Drawing a parallel line

spireup

Hi

I want to be able to supply a line and a width to a method and have the method draw a rectangle based on that line and a parallel line that width apart.

I want to use this for drawing the footprints of walls that may be sloped or paths on sloped terrain etc.

My question is what is the precise transformation required to get this second parallel line? Im considering working either with points perhaps using the offset method or with vectors. Either way I need to figure out the right transformation.

One thing Im thinking is that a perpendicular line to the original line of length 'width' would be a useful vector. However when I try and calculate that I cant figure out which plane Im meant to rotate in to get it(is it multiple planes)!

One problem with perpendicular lines is i can see that there are at least two perpendicular lines to any one line ignoring direction.

thanks heaps for any help!

Paul

Dan Rathbun

You should be able to steal code from the box.rb example, since it creates a rectangle before it pushpulls it into a box.

TIG

If you are drawing these double lines on a 'surface' then picked-point at point1 can be used to return the best face below it - get the axis=face.normal...
If it's not on any face or you want it flat then axis=Z_AXIS
Then next picked_point point2 needs to be on that face, so get it's initial value and then use
point2=point2.project_to_plane(face.plane)
or if it's to be 'flat' use point2.z=point1.z instead so it's level with point1...
This gives you the first edge
edge12=entities.add_line(point1,point2)
To make it's offset 'clone'...
Assuming ' width' is the offset required.
point3=point1.offset(edge12.line[1],width)
rotate it into place...
tr=Geom::Transformation.rotation(point1,axis,90.degrees) point3.transform!(tr)
get the other end point
point4=point3.offset(edge12.line[1],edge12.length)
and then draw the offset edge
edge34=entities.add_line(point3,point4)