Bug or what unable to draw line tangent from circle if circle has point on it


Please try this.
Draw a 3mm dia circle using ‘circle diameter’ tool then draw a line from it using line tangent from curve tool. it works

now place a point a few mm below that circle, and repeat the exercise creating the circle starting at that point. and ending off to the right (horiz) this is where I drew mine.

I am unable to get any line using line tangent from curve to appear heading away from that circle.

Delete the point, makes no difference,


Seems to work OK here- are all snaps off after you place the first point on the second circle??


The white line is a tool so you can bias the pick towards where the tangent line will originate. Think about it. There are two possibilities for a line tangent to a circle that passes through a point. Rhino can’t guess which one you want so you bias that choice by where you pick using the while line visual tool.

understand purpose of line, I am clicking on the upper half of the circle at about 11oclock, it simply wont form a line
I can draw a circle without starting it at a point, and all works.

I have just near active as osnap, ortho off, project off, everything I can think of is off, just tried it with no osnaps, still fails.
attached the actual circle that sparked off this mystery, I have drawn another one above it and that works.

I also drew a series using same tool and R6,0

then r5,0 etc down to r3,0 and all worked ok.

I go back to the one that matters and it refuses to allow a line to form.

attached the item copied out to a new rhino file, still it fails.

I simply wanted to draw a tangent line from upper part of circle to the point north east of it.

I actually am aiming to use interCrv to place a curve, starting tangent vertical from the first point at far right, then through the two points upper points ending tangent onto the 3mm circle top. as there is no end tangent onto curve option, I have to somehow establish where the best end point will be, hence use of the line tangent tool.

Any suggestions on finding the exact spot on the circle to end my curve so that it sweeps into the circle arc also welcome ! after trimming it should be a smooth aerofoil not likely to cause ripples when skinning.
line tangent from circle issue.3dm (28.3 KB)

another experiment…I draw a triangle from the point the circle starts from to the top right point then to the point below that and back to the circle.
move that triangle off to the left. create a new 3mm dia circle, from centre, move that using quad to snap it to triangle, use line tangent to circle on that circle and it refuses to see a line develop. draw another circle 3mm dia nearby, and that works.

Its as if anything associated with that circle corrupts a circle attached to it.

However I was able to place a new point somewhere nearby, and draw a circle starting from it using circle diameter tool, and it wouldnt then allow the tangent line from circle tool to work.

draw a circle without having to do it through a point, and all is well

another test. the offending circle, draw a line 10mm long from its centre, draw acircle centred on the line end, that circle now refuses to see a line tangent drawn from it.


It’s possible the endpoint of the circular curve is near there and getting in the way.
Try using the CrvEnd tool to mark the end. If it’s close by, then use CrvSeam to move it to a less important location.

Not aware of CrvEnd and a circle having an end, I learn something every day, however run that command and I see a black square at 6 oclock, so its no where near my pick point.

3dm attached in my last post.


Yeah… I see… The new (little) circle is not in the same plane as the original, it will be more as you expect if the Planar setting in the status bar is active. I’m not sure what should happen here, I’ll poke at it some more.