1.7.7.4. Spin

Reference

Mode: Edit Mode
Panel: Tool Shelf ‣ Tools ‣ Mesh Tools ‣ Add: Spin
Hotkey: Alt-R

The Spin tool extrudes (or duplicates if it the selection is manifold) the selected elements, rotating around a specific point and axis.

Use the tool to create the sort of objects that you would produce on a lathe (this tool is often called a "lathe"-tool or a "sweep"-tool in the literature, for this reason). In fact, it does a sort of circular extrusion of your selected elements, centered on the 3D cursor, and around the axis perpendicular to the working view...

  • The point of view will determine around which axis the extrusion spins...
  • The position of the 3D cursor will be the center of the rotation.

1.7.7.4.1. Options

Steps
Specifies how many copies will be extruded along the "sweep".
Dupli
When enabled, will keep the original selected elements as separated islands in the mesh (i.e. unlinked to the result of the spin extrusion).
Angle
Specifies the angle "swept" by this tool, in degrees (e.g. set it to 180 for half a turn).
Center
Specifies the center of the spin. By default it uses the cursor position.
Axis
Specify the spin axis as a vector. By default it uses the view axis (viewport).

1.7.7.4.2. Example

_images/spin1.png

Figure 1: Glass profile.

First, create a mesh representing the profile of your object. If you are modeling a hollow object, it is a good idea to thicken the outline. Fig. Glass profile. shows the profile for a wine glass we will model as a demonstration.

Go to the Edit Mode and select all the vertices of the Profile with A.

We will be rotating the object around the cursor in the top view, so switch to the top view with Numpad7.

_images/spin2.png

Figure 2: Glass profile, top view in Edit Mode, just before spinning.

Place the cursor along the center of the profile by selecting one of the vertices along the center, and snapping the 3D cursor to that location with Mesh ‣ Cursor ‣ Selection. (Fig. Glass profile, top view in Edit Mode, just before spinning.) shows the wine glass profile from top view, with the cursor correctly positioned.

Click the Spin button. If you have more than one 3D View open, the cursor will change to an arrow with a question mark and you will have to click in the area containing the top view before continuing. If you have only one 3D View open, the spin will happen immediately. Fig. Spun profile. shows the result of a successful spin.

1.7.7.4.3. Angle

Spun profile.
_images/spin3.png

Figure 3: Spun profile using an angle of 360.

_images/spin4.png

Figure 4: Spun profile using an angle of 120.

1.7.7.4.4. Dupli

_images/spin6.png

Figure 5: Result of spin operation.

_images/spin7.png

Figure 6: Result of Dupli enabled.

1.7.7.4.5. Merge Duplicates

_images/spin8.png

Figure 7: Duplicate vertices.

The spin operation leaves duplicate vertices along the profile. You can select all vertices at the seam with Box select B shown in Fig. Duplicate vertices. Seam vertex selection and perform a Remove Doubles operation.

Notice the selected vertex count before and after the Remove Doubles operation Vertex count after removing doubles. If all goes well, the final vertex count (38 in this example) should match the number of the original profile noted in Mesh data ‣ Vertex and face numbers. If not, some vertices were missed and you will need to weld them manually. Or, worse, too many vertices will have been merged.

Note

Merging two vertices in one

To merge (weld) two vertices together, select both of them by Shift-RMB clicking on them. Press S to start scaling and hold down Ctrl while scaling to scale the points down to 0 units in the X, Y and Z axis. LMB to complete the scaling operation and click the Remove Doubles button in the Tool shelf in Edit Mode (also available with Specials ‣ Remove Doubles).

Alternatively, you can use Specials ‣ Merge from the same Specials menu (or Alt-M). Then, in the new pop-up menu, choose whether the merged vertex will be at the center of the selected vertices or at the 3D cursor. The first choice is better in our case!

1.7.7.4.6. Recalculate Normals

All that remains now is to recalculate the normals to the outside by selecting all vertices, pressing Ctrl-N and validating Recalc Normals Outside in the pop-up menu.