Manual

The first thing to do is to include this macro in your source file, before calling it.
When you need to create a tyre, call the macro, providing its eight parameters:

Tyre( R, Rint, Ep, Fm, Em, Hbase, Htop, k_lathe )

The above parameters have the following meaning (see figure below):

• R is the tyre radius, not including carved parts.
• Rint is the tyre inner radius, ie. the rim radius.
• Ep is the tyre thickness as seen at the carvings or rim level.
• Fm is the name of the PNG file describing the treads (see below).
• Em is the total thickness of the carvings.
• Hbase is the dradius difference between the depth of carvings at the center or outside of the tyre.
• Htop is the dradius difference between the exterior of carvings at the center or outside of the tyre.
• k_lathe is a non-dimensional parameter allowing to "inflate" the sides of the tyre. A null value gives a cylindrical value, while a value of 0.1 gives good results.

Treads description

The trickiest part. The files describes in a similar way as a height_field, the shape of treads. A black and white picture is suitable here. The darker the colour, the closer to the outside the surface gets. The tyre would print the darkest areas on a hard ground while rolling, while the brightest areas would not appear.

The picture must be horizontal, using any scale, while keeping the same proportions as the real shape would certainly make things easier.

Be careful: the isosurface code used makes it mandatory to have white pixels on the upper and lower lines. A single pixel width is enough, but must be present.

Download

You will find below a zip archive including the macro file, this documentation and an example.

tyre.zip [65 kb]