Topic: How to Entmake these 2 LWPOLYLINE?

[HasanCAD]

I remeber that I had read that befoe but can not find.

Please help

[MP]

I remeber that I had read that befoe but can not find.

Do you have a cold? Mojo sent.

[JohnK]

*rofl*

[ScottBolton]

Both lines from 0,10 > 0,0 > 10,0, the second with a 5.0 fillet - note the "bulge" on the second vertex (for some reason it's displayed here as a phone number - dunno how to stop it!).

(entmake '((0 . "LWPOLYLINE") (100 . "AcDbEntity") (67 . 0) (410 . "Model") (8 . "0") (100 . "AcDbPolyline")
      (90 . 3) (70 . 0) (43 . 0.0) (38 . 0.0) (39 . 0.0)
      (10 0.0 10.0) (40 . 0.0) (41 . 0.0) (42 . 0.0)
      (10 0.0 0.0) (40 . 0.0) (41 . 0.0) (42 . 0.0)
      (10 10.0 0.0) (40 . 0.0) (41 . 0.0) (42 . 0.0)
      (210 0.0 0.0 1.0)
      )
    )
(entmake '((0 . "LWPOLYLINE") (100 . "AcDbEntity") (67 . 0) (410 . "Model") (8 . "0") (100 . "AcDbPolyline")
      (90 . 4) (70 . 0) (43 . 0.0) (38 . 0.0) (39 . 0.0)
      (10 0.0 10.0) (40 . 0.0) (41 . 0.0) (42 . 0.0)
      (10 0.0 5.0) (40 . 0.0) (41 . 0.0) (42 . 0.414214); < this isn't a Skype number! ;
      (10 5.0 0.0) (40 . 0.0) (41 . 0.0) (42 . 0.0)
      (10 10.0 0.0) (40 . 0.0) (41 . 0.0) (42 . 0.0)
      (210 0.0 0.0 1.0)
      )
    )

If you are unsure how the (entmake should be made up, first create the element then issue (entget (car (entsel))) on it and look at the structure. (Similar for STYLES, etc.)

S

[Daniel J. Ellis]

The "strange" number of the bulge amount (DXF 42) clearly refers to the angle, somehow.

0.414214 is ten times the square root of two.  The cosine and sine of 45 degree is the inverse of root 2.

Forgotten too much of my A-Level Maths to turn that into anything useful, but that's wher ethe funny number comes from!

dJE

[HasanCAD]

The "strange" number of the bulge amount (DXF 42) clearly refers to the angle, somehow.

0.414214 is ten times the square root of two.  The cosine and sine of 45 degree is the inverse of root 2.

Forgotten too much of my A-Level Maths to turn that into anything useful, but that's wher ethe funny number comes from!

dJE

That means this number is fixed, Isn't it?

[Daniel Eiszele]

The bulge value is explained in many resources.  Here is one of them http://www.afralisp.net/archive/lisp/Bulges1.htm

[Lee Mac]

0.414214 is ten times the square root of two.

Not where I come from it isn't...

The Bulge is the tangent of a quarter of the included angle, positive for a bulge in the anticlockwise direction, negative otherwise.

Hence for a bulge as shown in your diagram:

Code: [Select]

Angle = pi/2
Direction = Anticlockwise

Bulge = tan (pi/8) = 0.41421 = (sqrt(2) - 1)

Or in code:

Code: [Select]

;; <angle>  -  +ve for anticlockwise, else negative.
(defun _GetBulge ( <angle> )  
  ((lambda ( a ) (if (equal 0.0 (cos a) 1e-14) nil (/ (sin a) (cos a)))) (/ <angle> 4.0))
)

[JohnK]

0.414214 is ten times the square root of two.

Not where I come from it isn't...
...

*lol*
I would have also accepted: "Nope." or *blink-blink* or even *bleh*.

EDIT: Late entry:
"Did you find that information in the alt.swedish.chef.bork.bork.bork newsgroup" (or something similar).



Its just too bad that sarcasm is so difficult to convey properly without inflection.