Routine to orient lines

[Neil Wilson]

I need to orient my linework so that the begin and end points of selected lines are all uniform (ie...delta x>0, delta y<0, etc.). I am not proficient in LISP or VB and would have to invest a considerable amount of time to develop the routine. I am sure someone has made a routine to do this. Would anyone be willing to share it or direct me to a site that has such a routine?

Also, is there any way to graphically show which direction the lines are drawn?

 

[Neil Wilson]

I should have investigated Quick Select before posting. I have a solution now.

Thank you.

 

[Neil Wilson]

It turns out that I do need help with this afterall. Using quickselect I can filter objects according to their Delta x or Delta y coordinates. I can then reverse the lines easily using the flip command in Land Desktop. However, this command does not work on arcs. Therefore, my request is for a routine to reverse the direction of an arc segment without changing it's geometry (ie...reverse the start x or start y coordinates).

Any guidance is appreciated.

 

[dean_bourke]

I don't know if that is possible.
An arc is defined by CENTRE, RADIUS, START ANGLE and END ANGLE (in radians). Therefore I don't think you can reverse an arc. Turning it into a polyine may be some help. BTW, why do you need to reverse it, maybe there is another solution?

Dean

 

[RDI]

Do a google search for "RPoly". It reverses the direction of a polyline.
Once you have that--do

(command ".pedit" arcent "y" "x") ;This'll convert it to polyline Run RPoly--not sure how to pass it the entity then explode the polyline back down to arc.

 

[Neil Wilson]

If you select an arc and view the list output, you will see that it has a start and end coordinate which define it's "direction". I need to control the direction for street address geocoding, which depends on the line direction to determine which side is left or right (even addresses on left, odd on right for example). If the start and end coordinates of an arc are reversed without changing the other parameters, then the arc would keep the correct geometry but the "direction" would be reversed. Thus the "left" and "right" sides would be flipped.

I see another post about converting the arcs to polylines and reversing them with a utility called RPOLY. I will be looking into this, but if there is a way to modify the arc without converting it to a polyline, I would prefer that solution.

I don't know if that is possible.
An arc is defined by CENTRE, RADIUS, START ANGLE and END ANGLE (in

radians). Therefore I don't think you can reverse an arc. Turning it into a polyine may be some help.

 

[Neil Wilson]

I found RPoly and it does reverse the arc if it is converted into a polyline. I can work with it as long as I leave the arc as a polyline. However, if I have to explode the polyline the arc reverts back to it's original orientation. This is a problem as I do occasionally have to explode my linework during editing. It would be cumbersome to have to go through my linework again to re-orient the arcs after exploding the polylines. I really need to modify the arc entity.

I was looking for a routine to reverse polylines, so your reply is very helpful.

Thank you

 

[Neil Wilson]

I was incorrect about seeing the end coordinates using "list". The end coordinates can be viewed in the properties viewer under geometry.

 

[Jeff Mishler]

Neil, an arc, as defined by Autocad, is ALWAYS drawn countrclockwise. Therefor, even though you can list the start & endpoints, they are not modifiable. The start and end angles can be modified, but it results in an arc that is (360deg - original_arc_delta). So I would say that you need to leave/make all linework as polylines.

Jeff

BTW, here is the arc description as written in the Developer's guide:
An arc is always drawn counterclockwise from the start point to the endpoint. The StartPoint and EndPoint properties of an arc are calculated through the StartAngle, EndAngle, and Radius properties.

 

[dean_bourke]

I am using ACAD2004, and when I LIST an arc I get this:

ARC Layer: "0"
Space: Model space
Handle = 9B
center point, X= 49.9744 Y= -32.7696 Z= 0.0000
radius 59.7602
start angle 117
end angle 147
length 30.5231

The PROPERTIES box does show a start and and end point but I believe the direction of the arc is determined by center,radius,start angle and end angle - always in the direction specified in the UNITS command. You may have some luck converting the arc to a polyine. Some short tests I have run indicate that the vertices do indeed reverse when mirrored for example, but when exploded the arc always returns to it's original data.

Dean