Draw an isosceles trapezoid

[andy_lee]

Hi guys

Have a routine like this? Thanks for any help!

Enter the value of the " L " and " H" , pick a basic point , Dynamic specified direction. Draw an isosceles trapezoid.

 

Dynamic specified direction

[BIGAL]

A good start for learning lisp very easy just a couple of commands think of it as 5 pts 1st point is pick point then using new pt = polar angle distance or old fashioned trig can work out all the corners then create pline pt1 pt2 pt3 pt4 C and then rotate.

[Tharwat]

Try this Andy and let me know

 

(defun c:Test (/ dtr ac ab p sl a b c d e p)
 ;;	Author : Tharwat Al Shoufi			;;
 ;; Draw Trapezoid with angle 55 on the two sides	;;
 ;; --------------------------------------------------	;;
 (defun dtr (a) (* pi (/ a 180.0)))
 (if (not *traplen*)
   (setq *traplen* 10.0)
 )
 (if (not *traphgt*)
   (setq *traphgt* 4.0)
 )
 (if (and (setq *traplen* (cond ((getdist (strcat "\n Specify Length of Trapezoid < " (rtos *traplen* 2 2) " > :")))
                                (*traplen*)
                          )
          )
          (setq *traphgt* (cond ((getdist (strcat "\n Specify Height of Trapezoid < " (rtos *traphgt* 2 2) " > :")))
                                (*traphgt*)
                          )
          )
          (setq ac (/ *traphgt* (sin (dtr 55.)))
                ab (* ac (cos (dtr 55.)))
          )
          (if (>= (setq sl (- *traplen* (+ ab ab))) 0.)
            (setq p (getpoint "\n Specify top center point of Trapezoid :"))
            (progn (alert "Length of Trapezoid is too small !!") nil)
          )
     )
   (progn (setq a (polar p pi (/ sl 2.))
                b (polar a (dtr 235.) ac)
                c (polar b 0. *traplen*)
                d (polar c (dtr 125.) ac)
                e (entmakex
                    (append (list '(0 . "LWPOLYLINE") '(100 . "AcDbEntity") '(100 . "AcDbPolyline") '(90 . 4) '(70 . 1))
                            (mapcar '(lambda (pt) (cons 10 (list (car pt) (cadr pt)))) (list a b c d))
                    )
                  )
          )
   )
 )
 (if e
   (command "_.rotate" e "" "_non" p "\\")
 )
 (princ)
)

[andy_lee]

Try this Andy and let me know

 

Many Thanks , Tharwat. It's nice! Is just what I need !

[Tharwat]

Many Thanks , Tharwat. It's nice! Is just what I need !

 

Happy to hear that and you are welcome .

[NhonG]

Hi Tharwat,

 

 

Kindly asking to another solution to draw difference four sides (input) and angle of trapezoid (angle not fix). How to add more feature in your code? Thank you in advance.

 

 

[Lee Mac]

See this thread: http://www.theswamp.org/index.php?topic=39256

[BIGAL]

As Lee is stating without a known angle there is no solution. How do you do this now you must be fixing something or do you have a diagonal distance then its solvable.

[eldon]

Having an idle moment, I tried to draw the shape as dimensioned. Not straight forward

[BIGAL]

Eldon I got Length = 263.495 not 265 so diagram is not correct for whole degrees

[eldon]

Eldon I got Length = 263.495 not 265 so diagram is not correct for whole degrees

 

When I saw the picture, I thought that it showed typical OOB settings, with the length precision set at 4 and the angle precision set at 0, with decimal degrees set in the dimensions.

 

So that meant that there was up to half a degree tolerance in each angle, which when dimensioned would be as shown.

 

I got 1.8 units misclosure going round with whole angles. So I adjusted angles here and there, keeping the adjustments below half a degree.

 

For the record, here are the angles that I used:-

70°-33'-34" (dimensioned as 71°)

74°-45'-54" (dimensioned as 75°)

91°-29'-55" (dimensioned as 91°)

123°-10'-37" (dimensioned as 123°)

 

These values are probably not unique, but once I had found one set, I was content.

