Скачать или смотреть DirectX12 Car Simulator - Octree and Understeer Gradient

Here's some new stuff from my scratch built DirectX 12 car racing sim.

The focus now is on collision detection, starting with an octree for spatial partitioning which is shown here. I started with a quadtree which took a whopping 90 seconds to build for this scene, but with a little algorithmic hocus pocus I cut that down to less than 3 seconds. I switched over to an octree which runs in about the same time: A little under three seconds for this scene including all the leaves and branches in the trees. There's room to go faster still, but this is good enough for now.

The window on the left shows the octree node information at the car's position as it moves through the scene. The rendered scene geometry is used for the collision mesh instead of typical low poly collider approximations. Everything with the multithreaded engine so far has been faster than anticipated, so I'm hoping to be able to make that work with some GPU help if needed. We'll see.

Shown in the left window is the address of the current octree node, the number of triangles in it, the node size, position and extents followed by a list of triangle vertices belonging to that node. Next will be to get the tires to collide with the scene geometry with help from the octree so I can drive on something besides my silly flat test neighborhood. Currently the tire model just pretends there's an infinite flat plane at height = 0 so I haven't been able to drive on proper race tracks with this yet. Hopefully that'll change soon.

The other bigger window is understeer gradient vs lateral acceleration. I've added automated driving so the computer can do automated sweep steer tests and so on with consistency. Useful for seeing what setup changes do to the car and help dial things in to drive well. One second into the video I click the "test" button on that window which starts a sweep steer test. The computer is driving the car this time, not me. That steers to the right at a constant rate until either the front or rear tires saturate before returning control to the driver. The red and white plots are understeer gradients calculated two different ways. The red is using average front and rear tire slip angles, the white is using steering wheel angle. Throughout most of the test it's about 1.5 deg/g before terminating above that in push (limit understeer).