Lathe Tool Pointers
By
Kevin Alvarado

The purpose of this tutorial is to help explain the Lathe tool within Lightwave.  You might consider this traffic report on the tool to help you avoid accidents and bumps in the road.

First I’d like to help you gain an understanding of what a lathe is.  In woodworking, a lathe is “a machine in which work is rotated about a horizontal axis and shaped by a fixed tool” (Webster’s Dictionary).  Basically a wood worker would have a piece of wood spinning while carving out the edges of that wood; because of the rotation each carve would circle the wood giving it its new shape.  The effect would be similar to creating a ceramic vase on a wheel, except the wood would spin on its side instead of vertically.

Here are some examples of objects that can be created using the lathe tool.
This Scene was created entirely with objects created with the lathe tool.

 Final Image

To start:
To begin with, you need to have something to lathe.  The tool needs some object to work with, be it a point, a single edge, curve or a polygon. 
ROAD BUMP: You can pretty much use an object of any type, however, in my experience, using anything outside of two dimensions may have unpredictable results.

We’ll start by creating a few points and combining them to create a few line segments.  Using the ‘Points’ (+) tool left click anywhere on the screen to create your first point, <Image01> followed by a series of right clicks to create subsequent points <Image02>.  Next you’ll need to connect the points.  Select the points you wish to connect, and use the ‘Make Pol’ (p) tool <Image03><Image04>.  I would recommend selecting two at a time and hitting the (p) key.  If you select three or more points, you’ll create a triangle or polygon, which is not what we’re going for just yet.


Image 01
Image 02

Image 03
Image 04
 
ROAD BUMP:  Order of points is extremely important!  If your trying for a nice smooth shape, the order of points along your curve MUST be in the order that the points were created!  If you manage to ‘connect the dots’ out of order your lathe object will appear as if it folded in on itself.  This is due to Lightwave trying to create polygons from one point to another that are out of order.
 
Once you have your basic shape, and all points are connected <Image05>, you can now lathe the object.  You can either click on the ‘Multiply’ tab at the top of the window followed by the ‘Lathe’ (L) tool, or use the shift+L key combination <Image06>.  Next, left click at a point where you want the object’s center of rotation to be, followed by dragging the mouse (still holding the button) in the direction you want rotate around.  In our example, I clicked directly over the lowest point and dragged downward, giving us the resulting shape <Image07>.  The result is each point makes a ‘ring’ around the direction of the mouse drag giving us our axis of rotation, and the line segments we made sweep around the axis of rotation giving the object it’s shape.  It’s as if we made a clay bowl <Image08>.  Press the space bar to accept this object.

Image 05
Image 06

Image 07
Image 08
 
 
Numeric: Lathe Tool dialog box:
At this point you can press the space bar to keep this shape or we can hit the (n) key to change the numeric values that make this shape <Image09>.  Right now the important values listed are ‘Sides’, ‘Start Angle’, and ‘End Angle’.  If we alter these values, it will affect our shape accordingly.  The ‘Sides’ value, here 24, gives us 24 sides of our circle.  If I were to increase this value it would give us more sides to our circle and give us a much smoother shape, decreasing the value will make a more harsh shape.  The ‘Start’ and ‘End Angle’ values tell the tool at what angle to start and stop the sweeping of our shape.  A combined value of 0 and 360 degrees gives us one complete circle.  Any values between those will give us part of a circle.  If I were to change the values to Sides: 32, Start Angle: 45, and End Angle: 180 we would end up with 32 sections of our shape sweeping through those two angles <Image10> <Image11>.

Image 09
Image 10
Image 11
ROAD BUMP: If we were to put values larger or smaller than 0 and/or 360 degrees, say for example –25 and 450 our circle would overlap in some parts starting at angle –25 going through angle 0, passing angle 360 and continuing on until angle 450 degrees.  Values of 0 and 720 would give us two full rotations, now this will cause overlapping polygons, which is something to avoid.  You might think why would you want to do this, but I’ll go over a situation for this later.

Now I will address the other values within this dialog box. 
The ‘Axis’ value reflects the axis of rotation the object was spun around.  Change the value from Y to another value will change axis of rotation and will change the shape of our bowl, mainly because the bowl was designed to rotate around the Y axis. 
The Center values XYZ represent the center point that we are rotating about.  If we were to change these values the our shape’s center of rotation would change and our bowl would either end up with a hole at the bottom because we moved further away from the spin or it could fold in on itself in some parts because our original curve in image 5 overlaps the axis of rotation.
 
The Offset value is a bit of an advanced topic; and can be used in the situation I mentioned earlier about overlapping polygons from large angle sweeps.  Basically, the offset moves the center of rotation along the axis of rotation (mouse drag direction) either up or down, depending if the value is positive or negative.  In other words, from the start angle the curve moves up a bit for each angle until the lathe reaches the end angle at which point the end angle is the offset distance away.  It’s like a corkscrew, as you keep turning the sharp end of the corkscrew moves further away.  Using a simple shape <Image12> with an axis a bit away and changing the offset <Image13> I got this corkscrew shape <Image14>.  Notice because of the Offset value we do not have any overlapping polygons so we were able to avoid that bump in the road.

Image 12
Image 13
Image 14

 
Examples:
As I mentioned earlier, you can lathe almost any 2D shape.  Here are some examples of using point and curve creating tools other than the ‘Points’ (+) tool, along with their lathe results.
Pen Tool:

Image 15
Image 16
Sketch (`) Tool:

Image 17
Image 18
Bezier Tool:

Image 19
Image 20

Spline Draw Tool:

Image 21
Image 22

 
Conclusion:
The lathe tool is a very constructive tool that will make simple work of cylindrical objects.  Choosing the right tool to create an object is very important.  You might be able to achieve the same results using two different tools, one very quickly but the other is time intensive.  A good way to decide to use the lathe tool is to compare the object to vase and ask yourself if you could make that object on a potter’s wheel.  If that’s the case the lathe tool would probably be the best suited tool for the job.
 
One thing to watch out for is that it is very easy to get carried away with detail by increasing the ‘Sides’ within the numeric dialog box.  Remember the more points and polygons in an object the longer it will take for your scene to render.

 Final Image