Line perp from curve...cannot fathom out this tool!

Rhino Rhino for Windows
1

Hi,
This is driving me mad.

I want to be able to draw a perp line out from a picked location on a curve.

I wish to draw a line from a curve, going out from a location I pick on that line, its a location where another line intersects that curve in my current need, though it might be a point I choose maybe middle of a curve.

I have tried o for point on curve, also P for point. the line just wanders about with no perpness at all !!!

i see if one just uses it without choosing anything, then an option appears From first point for the end of the line.

and CommandHelp says it draws a perp line from first point.

Aha…there is hope…

But how to tell it about first point,

start again and select Line perp from curve, pick the point I want the line perp from, but then that From first point option isnt there for the next click !!! Its only there if you dont pick a first point !

Steve

2

The initial pick is really a pick to tell Rhino what curve to be perp to - after than it tracks around and you can click again to actually set the first point. The initial pick point is marked with a blip and if you use FromFirstPoint rather than clicking on a point on the curve then that is the point from which the perp line will be drawn.

-Pascal

3

Hi,
attached the actual task, I wish a perp line out heading north east from arrow tip place on curve.

I get the feeling the words in the prompt are misleading.

Looking at what you say Pascal…

<<The initial pick is really a pick to tell Rhino what curve to be perp to

  • after than it tracks around and you can click again to actually set
    the first point.>>

so there are three picks allowed, first selects the line, second selects the start point and third the end point.

It is however only allowing me two picks…

lets try again…
so select the tool, see a white line moving up and down red line as osnap ( near and int) finds the line.

It is asking Start of Line…in my brain that means where I want the line to go out from, as it would to anyone.

lets go with that…(should it in fact say pick the line or pick start line as opposed to Start of Line ? )

…I pick the start point… (where arrow tip is)…in attached actual task.
it now says End of Line (Point FromFirstPoint)

<< if you use FromFirstPoint rather than clicking on a point on the curve
then that is the point from which the perp line will be drawn.>>

so I hit F and enter and pick that point again and there is no further option to take. game over.

Lets try again…
this time first pick will be just the line somewhere near the arrow tip.

second pick its asking End of Line (point FromFirstPoint) now to anyone, this is going to be confusing, I hit F and enter and its making a line going up and down my red line.

try again , first pick near arrow tip on red line, I then hit F and enter at End of Line prompt which is the next prompt that appears and mouse move sees a line following my red line. the cross hairs dont have a snap when it gets to arrow tip. and I do have snaps on.

I also try with project on and off…in fact I am confused …is project on or off when button depressed ?
disable is on when depressed, yet project is off when depressed…am I right ? appears that way…very confusing, rather it had a tick box !!!

I try it both ways, makes no difference, just a thought incase project was on and messing things up.

1 hr trying to draw one line…
Line perp from curve problem.3dm (30.2 KB)
Steve

4

This is another case where simplifying the curve (SimplifyCrv) allows it to work. How are you making the curves that are inputs? We need to fix something in whatever that process is, probably, as well as the perp and tan finders in the commands you are using.

Hmm - I take it back- reopening your file and it seems to work as expected…

-Pascal

5

Yes, that is confusing. Line, perpendicular from curve is letting me draw a line in any direction I d*mn well want, which isn’t very productive.

As a workaround, use Circle, AroundCurve option. This will let you snap a circle centre to the end of the arrowhead and pull out an arbitrary radius. If you then draw a Line from the arrowhead to any point on the circle, it will be perpendicular to the original line.

Edit: the Line command is being perverted by the arrow head. If I place a point at the tip, then delete the arrow, the command behaves as I would expect. Looks a bit buggy to me.

6

Hi,
Pascal, see my other post on the tan tan rad failure, its that top curve, came from that nice looking pure networkSrf I did, link to that is in the tan tan rad post. (paper chase !)
The curves used in the network surf were InterpCrv drawn through lets say 10 or so planar points, aerofoil section data. so they started life as a curve with minimal points. NetworkSrf them and you see the result in the tan tan rad post (3dm was attached.
slice through them with an extruded surface, edge of slice is our curve , many points, so I FitCrv it to lessen such.

I must retain exactly its shape. Rebuild loses its shape.

simplify curve …? would that retain its exact shape ? i seem to recall trying both rebuild and also simplify, concluding they altered it, then found FitCrv.

MattE

I select the tool Circle AroundCurve

in top view I click on arow tip, and I cant get a circle, I get something that goes masive and thin.

Even if it did draw a circle, you say draw a line then from circle centre to circle edge, that line will be perp, but what am I looking to snap to, quad, ? else it will be like a sweeping clock hand and do any angle ?

Steve

Steve

7

Try doing it in the perspective viewport :smile:

8

Well, even if Line Perpendicular is working properly, the same problem will apply with that command too. Asking for a line to be perpendicular to another isn’t enough to define a specific vector. As you say, you can choose any direction in a 360 degree sweep around the original pick point. The circle has in effect constrained you to a plane.

So you need to supply (i.e. construct) a further constraint to define the vector that you’re after. At least with the Circle Perpendicular in place, you’ve got something to intersect this ‘second constraint’ with. Next up, how can you you define it (the second constraint)?

9

Hi, I presumed that drawing the line perp from curve with that tool in an ortho view would planar the line in that view, for me i needed it sitting on XY plane so used top view.

Surely this tool shouldnt be this involved.

I have used it in V4 for yrs , never had this nightmare.

If I have many lines perp to draw, drawing circles, then creating secondary constarints…

this tool needs a makeover, something is wrong. wording of steps, Pascals three clicks yet it gives me only two.

Steve

10

I’ve just tried to draw the perpendicular line (headed North East in Top view) from the curve and it works fine, as long as you place a point at the tip of the leader and then delete the leader first. That’s why I say it looks a bit buggy in this respect. Ortho is on, Planar is on.