Newbie question: extrude following a straight line in space

mykape

Hello,
sorry, I've got a probably quite stupid newbie question:

I am trying to extrude an aluminium profile along a line
in space.
So e.g. my "line in space" goes from 0,0,0 to 5,5,5.
The "profile" shall be a rectangle of 0.1, 0.1, 0.2
The "profile" shall hang on the underside of my line
(exactly in the middle).

How can I tell Ruby to draw this rectangle perpendicular
to the "line in space", so I can extrude it afterwards?
The upper edge of the "profile" would be level with
the plane of the x and z axis and perpendicular to the
"line in space"

It's probably be done with the cross product of my
"line in space" and a second vector. But how to to
calculated the projection of the "line in space" on
the plane (so that I can find out the angle relativ
to the world axis).

Or is there an easier way by creating a new coordination
system with the "line in space" as one of the axises?

Sorry for my English (which is excellent compared to my Ruby .
By the way, thanks to everybody who invested in the various tutorials
and postings here - it did help me a lot to get that far!

Best regards
Klaus

Jim

I do not know your purpose of the plugin, but it seems like you would want to create a ComponentDefinition from the extruded profile so the Component could be re-used without re-drawing it each time.

Typically, you would draw the extrusion in the definition along an axis, then place the component and rotate it to the desired position.

mykape

Hello Jim,
I got a problem to code it. The principle is understood, but I am not able to get to the code.

See the picture below:
First I draw the long line going up (angle and length are different every time, depending on some input parameters, but it's not parallel to any axis).
Next I would like to draw the two lines left and right, parallel to the red axis.
Then I would liek to draw more line to make it two rectangles and
that rectangle I would like to extrude for some mm.

But I am already stuck at finding out, how to make these first two lines,
at 90° and parallel to the red axis.

Jim

If the long line "is not parallel to any axis" then the 2 lines left and right can not be both perpendicular to the long line and parallel to the red axis. The 2 lines left and right must be either perpendicular to the long line OR parallel to the red axis, but not both.

Do you mean you want the 2 lines left and right to be perpendicular to the long line and parallel to the ground plane?

Jim

Hopfully this is helpful:


model = Sketchup.active_model

line = model.selection[0]

w = 2.0
l = 1.0

pts = [
  [-w/2 , -l/2 ] ,
  [w/2  , -l/2 ] ,
  [w/2  , 0  ] ,
  [-w/2 , 0  ]
]

z_axis = line.end.position - line.start.position

l_len = z_axis.length
z_axis.normalize!

if z_axis == Z_AXIS or z_axis == Z_AXIS.reverse
  x_axis = z_axis.cross(Y_AXIS).normalize
else
  x_axis = z_axis.cross(Z_AXIS).normalize
end

y_axis = x_axis.cross(z_axis).normalize

tr = Geom;;Transformation.axes(line.start.position, x_axis, y_axis, z_axis)
pts.map!{|pt| pt.transform!(tr)}

face = model.entities.add_face(pts)
face.reverse!
face.pushpull(l_len)

mykape

Hello Jim,
this is great, thank you very, very much! I see a long way of
learning ahead of me
I can continue with my program now!

However, just out of curiosity:
Why do I need to use a different axis for the cross product
if the selected line is very steep, or rather why
exactly 1/64th is the true/false - point? Testing it,
the extruded from flips by 90°, but I can't get my
head around it - why?

Best regards and thanks again!
Klaus

Jim

The 1/64 I may have made up, or borrowed from the AutoCAD arbitray axes formula. It is probably not needed. It should work to simply compare the line to the Z_AXIS. If the line is the Z_AXIS, we need to use another axis in the cross product calculation.

mykape

Ah! ok, then I understand it.
Thanks again!