[Lee Mac]

Regarding uniqueness: if all four lengths are constrained, only one angle is required for uniqueness; if all four lengths are given & more than one angle is specified, the geometry will be over-constrained unless the given angles are exact. I find the best way to visualise this is to reduce the problem to a rectangle which may be deformed into an infinite set of parallelograms unless an angle is given.

[AIberto]

Try this Andy and let me know

 

(defun c:Test (/ dtr ac ab p sl a b c d e p)
 ;;	Author : Tharwat Al Shoufi			;;
 ;; Draw Trapezoid with angle 55 on the two sides	;;
 ;; --------------------------------------------------	;;
 (defun dtr (a) (* pi (/ a 180.0)))
 (if (not *traplen*)
   (setq *traplen* 10.0)
 )
 (if (not *traphgt*)
   (setq *traphgt* 4.0)
 )
 (if (and (setq *traplen* (cond ((getdist (strcat "\n Specify Length of Trapezoid < " (rtos *traplen* 2 2) " > :")))
                                (*traplen*)
                          )
          )
          (setq *traphgt* (cond ((getdist (strcat "\n Specify Height of Trapezoid < " (rtos *traphgt* 2 2) " > :")))
                                (*traphgt*)
                          )
          )
          (setq ac (/ *traphgt* (sin (dtr 55.)))
                ab (* ac (cos (dtr 55.)))
          )
          (if (>= (setq sl (- *traplen* (+ ab ab))) 0.)
            (setq p (getpoint "\n Specify top center point of Trapezoid :"))
            (progn (alert "Length of Trapezoid is too small !!") nil)
          )
     )
   (progn (setq a (polar p pi (/ sl 2.))
                b (polar a (dtr 235.) ac)
                c (polar b 0. *traplen*)
                d (polar c (dtr 125.) ac)
                e (entmakex
                    (append (list '(0 . "LWPOLYLINE") '(100 . "AcDbEntity") '(100 . "AcDbPolyline") '(90 . 4) '(70 . 1))
                            (mapcar '(lambda (pt) (cons 10 (list (car pt) (cadr pt)))) (list a b c d))
                    )
                  )
          )
   )
 )
 (if e
   (command "_.rotate" e "" "_non" p "\\")
 )
 (princ)
)

 

 

Dear Tharwat

 

Why can't use for 3D mode , , like this .

 

[andy_lee]

Dear Tharwat

 

Why can't use for 3D mode , , like this .

 

[ATTACH=CONFIG]54752[/ATTACH]

 

Yes , This is a disadvantage.

 

Hi Tharwat. can fix this ?

[BIGAL]

Tharwat tried using new ucs in plane but did not work, a more polar method 4 points would, but anyway I cheated and used rotate3d to get the answer. Something in the entmakex.

 

Edited July 21, 2015 by BIGAL

[andy_lee]

Tharwat tried using new ucs in plane but did not work, a more polar method 4 points would, but anyway I cheated and used rotate3d to get the answer. Something in the entmakex.

 

[ATTACH=CONFIG]54913[/ATTACH]

 

Hi BIGAL ,Can you fix this?

[NhonG]

See this thread: http://www.theswamp.org/index.php?topic=39256

 

Thank you for your information.

[andy_lee]

Tharwat tried using new ucs in plane but did not work, a more polar method 4 points would, but anyway I cheated and used rotate3d to get the answer. Something in the entmakex.

 

[ATTACH=CONFIG]54913[/ATTACH]

 

feasible? BIGAL

[AIberto]

Hi andy

Maybe Marko can help .

 

You can look here

http://www.theswamp.org/index.php?topic=49677.msg548509#msg548509

[andy_lee]

Hi andy

Maybe Marko can help .

 

You can look here

http://www.theswamp.org/index.php?topic=49677.msg548509#msg548509

 

Thank you AIberto, Marko is great. Just wait.