Spin Modeling

On January 13, 2008, in Uncategorized, by Admin

Here is a simple and easy tutorial on modeling an object using the “Spin” function. Any
object that is symmetrical around can be modeled this way. It could be a glass, a jar,
a vase, a column, a post, a wheel or anything.

The first thing I always do, from the Front View (1), is to add a plane. I’m going to model a glass
goblet for this tutorial. Select 3 out of the 4 vertices and delete them. For my glass, I’m going
to imagine that this remaining vertex is the very center of the bottom of the base. Select that
one vertex and begin extruding out (E) forming the out line of your object.

We want to trace the outline of our object as if it was cut in half by a laser beam. We only need
to trace one side. In my case, it’s the right side of my glass. Here I have the base, the stem
and the beginning of the body of the glass.

Here is my completed outline. Just the right side of the cross section of my glass.

The next step is to align the 2 vertices that will be in the center of our glass. One is
in the base and the other one is in the bottom of the body of my glass. Select just those two
vertices. Press S for Scale, X to scale along the X axis (You should still be in front view so the X axis
will be from left to right) and press 0 (zero) so they will line up exactly on the X axis.

Now we’re ready to spin our glass. To do this, the first thing we need to do is get our 3D Cursor
in the correct location. When you perform the Spin Function, your objects will rotate around the
3D cursor where ever it is. We want our vertices to spin around the center of our object. We
now have 2 vertices that are in the exact center of our object, the 2 that we just aligned. To get
your cursor there, select one of the vertices in the center of your model and press
SHFT-S. Select Cursor -> Selection

That puts our 3D cursor exactly in the center of our model. Perfect!

Switch to over head view here (7). The other thing to remember when ‘Spinning’ a model is that
Blender will spin the selected objects based on the current point of view. If you’re looking from
the front view, it will rotate the selected objects around the X and Z axis (Up/Down and Left/Right).
We want to spin our glass around it’s center based on the way we drew it, we need to be looking down
at it.

While still in edit mode, make sure you still have all of your vertices selected. Under the Mesh Tools
tab you’ll fine the controls we need to spin the model. We’re going to use the Spin button. The
default is set to 90 degrees, 9 steps and 1 turn.

If we click Spin with those settings, what we end up with is 1/4 of a glass. Press CTRL-Z to undo
that and change the Degrees number to 360 so it will go all the way around. The Steps value determines
how many times during the rotation Blender will stop and make a copy of our vertices. In the 1/4 glass, we
had 9 copies of our vertices.

In the full glass, we still ended up with 9 copies of our vertices, they were just spread out farther apart
during the rotation. The more steps have, the finer the detail of the spin will be. 4 steps around 360 degrees
would gives us a square glass.

Now, we need to get rid of the extra vertices. The last step of the 360 degree rotation always
ends up on top of the original vertices. Select all of your vertices.

Press W and select remove doubles to remove any vertices that ended up on top of other vertices. Blender
will give you a count of the number of vertices removed.

Since we started with an open object and created a closed object, let’s turn on the surface normals
to check that they are all going in the right direction (Not facing the inside of our glass).

While in edit mode, under Mesh Tools 1, you’ll find the button that will turn on the surface normals. The
value above it adjusts the size of the blue line that represents the surface normal. Everything
appears ok.

I’m going to add Sub Surfacing to my glass to help smooth it out. While still in Edit mode,
locate the Modifiers tab.

Click the Add Modifier button and select the SubSurf option.

Here’s a test render of my glass with SubSurf turned on.

Next, I’m going to turn on the Set Smooth option. With our glass selected in Edit mode, locate the Link
and Materials
Tab. Click the Set Smooth button.

Switching from Edit to Object mode, we can see a definite problem. Those black sections in our
object are an obvious sign that we have some surface normals facing the wrong direction.

Switch back to Edit mode, select all of your vertices (press A until all of them are selected)
and press CTRL-N. Click Recalculate Normals outside to fix our problem.

That smoothed every thing out.

I’m going to go ahead and give my goblet a nice purple glass texture.
Here are the settings I used to make the glass texture. The default depth was set at
2 (under the mirror transp tab) which was not enough so I increased it to 3. Depth determines how many times the
computer will trace light rays through transparent objects and off of reflective surfaces.

The settings for my ground Plane’s material. In order for my ground plane to receive some
of the light coming through the glass, I needed to turn on the TraShadow button. That way,
the transparent shadows coming through my glass will show up on my ground plane instead of just
a solid shadow as if the goblet was made out of something not transparent.
Good luck with your modeling.Scott

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