Create a cone frustum in Sketchup using Ruby

Developers Ruby API
1

I need to create a conic frustum in Ruby in SketchUp.

By hand in the GUI, this is easily accomplished by creating a circle, doing a push-pull to get a cylinder, and then choosing a point on the top of the cylinder and "move"ing it along the X-axis to adjust the top circular face radius.

Using the Ruby API, I can’t quite figure out how to grab the point on the top circular face and move it along the X-axis.

Here’s my code so far:

#Create cylinder
pt1 = Geom::Point3d.new(0, 0, heightToLayerBottom)
vt1 = Geom::Vector3d.new(0, 0, 1)
model.start_operation “Cylinder”
numSides = 96
edges = entities.add_circle(pt1, vt1, bottomRadius, numSides)
face = entities.add_face edges
layerHeight = -layerHeight if( face.normal.dot(Z_AXIS) < 0 ) #Guarantees this goes “up” the Z-axis
face.pushpull layerHeight

Now, however, I don’t know how to proceed. I need to get the top face, get the point on this face that intersects with the X-axis, and then move this point along the X-axis a predetermined distance to change the diameter of the top face.

For this case, I will always have a bottom and top face circle centered at (0,0) for X and Y, with a vertical (Z) push-pull cylinder.

Can anyone help?
Thanks,
Madeleine.

2

Go to the Extension Warehouse and install the SketchUp Team’s example Shapes extension. Look at how they create a Cone.

http://extensions.sketchup.com/en/content/shapes

3

I’m not a great Ruby programmer, but I think that if you can identify the top face in Ruby, you could use a Scale transform to scale the top face uniformly about its centre, in the x - y plane.

See API docs for Geom::Transformation.scaling

4

Yes that could work, as well as drawing a half section profile, and a reference circle, calling the followme method.
http://www.sketchup.com/intl/en/developer/docs/ourdoc/face#followme

5

finding the top face is trivial if you know the context and you know the height…

you do if you made them, but make everything in a group to guarantee context …

top_face = cyl_grp_ents.grep(Sketchup::Face) { |f| f if f.bounds.center.z == height }.compact!

# possibly even 
 top_face = cyl_grp_ents.grep(Sketchup::Face)[-1]

john