OneSpace Modeling: Controlling model clipping planes

This simple code example defines two functions which enable model clipping in the current viewport. The clipping plane position is derived from the current workplane. Thanks to Jörg Antweiler for the inspiration and the original code snippet in the German user forum.

(defun clipping-on ()
  (set_vp_model_clipping (oli:sd-inq-current-vp) :on)
  (set_vp_capping (oli:sd-inq-current-vp) :on)
  (set_vp_capping (oli:sd-inq-current-vp) :part-color)
  (model_clipplane :plane1 :off :plane1 :on
    :plane1_positioning :par_wp :ref_wp (oli::sd-inq-curr-wp) :done 
    :flip_plane :done)
)

(defun clipping-off ()
  (model_clipplane :plane1 :off)
  (set_vp_model_clipping (oli:sd-inq-current-vp) :off)
)

The interesting part of this example is not so much the end result, but how you get there, starting from a command sequence captured by the recorder tool. The original sequence looked rather like this:

set_vp_model_clipping "1"  :on set_vp_capping "1"  :on set_vp_capping "1"  
:part-color model_clipplane  :plane1  :off  :plane1  :on  :plane1_positioning  :par_wp 
:ref_wp "/s" :done :flip_plane :done
(PROGN
  (RESET-TOGGLE "MODIFY_CLIPPLANE_SA-VAR-GROUP-1-OPT-CONT-DONE-TB")
  NIL)
complete

As you can see, the recorder tool writes quite a bit of gobbledigook, and you need to massage it into a format which lends itself more easily to be used in real programs.

The first observation is that the RESET-TOGGLE command is only a UI by-product which can be simply omitted. The reasons why it's in the recorder file are quite internal, and in general you don't want to know .-) In any case, let's remove that from the sequence; I'll also throw in some formatting for free:

set_vp_model_clipping "1" :on 
set_vp_capping "1" :on 
set_vp_capping "1" :part-color 
model_clipplane :plane1 :off :plane1 :on 
                :plane1_positioning :par_wp :ref_wp "/s" :done 
                :flip_plane :done complete

Ahhh, that's much easier on the eyes now.

When looking at the above, any Lisp programmer who is worth his salt will start to shiver because of acute parentheses deprivation: "Where have all my beloved ( and ) characters gone?" In fact, the above doesn't even look like Lisp, rather like some... well... macro language, right?

Exactly. On top of OneSpace Modeling's Lisp subsystem runs a so-called action routine interpreter. This interpreter understands syntax such as the above. If you are familiar with the macro language in OneSpace Drafting, it will probably dawn on you quite quickly why the designers of OneSpace Modeling chose to implement such an interpreter - they wanted to provide similar macro entry capabilities for OSDM. (That funny complete token should definitely give it away...)

All the high-level commands in OneSpace Modeling, such as extrude, load_package, load_session and even exit are implemented in this manner, i.e. they can be entered without using any parentheses - and that is also the way those commands are captured by the recorder. Any functionality implemented via sd-defdialog can also be used in parentheses-free notation or, as we sometimes say, in action routine syntax.

High-level commands such as the above are also automatically endowed with certain services, such as recordability, UNDO handling, and automatic UI synchronization. But I'm mentioning this only to confuse you even more. The real reason why we're discussing this here is to show you how to convert recorder file syntax into something that can be used programmatically.

In fact, we're almost done. You need to know only a few things:

• High-level commands also work if you remove the trailing complete and enclose them in parentheses
• Arbitrary Lisp expressions can be used as an input for parameters of commands.

This leads us immediately to:

(defun clipping-on ()
  (set_vp_model_clipping (oli:sd-inq-current-vp) :on) 
  (set_vp_capping (oli:sd-inq-current-vp) :on) 
  (set_vp_capping (oli:sd-inq-current-vp) :part-color) 
  (model_clipplane :plane1 :off :plane1 :on 
                :plane1_positioning :par_wp :ref_wp "/s" :done 
                :flip_plane :done)
)

Which is almost the program presented at the beginning, except that we do not use oli:sd-inq-current-wp to inquire the current workplane, and that we do not have the code to disable clipping yet.

If you already read the Integration Kit documentation and especially the sections on sd-defdialog and sd-call-cmds, you will probably ask why set_vp_model_clipping and friends are not encapsulated in sd-call-cmds in the code above. Answer: They are, in this particular case, not part of any sd-defdialog code. Instead, the code is expected to be called directly from the user input line. In that case, you cannot use sd-call-cmds - but you must do this when calling/executing code such as the above in dialog context. That's a topic for another rainy day...

-- ClausBrod

---

To have it really comfortable we will have a third tiny function to realize a toggle behaviour and finally to create an "Available Command" to have a tool bar icon for quick access to our new function (in 2 different languages).

(in-package :sd-tools)
(use-package :oli)

;; insert the two known functions from above here..

(defvar *clipping-on-off* NIL)
(defun clipping-on-off ()
 (if *clipping-on-off*
   (progn
     (setq *clipping-on-off* NIL)
     (clipping-on)
     )
   (progn
     (setq *clipping-on-off* T)
     (clipping-off)
     )
   ) ;; end if
 ) ;; end defun

(sd-define-available-command
 "All" "Miscellaneous" "Clipping-On-Off"
 :groupTitle   (sd-multi-lang-string  "Miscellaneous" :german "Verschiedenes")
 :commandTitle (sd-multi-lang-string  "Clipping toggle" :german "Schneiden")
 :action       "(sd-tools::clipping-on-off)"
 :image        "SolidDesigner/View/clipping"
 )

Well, the icon (:image) is an already existing one. Create a new one if you like.

The complete example clipping_on_off.lsp can be loaded from the attachment area.

-- DerWolfgang - 25 Nov 2004

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