Viewport points

Hey all,

I want to lisp something that checks whether a given point is within the

current viewport or not.

Anybody has any idea ?

Thanks.

Consider the following functions:

[color=GREEN];; On Screen-p  -  Lee Mac[/color]
[color=GREEN];; Returns T if the given point is visible in the active viewport.[/color]

([color=BLUE]defun[/color] LM:OnScreen-p ( p [color=BLUE]/[/color] c h v )
   ([color=BLUE]setq[/color] c ([color=BLUE]trans[/color] ([color=BLUE]getvar[/color] 'viewctr) 1 0)
         h ([color=BLUE]/[/color] ([color=BLUE]getvar[/color] 'viewsize) 2.0)
         v ([color=BLUE]list[/color] ([color=BLUE]*[/color] h ([color=BLUE]apply[/color] '[color=BLUE]/[/color] ([color=BLUE]getvar[/color] 'screensize))) h)
   )
   ([color=BLUE]apply[/color] '[color=BLUE]and[/color] ([color=BLUE]mapcar[/color] '[color=BLUE]<[/color] ([color=BLUE]mapcar[/color] '[color=BLUE]-[/color] c v) p ([color=BLUE]mapcar[/color] '[color=BLUE]+[/color] c v)))
)

[color=GREEN];; Viewport Extents  -  Lee Mac[/color]
[color=GREEN];; Returns two WCS points describing the lower-left and[/color]
[color=GREEN];; upper-right corners of the active viewport.[/color]

([color=BLUE]defun[/color] LM:ViewportExtents ( [color=BLUE]/[/color] c h v )
   ([color=BLUE]setq[/color] c ([color=BLUE]trans[/color] ([color=BLUE]getvar[/color] 'viewctr) 1 0)
         h ([color=BLUE]/[/color] ([color=BLUE]getvar[/color] 'viewsize) 2.0)
         v ([color=BLUE]list[/color] ([color=BLUE]*[/color] h ([color=BLUE]apply[/color] '[color=BLUE]/[/color] ([color=BLUE]getvar[/color] 'screensize))) h)
   )
   ([color=BLUE]list[/color] ([color=BLUE]mapcar[/color] '[color=BLUE]-[/color] c v) ([color=BLUE]mapcar[/color] '[color=BLUE]+[/color] c v))
)

(defun c:test ( / c r h w ul lr)
   (setq c (getvar 'viewctr))
   (setq r (getvar 'screensize))
   (setq h (/ (getvar 'viewsize) 2))
   (setq w (* h (/ (car r) (cadr r)) )
         ul (list (- (car c) w) (+ (cadr c) h))
         lr (list (+ (car c) w) (- (cadr c) h))
   )
 (princ)
)

Lee, I have used the above in conjunction with (ssget "_c" ul lr), but am curious why you used the trans function (UCS to WCS)? Is this just a form of error trapping?

but am curious why you used the trans function (UCS to WCS)?

Because the VIEWCTR system variable is expressed relative to the active UCS and I wanted the points returned by the function to be expressed relative to WCS.

I did not know that. Thank you, Lee.

No worries!