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Shawncfer

Sweep tool

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Hello all!

I'm having a little trouble with the sweep command. This is probably a stupid question with an easy answer, but I'm stuck and frustrated!

I set my view to 'Front', draw a NURBS curve like an arc. Set a locus point at the top right corner, select both, and Sweep.

Then I get "The objects being operated on must be in the same plane."

I'll be honest, I semi-understand the working planes thing, but not totally. So any help would be much appreciated!

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Not a stupid question at all.

1. The sweep command doesn't work on nurbs curves. You can use any 2D geometry. Like a polyline, line polygon, rectangle, circle - whatever.

2. Select the arc and the locus. In the OIP set the Plane pulldown to screen or layer. If you are in a front view, you probably want screen plane.

To confuse you even more, neither the layer plane or the screen plane are a working plane. Working planes are set with the working plane tool.

The plane thing can be confusing at first. This is a really simplified explanation. Probably with errors.

Screen Plane: no matter what view the drawing is in, the screen plane is the plane of your computer monitor. Changing the view of the drawing does not affect screen plane objects. You might want to use a screen plane to guarantee that an extrude will be normal the the view you are currently in.

Layer Plane: The "ground" of the current design layer. It's Z height is controlled in layer organization.

Working Plane: A user defined plane - usually relative to some geometry in the drawing. Imagine placing something on a sloped roof face normal to the roof face rather than perpendicular to the earth. You could set up a working plane defined by the roof face to make it easier to work on.

hth

mk

Edited by michaelk

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Awesome! Thanks Michael!

So I were drawing the roof of a dome, for example, it obviously has some thickness to it, it's not just flat. Is it safe to assume that if I want my sweep to have some thickness like a roof, I just draw the original object like a polygon, and then sweep it? Instead of just drawing an arc?

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Exactly.

You can draw just one side, say the outside of the dome. Then use the offset tool (with Close Open Curves selected) to create a polyline with the perfect thickness.

hth

mk

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When using the sweep command, be very aware of the segment angle. Vectorworks sets it to a very small angle, making a sweep very resource heavy. A small segment angle may be necessary for very large diameter sweeps, but more often than not you can get away with a larger sweep angle, saving you valuable processing power.

KM

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Very true. VW sweeps default to 0.70 degree segments. Probably perfect if you are sweeping a wristwatch crystal.

But the dome of a building can be much higher than that. I rarely use a segment value less than 10 degrees. Usually higher. Make it as high as you can stand it to keep processor overhead down.

mk

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FYI the default sweep angle depends on the VW prefs->3D->3D conversion res value. Set this to Low or Medium instead of High or Very High to get a lower increment angle for new sweeps.

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Now that's really interesting to know. I always assumed that when I changed the 3D conversion res value, all the 3D objects in a file were rebuilt using the new value. Am I wrong in assuming this is what it does?

I didn't know it directly affected a value that once set, never changed again automatically. This leads me to a wish for the sweep, a check box that says "adjust dynamically to reflect 3D conversion res value".

Just as Michael, I would never use a segment value less than 5 or 10 degrees.

Kevin

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So let me also ask you guys this:

Back to the dome reference. Let's say I wanted to make the roof of a football field, that's more of an oval shape. How would I accomplish that?

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I would approach it using NURBS curves, most likely using the "Revolve with Rail" command (Model Menu>3D Powerpack>Revolve with Rail). The command requires 3 objects -

- a vertical NURBS "curve" (I put curve in quotes because its actually a straight line converted to NURBS or a NURBS curve drawn using a degree of one which means its straight)

- a rail curve, in your example the oval converted to a NURBS curve

- a profile curve which could be your existing profile you used for the sweep, also converted to a NURBS.

Centre the vertical axis in your oval, align your profile with the axis and the edge of your oval and choose the menu command. Select the axis, profile and rail in that order.

Kevin

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Or just a simple loft in among ribs. Probably need to do quarters or other partials so the loft will work.

-B

ubbthreads.php?ubb=download&Number=8417&filename=EndView.png

ubbthreads.php?ubb=download&Number=8418&filename=WireFrame.png

ubbthreads.php?ubb=download&Number=8419&filename=OGL.png

Edited by Benson Shaw

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Here it is lofted one end instead of one quarter. Shelled the loft segments. OGL is set to draw edges, hence all the "contours".

-B

ubbthreads.php?ubb=download&Number=8420&filename=1:2%20dome%20Shelled.png

Edited by Benson Shaw

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Kevin!

I'm trying it your way first and am having a little bit of trouble. In plan view, I drew an oval. I then drew a line from the center of the oval directly up to the height I wanted of the dome. Then drew and 'arc' connecting one of the midpoints of the oval to the top of the line. Finally I converted all of which to NURBS curves. But when I go to 'Revolve with Rail', I'm allowed to select the axis, but when I select the profile curve, I get an error message.

Here are a couple of photos (The line through the middle of the oval was so I could find the center point of the vertical line).

nexrbn.jpg

5k0ubb.jpg

35colk4.png

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Shawncfer - Something to test - redraw your axis and profile to be sure of all of the following from VW Help:

<

To create a NURBS surface with profile and rail:

Create the axis, rail and profile out of NURBS curves.

Conditions must meet the following requirements:

● The axis must be a linear NURBS curve

● The profile must be a planar NURBS curve

● The profile cannot intersect the axis, though it can touch

● The axis must lie on the same plane as the profile

● The rail must be a planar NURBS curve that lies on a plane perpendicular to the plane containing the axis and profile

Select Model > 3D Power Pack > Revolve with Rail. Select, in order, the axis, profile, and rail.

/>

Click order is important, too:

Axis, then Profile, then Rail

Your setup looks like it should work. Something must be out of plane or not touching or intersecting or something.

Maybe try drawing your axis and/or profile with the NURBS curve and NURBS arc tools instead of conversions from 2d.

-B

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Well, I deleted the profile, redrew it as an arc again, converted to NURBS, and it works perfect. I have no idea what I did wrong in the beginning, but it works perfect now.

So my next (hopefully final) question is, how would I give the 'roof' some thickness?

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For uniform thickness

Shell tool in the 3d tool set. Works really well with the Revolved object. Also, the OIP of the Shell can control the oval aspect and the height of the shell, as well as its thickness.

For non uniform thickness,

A. Duplicate in place and adjust the OIP parameters of the new surface. (leaves you with unconnected inner and outer surfaces)

or

B. Create a new profile and new rail (or several of each if different areas have different thicknesses), and revolve again.

If A or B needs a single, shell-like volume, extract the bottom edges of inner and outer surfaces, loft them (creates a horse track oval band). The 3 surfaces can be added to make a solid addition.

-B

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