Re: LOGO-L> ellipse

[rimpey@netspace.net.au (Richard Impey)]

>Date: Fri, 13 Feb 1998 21:40:57 +1100
>To:George Mills <mills@softronix.com>
>From:rimpey@netspace.net.au (Richard Impey)
>Subject:Re: LOGO-L> ellipse
>Cc:logo-l@gsn.org	jeffr@mugc.cc.monash.edu.au
>
>Unfortunately I couldn't get either George's or Jeff's  ellipses working
>with MicroWorlds v2 for the Mac.
>I tried different combinations of values for 'rad_x' and 'rad_y' but had
>the same error messages.
>
>George's.....
>
>In the command centre I entered.........
>
>                        ellipse1 40 40
>
>and the error message was.......
>
>                        I don't know how to repcount- in ellipse1
>
>Jeff's.......
>
>In the command centre I entered.........
>
>                        ellipse 20 40
>
>and the error message was.......
>
>                        size*:eccentricity has no value in ellipse
>
>
>xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
>Georges procedure follows.....
>
>to ellipse :rad_x :rad_y
>>;
>>; There are several methods to describing an ellipse,
>>; this is just one of them and I prefer it because
>>; it's easy to conceptualize its size and calculate
>>; points that are exactly tangent.
>>;
>>; However, this is probably not the best method for
>>; describing elliptical trajectories.
>>;
>>make "orig_x first pos               ; Save current turtle pos x
>>make "orig_y last  pos               ; Save current turtle pos y
>>pu                                   ; Get to first point on ellipse
>>                                     ;   without drawing
>>repeat 361                           ; Sweep through 0 - 360 ~
>>   [
>>   make "ang repcount-1              ; For clarity create an
>>intermediate
>>                                     ;   variable
>>   make "x :orig_x-(sin :ang)*:rad_x ; Calculate New X coord
>>   make "y :orig_y-(cos :ang)*:rad_y ; Calculate New Y coord
>>   if :ang = 1 [pd]                  ; If we are already on the ellipse
>>                                     ;   then put the pen down
>>   setxy :x :y                       ; Draw a line segment
>>   ]
>>pu                                   ; Pen up for the trip back to the
>>                                     ; center of the ellipse
>>setxy :orig_x :orig_y                ; Restore original pos
>>; I'll leave it as an excercise to allow the ellipse to be rotated
>>; according to the turtles heading as MSWLogo's ellipse does
>>end
>>
>xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
>Jeff's procedure is as follows...
>
>to ellipse :size :eccentricity
>make "n 0
>repeat 360
>[rt :n fd :size lt :n lt :n fd :size*:eccentricity rt :n make "n :n+1]
>end
>xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
>
>What am I doing wrong?
>
>Cheers Richard

=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v

                        Richard Impey
                        Assistant Principal (Acting)
                        Learning Technologies and Art Specialist
                        Phone 0011 61 3 9509 6872
                        Caulfield North Primary School
                        186 Balaclava Road
                        Caulfield North 3161
                        Melbourne, Victoria, Australia


=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v=v
=v


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