wonder how to use
code like the above from, say, the toolbox, here's a 
minimum-effort =sd-defdialog= wrapper for the function
=draw-sine-curve=.

<pre>
(sd-defdialog 'DRAW_SINE
   :variables
   '(
      (low :value-type :number)
      (high :value-type :number)
      (step :value-type :positive-number)
      (scale :value-type :positive-integer)
    )
    :ok-action '(sd-call-cmds (draw-sine-curve low high step scale)))
</pre>

-- Main.ClausBrod - 25 Jan 2006

<img src="%ATTACHURL%/spiralonwp.jpg" align="right" />
And here is how you would draw an [[http://en.wikipedia.org/wiki/Archimedean_spiral][Archimedean spiral]]
which follows the formula
<blockquote><i>
  r = a + b * theta
</i></blockquote>

<i>(r, theta)</i> are polar coordinates and must be converted into
cartesian coordinates for our 2D points on the workplane, but otherwise
the code is very similar to the original sine example.

Did I get the math right? I'm not sure. But anyway, the code produces
some interesting spirals! :D

<br clear="all" />
<pre>
(defun draw-archimedean-spiral(low high step &optional (a 1.0) (b 1.0))
  (let (cmd r (curr low))
    ;; loop from 0 to (high-low)/step
    (dotimes (theta (+ 1 (floor (/ (- high low) step))))
      ;; r = a + b * theta
      (setf r (+ a (* b theta)))
      (push (oli:make-gpnt2d :x (* r (cos theta)) :y (* r (sin theta))) cmd)
      (setf curr (+ curr step)))

    (push 'bspline_int cmd)
    (eval cmd)))

;; Usage examples:
;;(draw-archimedean-spiral -3.14 3.14 0.1)
;;(draw-archimedean-spiral -3.14 3.14 0.1 100 10)
</pre>

-- Main.ClausBrod - 31 Jan 2006

%COMMENT{type="below" nonotify="on"}%
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