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VIRTUAL RC RACING – THE INSIDE STORY Episode 18

13.05.2022   Category: Site news

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Episode 18: First steps into offroad – Short Course Trucks

After we had finished the electric on-road classes our focus changed to off-road. A new challenge for us because we were now entering an discipline where we had zero experience. I am disregarding the few years back in in the early 80-ties when we had a short off-road adventure with the Serpent Cobra and Spirit. There was zero data, zero experience, so where to start? And what chassis class to take on first?

What I did know was that we had to develop physics for off-road from scratch, model new cars and create new tracks. And I had no idea how close we could get to a real ‘off-road’ feel with such a new chassis, and would the undulated off-road tracks be of the same high standard as we had reached with on-road? In other words, could we make that giant leap to cross the ‘uncanny’ off-road valley so off-road racers would embrace this new effort as a true and realistic off-road class? Al lot of uncertainties. Speaking to Todd (physics) and Tony (graphics) gave me the confidence that we could pull this off although it was going to be a big challenge. And it was going to take time. One thing I knew already, the new VRC Pro game architecture and database was capable of including such new classes, no major work to be done on that end.

Associated SC10 short course truck
One of the most popular cars back in 2010 was the electric short course truck. It was immensely popular in the US, especially because full-size Short Course Truck races were on TV every week, the racing was exciting, and some RC car manufacturers had even become involved with sponsoring this new racing hype, like Traxxas and Associated. I had already established good contacts with Associated, they had been distributing our VRC-3 USB adapter in the US, and as they were the market leader in the SC truck it was an obvious choice for us to join forces. We would model their SC10 truck, and they would provide us with all the required chassis data, especially chassis and driveline inertia which they could retrieve from their 3D design and engineering software Solid Works. Big thanks to Cliff Lett!

From 2D to 3D suspension model
Up till then the physics model of all the on-road chassis we had done, except for the 1:12 chassis, used a 2D suspension geometry model. The suspension movements of the on-road chassis are very small and therefore a 2D model would suffice, and the suspension itself was also not visible, just the wheels. Todd’s 2D suspension model was able to calculate the chassis roll, jaw and pitch, and the camber and caster angle changes. On a side note, the 1:12 suspension model was half 2D and half 3D because of the swiveling rear end.

3DS – the new 3D Suspension model
We had already planned for buggies if the SC Truck was successful, and with the suspension and shocks being fully exposed outside the body we knew that we would need a new 3D suspension model, for the arms and steering links, and for the shock absorbers and springs. The 3D suspension model was not only needed for the physics calculations but also to animate the suspension arms, steering blocks, steering tie-rods, shocks and springs. For all this to work in the game Todd had to coordinate and adjust this with Tony who had to model the chassis and the suspension components so everything would fit and could be animated in real time!

I think Todd has worked on this new suspension model for over a year and the result was truly amazing, and eye-dropping impressive when I saw it for the first time. Todd had sent me a video of the animated suspension in which he showed all the adjustments that could be made in the new 3DSuspension model. I added some slow-motion footage of the chassis without the body so you could see all the suspension components and chassis roll, pitch and yaw in full action while driving the car. And all this had to work at very high frame rates. Todd had to reduce the rate of the physics calculations from 500 to 350 Hz in order to cope with the extra calculations that had to be carried out for 3DS. But still 350 calculations per second! And a new challenge for Miro’s graphics engine to enable the rendering of the 3D suspension movements with the highest possible frame rate. In episode 16 I already explained how we used LOD, Level Of Detail optimization to enable the graphics engine to render a full field of 10 off-road cars at frame rates well over 200 fps (frames per second).

I have posted that animation video with this publication, to illustrate what we have been able to achieve with the new 3DS physics. Up until today it impresses me every time I watch it. It was the basis of all the other off-road cars to follow, although Todd expanded on it even further for the buggies. I’ll create another video of the buggy suspension which is used for the nitro and electric buggy, and Rally-X chassis which I will write about in a later episode.

Off-road tires
We were faced with a whole new breed of tires, profiled rubber tires. We had tire testing data from the rubber tires used in electric on-road which gave us a good indication about the effects of tire deflection under load and how this would affect lateral and longitudinal traction and grip in the physics model. The different profiles would most probably have a more straight forward linear effect on the lateral and longitudinal traction and therefore we decided not to go into a new series of tire tests. Todd was quite sure that we could probably do the fine tuning of the tires to get the right ‘feel’ in beta testing. That’s exactly what we did. Todd provided a series of off-road tires for beta testing and based on the feedback he received, he adjusted parameters to bring the tire closer to a real off-road feel.

Another important factor in the off-road ‘feel’ was of course the track surface with variable grip levels depending on how much dust there was on different parts of the tracks. This part was shifted to Tony, we already had a solution for this for on-road tracks and that could be used for off-road too. All in all, the tires were quite a challenge, but we relied on our experience with electric on-road to get them right. And we did!

Off-road tracks
Going from flat tarmac on-road tracks to rough terrain dirt off-road tracks presented a number of new challenges to Todd and Tony. First of all we needed much more detailed reference material for Tony to model the tracks as accurately as possible. The sequence of the jumps and the take-off and landing angles were as critical for the acceptance of our off-road success as the behavior of the chassis.

The very first off-road track we did was the Rhein-Main track in Germany. Todd and I visited the LRP Master in Eppelheim and we found out that the Rhein Main track wasn’t that far away from Eppelheim. So, we decided to go there, take a look and gather reference material. I took all the pictures and did all the measurements! It was the very first time for both Todd and I to see a large-size off-road track and more importantly, watch the off-road cars race on that track. It surely was an eyeopener for Todd which provided very valuable input to him for the further development of off-road physics.

Rhein Main was used as the beta test track, it had everything we needed to fine tune the chassis, the tires and the track itself. We added a few more indoor off-road tracks as short course trucks were also raced a lot indoors. I contacted the owner of the Mikes Hobby Shop track in Carrolton Texas, a very popular indoor sc truck facility. They frequently changed the lay-out of the track, so we ended up with 3 versions of that track. Owner Mike provided us with very precise reference material. That track facility is gone for several years now, but the tracks lives on in VRC!

Another off-road essential: dust
What would off-road be without dust? OK, some off-road tracks have very hard surfaces and hardly produce any dust, but most do. Therefore, Todd had to develop this, again starting from scratch! First question was: what is dust? Dust consists of very small particles which are shot off in the air and then drop back on earth. These dust particles are subject to speed, direction, gravity, and aerodynamics. Todd therefore had to develop a particle system which would provide information to the graphics engine about how much dust particles (density), the speed of these particles (velocity) and the direction of these particles and how they spread and disperse. In fact, very similar to what Todd had already developed to simulate smoke coming from an exhaust pipe! But this was even more complex and very important, should not kill framerate! Off-road was already making a much bigger demand on CPU and GPU resources than on-road. This new challenge was once again met by Todd! Another key element to the success of our off-road adventure added!

It took well over 2 years to develop the new 1:10 electric Short Course Truck class and a series of off-road track, our first (and successful it turned out) effort into off-road. This class was released in 2012, shortly after VRC Pro was released end of 2011. But there were several more novelties in VRC Pro. Like the interactive pit table and the in-game commercials.

That’s next.

Comments

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(Total posts: 1)
19.05.2022 [08:26]
It would be nice to see some, 2wd and 4wd 1/10 scale rc cars!

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