Drawing A Polyline with AutoLISP 4

Now I'm going to talk about all the functions of the AutoLISP program. I already gave you a list of all the functions. Here it is again:


The Functions


Function Action


START Setting the limits, erasing everything in the screen, setting the snap and grid, zooming out of the screen


DRLNS Drawing four lines


FNDET Finding line or polyline entity


DELPL Delete polyline


DRWPL Draw polyline, no intersection with other line


DPLIP Draw polyline, intersection with other line


ENDPR Ending of the program


The START And The END Function


Earlier I talked about those two functions. You know how they work. I don't have to tell you once more.


The DRLNS Function


This function is used to draw the lines in the screen. It is a very simple function. The LINE command is used twice.


Here is the function.


(defun-drlns-()
---(command-"line"-(list-120-0)
-------------------(list-10-0)
-------------------(list-10-120)
-------------------(list-120-120)
-------------------""
---)
---(command-"line"-(list-10-60)
-------------------(list-120-60)
-------------------""
---)
)


The FNDET Function


Let's first talk about this function. Let me tell you what it does. Let me tell you what is happening through the function.


There is asked to make a selection. A selection could have bene made or there is no selection made. The right mouse button is clicked.


What ever is done. A selection has been made or no selection has been made. An entity and the selection point is given back.


If a selection has been made, then a polyline has been selected or a line. If a polyline has been selected, then the points of it are found.


After the points have been found, the polyline is deleted and the line under the polyline is found. The points are needed for doing that.


If a line has been selected, then the entity of the line can easily be found. And the selection point is known too.


If no selection has been made, then the entity and the selection point, that are given back to the main program, get the value of nil.


Here is the FNDET function.


(defun-fndet-(/-an-el-et-ls-p1-p2-pt-sl-sp-ss-tp)
---(setq-sl-(entsel-"\nSelect-line: "))
---(if-sl
------(progn
---------(setq-et-(car-sl)
---------------el-(entget-et)
---------------sp-(cadr-sl)
---------------sp-(osnap-sp-"nea")
---------------tp-(cdr-(assoc-0-el))
---------)
---------(setq-ls-nil)
---------(if-(=-tp-"LWPOLYLINE")
------------(progn
---------------(while-(setq-nr-(caar-el))
------------------(if-(=-nr-10)
---------------------(progn
------------------------(setq-pt-(cdar-el))
------------------------(if-ls
---------------------------(setq-ls-(append-
-------------------------------------(list-pt)
-------------------------------------ls
------------------------------------)
---------------------------)
---------------------------(setq-ls-(list-pt))
------------------------)
---------------------)
------------------)
------------------(setq-el-(cddr-el))
---------------)
---------------(setq-p1-(nth-1-ls)
---------------------p2-(nth-0-ls)
---------------------an-(angle-p1-p2)
---------------)
---------------(command-"erase"-et-"")
---------------(setq-ss-(ssget-"c"-(polar-p1-
------------------------------------------an-
------------------------------------------1
-----------------------------------)
-----------------------------------(polar-p2-
------------------------------------------(+-an
---------------------------------------------pi
------------------------------------------)
------------------------------------------1
-----------------------------------)
------------------------)
---------------)
---------------(setq-et-(ssname-ss-0))
------------)
---------)
------)
------(setq-et-nil
------------sp-nil
------)
---)
---(list-et-sp)
)


I have told you what the function does. And I have told you what is happening through the function. Lets now see how it done.


Asking to make a selection. It is done with this line. The ENTSEL function is used. That function gives back a list.


(setq sl (entsel "\nSelect-line: "))


This is an example of the list that is given back by the ENTSEL function.


(<Entity name: 37d85a0> (61.8922 59.7297 0.000000))


If a selection has been made, then we want to know the name of the entity and the selection popint. We use these lines.


(setq-et-(car-sl)
el-(entget-et)
sp-(cadr-sl)
sp-(osnap-sp-"nea")
tp-(cdr-(assoc-0-el))
)


First we find the name of the entity. It is the first element in the list from the ENTSEL function. We use the CAR function.


The second element of the list is the selection point. To find it we use the CADR function. And we use the OSNAP function.


The OSNAP function is used to have the point laying on the polyline or the line that has been selected.


We also want to know the type of the entity. The type can be LINE or LWPOLYLINE. A polyline has been selected if it is LWPOLYLINE.


We find the type of the entity with this line.


(setq-tp-(cdr-(assoc-0-el))


If a line has been selected, then we have the name of the entity and the selection point. But a polyline could have been selected.


If a polyline has been selected, we need to find the points of the polyline. This is how it is done:


(while (setq nr (caar el))
(if (= nr 10)
(progn
(setq pt (cdar el))
(if ls
(setq ls (append (list pt) ls))
(setq ls (list pt))
)
)
)
(setq el (cddr el))
)


I start with a WHILE loop. The WHILE loop continues as long as a number has been found. The number is in the sub list of the entity list.


The CAAR function is used. With that function the first sub list of the entity list is taken and the first element in it.


There is checked if that number is ten. If so, the point is found in the sub list with the CDAR function.


Next the first sub list of the entity list is removed from the entity list with the CDDR function. And we continue with the WHILE loop.


The points of the polyline are found in the sub lists that have the number ten. We create a list. The kist has two points.


After the points have been found, the polyline is deleted and the line under the polyline is found. The points are needed for doing that.


The polyline is deleted with this line:


(command-"erase"-et-"")


These are the lines that are used to find the line under the polyline. We use the points of the polkyline for doing that.


Here are the programming lines:


(setq-ss-(ssget-"c"-(polar-p1-an-1)
(polar-p2-(+-an-pi)-1)
)
)
(setq-et-(ssname-ss-0))


The angle between the point P1 and P2 is measured. And the points of the SSGET function are one from the points.


We do not want to find the lines that cross the line at the points P1 and P2. That is why we go to points 1 from the original points.


We find a selection set. I call it SS. The first entity in the selection set is the line that we are looking for. Here is the programming line.


(setq-et-(ssname-ss-0))


If a line has been selected, then the entity of the line can easily be found. And the selection point is known too.


If no selection has been made, then the entity and the selection point, that are given back to the main program, get the value of nil.


Very good. We have found the line and we have found the selection point. Those two are put in a list and given back to the main program.


We put these two in a list. This is how it is done:


(list-et-sp)


Next Post


I have talked about the FNDET function. You have got a lot of information. I hope I was clear enough. If not, let me know.


In my next post I'm going to talk about the DELPL function. That function is used to delete the polyline that has been drawn.


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