How to draw a line prependecular to present line?

[khoshravan]

This situation occurs to me a lot and every time I have difficulty drawing it.

 

I have a general line (inclined, but don't know angle).

From a specific point on this line I want to draw a prependecular line to first line.

 

I draw this way:

 

I draw a prependecular line from a point outside the inclined line and then I move it to the specific point on the inclined line.

 

I think there must be an easier way to perform this task but I don't know how.

Any comment is wellcome.

 

[SEANT]

How about this command macro:

 

^C^C_xline;_a;_r;\90;

 

It creates a construction line perp to a selected line or polyline segment.

[lpseifert]

Turn on Ortho

UCS > OBject > pick your 'general line'

draw new line

UCS > Previous to return the last UCS

[alanjt]

Use polar 'relative to last object'.

[khoshravan]

Thanks a lot. It was a very smart solution

 

Turn on Ortho

UCS > OBject > pick your 'general line'

draw new line

UCS > Previous to return the last UCS

[khoshravan]

Could you please explain a little bit more.

I got your idea but I don't know how to do the "relative to last object" part.

 

Use polar 'relative to last object'.

[alanjt]

Could you please explain a little bit more.

I got your idea but I don't know how to do the "relative to last object" part.

Sorry about that...

[khoshravan]

Sorry for a newbie level question.

I am not familiar with command macro in AutoCAD.

Please tell me where should I put this command?

 

How about this command macro:

 

^C^C_xline;_a;_r;\90;

It creates a construction line perp to a selected line or polyline segment.

[khoshravan]

In this solution I think the inclined line (the general line) should be drawn just before drawing the perpendicular line.

Otherwise "relative to last segment" advantage could not be used.

Am I right? If so it diminishes the generality of the solution. But anyway thanks for your solution.

 

Sorry about that...

[ATTACH]21438[/ATTACH]

[khoshravan]

Dear All

 

Thanks to all of you for your generosity to give your ideas which solved my task in different ways. Personally I like lpseifert's idea and will use it.

 

Also I was expecting an answer with "temporary track point" in object snap usage but it didn't. Very interesting that I was too far from best solutions.

[alanjt]

In this solution I think the inclined line (the general line) should be drawn just before drawing the perpendicular line.

Otherwise "relative to last segment" advantage could not be used.

Am I right? If so it diminishes the generality of the solution. But anyway thanks for your solution.

Last segment is last segment snapped to. Do a nearest/end, etc. snap from any line/pline, etc. and see.

[SEANT]

Sorry for a newbie level question.

I am not familiar with command macro in AutoCAD.

Please tell me where should I put this command?

 

It is not a task I would recommend for a beginner necessarily, but a command macro can be assigned to the AutoCAD user interface via the CUI command. See these links for some information:

 

http://www.cadtutor.net/corner/2006/january.php

 

http://www.cadalyst.com/cad/autocad/create-your-own-autocad-commands-circles-and-lines-autocad-tutorial-6308

 

Essentially, the macro automates this sequence of commandline inputs:

 

Command: _xline Specify a point or [Hor/Ver/Ang/Bisect/Offset]: a

Enter angle of xline (0) or [Reference]:  r

Select a line object:
Enter angle of xline <0>: 90

Specify through point:

 

The sad fact of the matter is that all three suggestions in this thread have their strengths and weaknesses.

 

Xlines will likely require trimming.

 

UCS-Entity may not always set a useful coordinate system. See Line in attached

 

‘Relative to last object' may not be available from all positions on a linear segment (i.e., Intersections, Polyline vertex, etc). See Poly in attached.

 

This area warrants additional attention from AutoCAD programmers, at Autodesk or otherwise. As idle as the above comment may seem, it is not unfathomable - given the participants of this thread.

PerpTest.dwg

[khoshravan]

 

UCS-Entity may not always set a useful coordinate system. See Line in attached

 

This is a good example and thanks for showing the short comes. But still I can use ucs method to draw a perpendicular line in your attached file (see attached file).

 

Obviously the vertex on the right side causes the ucs to behave oddly. Also the ucs symbol appears strangely. Will be happy to hear the reason, if you have time to explain.

PerpTest.dwg

[SEANT]

This is a good example and thanks for showing the short comes. But still I can use ucs method to draw a perpendicular line in your attached file (see attached file).

 

Obviously the vertex on the right side causes the ucs to behave oddly. Also the ucs symbol appears strangely. Will be happy to hear the reason, if you have time to explain.

 

Set the UCS back to World, then check the Z values of the Start- and EndPoints of that new line:

 

                  LINE      Layer: "0"
                           Space: Model space
                  Handle = 209
             from point, X=   1.9404  Y=   5.4967  Z=   2.4967
               to point, X=   4.3341  Y=  -2.4822  Z=  -5.4822
Extrusion direction relative to UCS:
                  X=   0.0000  Y=  -0.7071  Z=   0.7071
         In Current UCS, Length =   8.3302,  Angle in XY Plane =    287
                 3D Length  =  11.5349,  Angle from XY Plane =    316
                 Delta X =   2.3937, Delta Y =   -7.9789, Delta Z =  -7.9789

 

While the initial line was coplanar to the world XY:

 

                  LINE      Layer: "0"
                           Space: Model space
                  Handle = 1ea
             from point, X=   0.0000  Y=   0.0000  Z=   0.0000
               to point, X=  10.0000  Y=   3.0000  Z=   0.0000
Extrusion direction relative to UCS:
                  X=   0.0000  Y=  -0.7071  Z=   0.7071
         Length =  10.4403,  Angle in XY Plane =     17
                 Delta X =  10.0000, Delta Y =    3.0000, Delta Z =   0.0000

 

The UCS-Entity command reads info from that initial line that is not readily apparent (see Extrusion direction relative to UCS).