Part 2: Intersecting and Trimming

A common way to combine NURBS surfaces is to intersect the surfaces, then trim them where the two surfaces cross each other. This is the approach you will take with the upper and lower surfaces of the vacuum cleaner.

First, you will intersect the surfaces. When you intersect surfaces, you create curves-on-surface, which are lines that are created on the surfaces where the surfaces intersect. You will then trim the intersecting surfaces along the curves-on-surface, so the unnecessary surface areas are discarded, and only the necessary surface areas remain.

Opening the tutorial file (optional)

If you successfully completed Part 1, you can proceed directly to the next step, Intersecting the upper and lower surfaces.

If you were not successful in part 1, open the file called vacuum_part2.wire, located in the wire directory of the CourseWare project. This file contains the completed model from Part 1.

Watch Part 2 of the tutorial.

Intersecting the upper and lower surfaces

Now, you will intersect the upper and lower surfaces to create the body shape.

Click the wireframe icon in the diagnostic Shading area of the Control Panel to remove the shading.
Choose Surface Edit > Create CurvesOnSurface > Intersect . This tool creates the curves-on-surface that are used to trim the surfaces.
You are prompted to select the surface(s) to intersect.
Use the to click the upper surface to select it.

The surface is highlighted and a Go box appears in the lower right corner of the view.

Click the Go box to select the first surface to be intersected.

The surface is highlighted in pink.
You are prompted to select the intersecting surface.
Click the lower surface to intersect it with the upper surface.

The surfaces are intersected. Two curves-on-surface are created, one on each surface.

By default, the Intersect tool creates a curve-on-surface on each surface so each surface can be trimmed.

Both surfaces are now drawn with a dotted outline to indicate that each has a curve-on-surface.
Choose Pick > Object Types > Curve on Surface .
Drag a pick box around the intersected surfaces to pick the curves-on-surface.

The highlighted curves that appear are the two curves-on-surface. It looks as though there is only one curve-on-surface, but in fact there are two in the same location, one on the upper surface, and one on the lower surface.
Choose Pick > Nothing to unpick the curves-on-surface.

Trimming the surfaces

Now, you will trim off the excess from the upper and lower surfaces.

NoteA trimmed surface is not actually cut; it exists in a hidden form that does not render or affect modeling. While performing a trim, you can easily discard part of a trimmed surface by selecting the unwanted portion of the geometry and clicking the Divide

button that appears at the bottom right corner of the screen.

Choose Surface Edit > Trim > Trim Surface .
You are prompted to select a surface to trim.
Pick the upper surface.
You are then prompted to select one of the following:
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Shift select to select surfaces or click to select REGIONS.
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The last option allows you to trim away the excess parts of the surface, so this is the prompt you will respond to.

Click any part of the upper surface on the inside part that you want to keep.

The Trim tool places an indicator where you clicked and an option box appears in the bottom right corner of the view.
Click the Keep button.

The upper surface is trimmed.
Repeat steps 1 – 4 to trim the lower surface.

Creating the nozzle surface

Next, you will create a planar surface across the mouth of the nozzle, to complete the exterior shape of the vacuum body.

1 Choose the Surfaces > Planar Surfaces > Set Planar tool.
You are prompted to select a curve.
Click the straight-line curve along the center grid line to select it as the first curve for the planar surface.

The curve is selected and a Go button appears in the bottom right corner of the view.

You are prompted to select another curve.
Click the front nozzle curve to select it as the second curve for the planar surface. If the pick chooser appears, make sure that you pick the curve, not the surface edge.

The curve is selected, and you are prompted to select another curve.
Click the rear nozzle curve to select it as the third curve for the planar surface.

The curve is selected. The three curves form a closed region within which the planar surface will be created.
Click Go to create the planar surface.

The surface is created and highlighted in pale yellow.
Choose Pick > Nothing to deselect the planar surface.
Use diagnostic Shading in the Control Panel to view the model.