Intro

For those of you who haven't already tried it out, the No Limits Tunnel Maker is a handy little tool created by Jennifer "Tia" Lynn to create tunnels with a custom shape. Depending on where you download it from, the program will have a number of pre-made tunnel shapes. While these pre-made shapes may be neat to try out, the real power of the program is in creating your own.

Without the No Limits Tunnel Maker, you would have to convert your ride spline to python script that defines bezier curves in Blender. Then you would have to create a tunnel block, apply array and curve deform modifiers on it, and then move your tunnel along the spline until it is positioned as you see fit. After exporting to .3ds format, you aren't done yet, because No Limits won't be able to read the file unless you import and export it from another program like Anim8tor.

It's difficult to appreciate how much time the Tunnel Maker saves until you've tried to make custom tunnels without it. Even though it isn't the most intuitive of programs, it is well worth learning how to use.

The Basics

To begin creating a custom tunnel shape, click the "New Tunnel Shape" button which looks like a piece of paper. Click where you want the first vertex of your tunnel to be. When you do so, 2 points will appear. A blue point will be placed exactly where you clicked, and a green point will be placed near it. The blue point is a vertex belonging to the interior wall, and the green point is a vertex belonging to the exterior wall.

After a point is created, it can be moved by clicking it and dragging. To make your movements snap to a grid, click the right-most button which shows 4 arrows pointing at a point. The distance between snapping points can be adjusted by typing a number into the entry box next to the "Snap" button. When creating a tunnel shape for a sit-down coaster, note that the lone, white, "origin" point is the center of the track and level with the two rails. Typically, the bottom of the track spine will be 1 unit below the "origin" point, but it varies by track type.

Important!

A unavoidable fact about the ancient .3ds file format is that meshes can only be made up of triangles; no quads, no quints, no n-gons. In the case of creating a tunnel shape, your tunnel wall is made up of several quadrilaterals. In the export process, these quads must be cut with an extra line segment to form twice as many triangles. Each exterior point should be joined to one and only one interior point with a gray line segment. When the export process converts the quads to triangles, it draws the extra segment from each exterior point to one of the two adjacent interior points (either of the two points that it is not connected to by the gray line segment). Which one it chooses depends on if you constructed the tunnel clockwise or counter-clockwise. In the animation at right, most of the possible segments intersect the open area (inside the blue-segment-bordered polygon) that represents the inside of the tunnel.

To insert vertices, click on a vertex adjacent to the space that you want to add a vertex Then, press 'I' or click on the "Insert Node" button. The side of the selected vertex that the insert node feature will place the node will depend on the direction (clockwise or counter-clockwise) that the tunnel shape was constructed.

To ensure that all intersection problems are avoided, you must make sure that for each inside wall vertex, its corresponding outside wall vertex falls inside the region created by the two lines which can be drawn between the given inside vertex and its two adjacent vertices. Hopefully this image is less confusing than that explanation.

Extras

Just as the .nltrack to .3ds conversion tool of the No Limits Object Creator can be used in various creative ways, the Tunnel Maker can be used to extruded any 2d shape along a 3d curve. You could, for example, make an ionic column tunnel shape and then extrude that along a curve (roller coaster track) that twists a few times.

Another neat thing that you can do with objects from the tunnel maker is use them with 3ds terrain in Google Sketchup Free Edition or the free student edition of Autodesk 3ds Max to avoid the crash-into-the-ground effect that you get when diving under No Limits generated ground. You can export the .3ds terrain from the No Limits Object Creator and use the 3d editing program of your choice to cut a hole through the terrain at the intersection of it and your Tunnel Maker generated tunnels. In the picture at left, I'm doing just that.

Notes

When you export your tunnels from the Tunnel Maker, ALWAYS make a backup of your .nltrack file.

The "Place the object in my track for me" option does not work all the time and it will occasionally give you an "invalid references" error.

To place the .3ds file manually, first go to Options>>Preferences... and make sure "Auto Center" and "Auto Scale" are unchecked. Then, place your object dead center on the gray cross in the center of the map as low as possible.

Only check the "Remove Tunnel Flags" option if you either made a backup of your track or if you are positive that you are generating tunnels for the final time.

The object exporter will uncheck "Improved Friction" in your Coaster>>Settings... menu. If your train suddenly fails to crest a hill, this is why. The setting will be changed whether or not you tell the exporter to do anything which would involve altering the .nltrack file.

You may want to make sure that your tunnel passes the Tunnel Test.

If you have any questions about the Tunnel Maker, feel free to comment below, PM me on the forums, or email me at kevin.dice1@gmail.com.

Happy Tunnelling!