How the Spin Tool WorksEdit
The Spin tool works by making copies of the selected vertices in a radial array around an axis indicated by the 3d cursor. Each copies of vertices are connected to previous vertices that corresponds to it with necessary geometry, i.e. edges and planes.
A picture explains this more clearly.
Note that the copied vertices are arranged in a radial array around our 3d cursor and parallel to our view plane.
Typical Work FlowEdit
1) Make half of the outline of our object with connected vertices. If you want to model a wineglass, make the half of the outline of the wineglass.
2) Spin our outline. After this the Spin tool would complete our object.
3) Clean up the resulting mesh. The mesh created by the Spin tool is not so perfect so we had to "clean" it up.
Modeling Half of the OutlineEdit
To start we make half of the outline. Here we do it by creating vertices.
Open Blender. Don't remove the default cube cause we are going to use it. If you don't have any object after you open Blender (like mine), add a mesh object. Any of them will do. I tend to use the plane. At this time it is good to give your object a proper name. Name it sensibly, like "wineglass" if we are modeling a wineglass. This will help us locate it if there comes a time when we have a lot of objects in our scene. We don't want to have all objects to be called cube.001, sphere.003 or something. That could get confusing.
Hit Tab key to enter Edit Mode, if we are not in there yet. Select all vertices by hitting AKey, then delete them with XKey -> Vertices. Then go to the front view be hitting Num1.
Now, we are going to make the outline by creating vertices. Press and hold CtrlKey then click the left mouse button. A new vertex would be created. Click the left mouse button again, another vertici would be created but this time it is connected to the previous vertici by an edge. Click again to add more vertices. We are going to use this to create our outline.
You might notice that the 3d manipulator (red, green and blue arrows) could get in the way. Deactivate it by hitting Ctrl+Space Bar, then select Enable/Disable, or by clicking the white pointing hand icon in the 3d view window.
Lets start making the outline. Delete our previously created vertices first. Using what we have learned, lets create vertices again but this time lets add them to form some sort of outline. let us be creative here. It could be anything you want. Here I make two to illustrate two situations that we might encounter when modeling with the Spin tool. That is modeling objects that are hollow or non hollow.
Here, the first one, is an outline of a glass. Here, we are modeling an object that is not hollow. We had two vertices that are located in the center of our would be glass bottom. We need to align the two central vertices perfectly along the z axis. Select this two vertices then scale it along the x axis to zero (SKey, xKey, 0Key, Enter).
The second one I will make into a napkin ring. This time our outline is closed and no vertices are located in the center of our would be napkin ring. Here we are modeling an object that is hollow.
To make the closed outline, select the two vertices on the open side then press FKey. The two vertices would be bridged by an edge, thus closing the outline.
Adjust vertices when necessary.
For those who may like to have an image in the background to guide them. Upload a background image by selecting the View menu from the 3d View Window then select "Background Image". A new internal window would appear. Click "Use Background Image" Button, then click "Load". Navigate to where the Image is located select it then click "SELECT IMAGE". Our image would appear on the 3d Window as a background. Bellow, I used a picture of a wineglass.
Spinning Our OutlineEdit
Now that the outline is finished, we are ready to use it with the Spin tool
Two things you must know is that the Spin tool is dependent on the location of the 3d cursor, and view where we activate our Spin tool.
Here is our setup with the vertices all selected. In the nest pictures are results when this shape is spun with the 3d cursor at different locations.
Here we have the same shape but is spun around in different views.
Note that its important only to place the 3d cursor properly relative to the view where you are going to use the Spin tool
Placing Our 3d CursorEdit
We can see that the location of our 3d cursor is very important in Spin modeling so we need to know how to place it properly. If you prepare it to be, the cursor would already be in position after we make our outline but accidents happen and we accidentally misplaced our 3d cursor. Here are some ways we could make our 3d cursor go to the place where we want it to be.
Snapping the 3D cursor is a quick and simple way to place our 3d cursor to its proper location. In the 3d window, hit Shift + SKey. A list of options would appear. We are interested with the last three options, namely the cursor snaps options. They are the Cursor->Selection, Cursor->Grid and Cursor->Active. The name are pretty descriptive but we'll give a short description here.
Cursor->Selection places the cursor to the exact location of our selected element or elements. In case of multiple selected elements, our cursor is placed on the median of the selected elements. In edit mode, select a vertex and use Cursor->Selection snap to it. Our 3d cursor would jump to the exact place where our selected vertex is located.
Cursor->Selection snapping is especially useful when modeling non hollow objects because there are vertex or vertices located at the center of our model to snap to. Just select one central vertex and snap to it.
Cursor->Grid snaps the cursor to the nearest cross of the visible grid. Try clicking at a center of a square in our Blender's grid and use it. See its effect.
Cursor->Grid snapping is useful for spin modeling hollow models. Usually if you are careful, our object outline would be on a plane that contains one of the axises. If we make our outline in front view as advised, go to the top view (or side view depending on what we are modeling). If you are doing okay, you will see all our vertices aligned perfectly along the x axis. It just a matter of LMB close to a cross on the grid that contains our objects center then snap to it.
Cursor->Active might not be so helpful in spin modeling. Cursor->Active snaps the cursor to the active element (usually the element that is last to be selected). Try it by selecting several vertices, then do Cursor->Active snap. The vertex where the 3d cursor goes is the active element in your selection.
Spin Tool ParametersEdit
The spin accepts two parameters to execute its function. These are Degrees (degr) and Steps.
Degrees specifies the angle at which the selected geometry will be rotated from its initial position around the axis. It accepts values in degrees. A 360 degrees value being a whole turn around the axis. Values lesser than 360 produces something like a wedge is sliced from the side of the form.
|Sample Outline Spun with Degress parameter set at 245 degrees|
|Sample Outline Spun with Degress parameter set at 360 degrees|
Steps specifies the number of "copies" of the selected geometry the spin tool makes that it arranges in a radial array around the 3d cursor. A higher value result in much rounder form.
|Sample Outline Spun with Steps parameter set at 4 steps|
|Sample Outline Spun with Steps parameter set at 32 steps|
Cleaning Up the resulting MeshEdit
After using the spin tool, a little up work might be necessary, especially if you specified a 360 degree turn. Though the mesh looks clean to the eye, the tool actually make geometries (vertices) that are in the same blender position as another one. So what might look like one vertex may actually be two. A simple way to clean up our mesh would be to select the whole geometry then activating the "remove doubles" from the specials menu ( Wkey(Specials Menu) -> remove doubles or Wkey->6key). This would remove these problem geometries, finds vertices that are too close to each other and merging them to one.
After the lathe able parts are done it would be ready to adding non latheable parts. For example a cup may have a bowl-like body, that we could use the spintool. Alas the handle can't be so we had to put it there after. Depending on the geometry added. This geometries could be formed from the mesh itself or be adding in a separate mesh.