by Jason Elam
This tool is very versatile and can be used for a variety of applications. You can use it to create just about anything with a curved shape to it. In my examples I will show you how to create a roller coaster track and a children's slide.
The rail extrude tool can be found under the 'MULTIPLY' tab or by hitting ^R on the keyboard. (control shift R)
You must have at least 2 layers, the first is the curve that you want the object you are extruding to follow. The other is, of course, the object. You must then select the object to be extruded as the active layer. The curve should then be the background layer.
We will start with a demonstration of how to make a simple children's slide.
First use your sketch tool to create a curve that the object will be extruded along. I have created this curve in the shape of a slide.
Once you have create your curve, you can move on to another layer to create the shape that will be extruded. I made this shape by merely subdividing a simple box and then moving the points in from the corners and the points in the center down to create the groove of the slide.
Finally the next step you are ready to use the Rail Extrude tool. Find this tool under the multiply tab. Set the segments to 'automatic'. This will create a new segment wherever the tool deems appropriate. This is usually a good idea because otherwise you may end up with "blocky" looking shapes. Depending on what you are trying to do though automatic will help to keep your shape smooth, but may add more polygons than you consider necessary. Having the 'oriented' box checked will help to ensure that the shape you are extruding stays facing perpendicular to the curve as it is extruded. I will later show an example of what happens if the 'oriented box' is unchecked. Once you have the correct settings hit 'ok'.
You should end up with something like this. Take note that I have moved the object away from the curve it was extruded along to show the relationship.
Now I will demonstrate how to create a simple roller coaster track.
First create the basic shape of the track with a simple sketch. Use other tools to bend, stretch, and postion the track as you would like. Then create a small disc and place it at the edge of the curve.
Select the Rail Extrude tool just as before and use the same settings.
And you have your track!
Now I will show you what would happen if you weren't to use the 'oriented' option on the roller coaster track.
The disc shape will be extruded along the curve but without rotating as it extrudes. This will result in a flat shape throughout and will not produce the consistant round shape that would be desired when creating a roller coaster track. This is demonstrated by the orientation of the red lines.
Rail Extrude can be used to make more complex shapes that involved one shape being extruded along multiple curves simultaneously. This can be used to create an object in which the desired result is not a uniform type object that I have demonstrated here.
Have fun using this versatile tool to simplify your creation of objects.