Hi there! My name is Darío, I’m a programmer within the team of Formula Wincars. I’ve been involved in the access to the database, the race statistics and some networking aspects of the game. Although, today I’m gonna talk about the first task I had to do when I joined the team, wheel skid-marks.
The wheel skid-marks are the marks that the car leaves on the road when you slide. It may seem like they have no importance, but once you are playing skid-marks give a really good feeling. If you make the perfect realistic racing game and you don’t include skid-marks it just won’t look good. You might not be aware of what is missing, but you would know something is wrong in there. The same applies to trail-marks. Those are the marks the car leaves on the terrain.
Skid-marks and trail-marks are usually underappreciated. We wanted to make it right. To do so, we have several textures, one for each terrain and another one for road skid-marks. Once we detect that the car is sliding or is on a certain terrain we start creating new geometry at runtime and applying the correct texture to that geometry.
To create geometry at runtime is a complex process as we have to be very careful about the order we connect the different vertex, if we don’t connect them in the right order they won’t appear in the scene.
As this geometry is made over time, there will be some triangles bigger than others and so their length can vary substantially. We have to be careful about how the texture is applied to those triangles. If we don't pay attention the texture will seem stretched or too extended. To make it perfect we adjust the uvs for each triangle depending on their length. As you can see in the next image, when large triangles are close to small ones there can be a very significant difference between the textures.
Transparency is also important when showing skid-marks. At the beginning it has to be smooth and it has to get harder when the slide comes to its maximum, but if you suddenly stop in the middle of a slide it has to have a hard ending. To make this effect we keep in mind the velocity of the car, the angle of the slide and whether the skid-mark is starting.
As you can see skid-marks and trail-marks have a complex system. I hope you liked it and I'm willing to show more things about our game.
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