I have spent the last week reworking my first track for AC, Thomson Road in Singapore. I was asked to increase the number of grid slots from 24 to 30 for online racing, and what started out as a quick fix turned into something slightly more in-depth once I took a look at the 5 year old track
The biggest difference between this track and my subsequent ones is the way I made the physical road mesh. Thomson road uses a copy of the quad-based visual road simply subdivided into tiny quads, noise added and then optimised to reduce the poly count. The problem with this method is that the edges of the quads remain in place, all in a line, even after adding the vertical noise. I find that the single contact point of AC's tyres can get hooked up on a particular row and cause a weird resonance through the FFB.
Old method on top, later method underneath.
As my later method uses tris not quads, the tyre contact point never gets chance to follow the same row, giving a much more natural feeling through the FFB.
I thought I would spend a little bit of time trying to document the process, in case it helps anyone new to track modding who happens to use 3ds max (sorry, Blender peeps).
First step is to split your visual road mesh into smaller chunks; each chunk will end up being a short section of physical road mesh. I use lots of small sections as it makes it easier to add a lot of variety to the road surface that way. Rather than the whole track feeling the same, chunk #1 could be very smooth, #2 could be slightly rougher, #3 could have a few bumps and pot holes, etc, etc.
So, take your short section of quad-based visual road:
Select the outer edge...
and convert that section into a new shape:
Go back to your quad section of visual road and extend the outside edge of it by a few centimetres, so it is slightly larger overall than it was originally. I used this free script:
http://www.scriptspot.com/3ds-max/scripts/extend-borders
Select the new spline / shape you created from the outer edge and apply a Garment modifier to it
The default values will fill the shape with only a few tris, but we want a much more dense collection of triangles to enable lots of detail in the new physical mesh. The inset pic shows the shape filled with tris that are about 25cm on each side
The Garment modifier turns the shape we created into a flat plane, so we need to make it follow the original visual road surface again. This is where the original short section comes back into play. Making sure that the Garment object is above the visual mesh, first convert it into an editable poly and then (using this script -
https://www.klaasnienhuis.nl/2011/11/align-vertices-to-a-mesh-in-3dsmax/) drop the new high-detail object onto the old visual mesh.
Without that loop of quads we added in the beginning, some of the outer verts of the new shape would miss the visual mesh and get left high: