Catch-up mechanic by relaxing max speed limit a bit?

[Compl Yue]

I'm figuring out a method to implement catch-up, off the top of my head, I would give a behinder slightly higher max-speed limit, proportional to how far the other cars ahead of it.

But I'm some confused in reading the speeding code:

pixelwheels/core/src/com/agateau/pixelwheels/racer/Wheel.java

Lines 190 to 200 in 0cbca1a

 final float currentSpeed = mBody.getLinearVelocity().len() * Box2DUtils.MS_TO_KMH; 
  
 final float limit = 
         1 - 0.2f * Interpolation.sineOut.apply(currentSpeed / GamePlay.instance.maxSpeed); 
 amount *= limit; 
  
 float force = mMaxDrivingForce * amount; 
 float angle = mBody.getAngle(); 
 Vector2 pos = mBody.getWorldCenter(); 
 mBody.applyForce( 
         force * MathUtils.cos(angle), force * MathUtils.sin(angle), pos.x, pos.y, true); 

Seems there will always be some force applied to the wheel, then how it actually get max speed limited?

[Compl Yue]

pixelwheels/core/src/com/agateau/pixelwheels/racer/Vehicle.java

Lines 364 to 366 in 0cbca1a

 if (groundSpeed < 1f && !turboOn) { 
     Box2DUtils.applyDrag(mBody, (1 - groundSpeed) * GP.groundDragFactor); 
 } 

Also confused here why groundSpeed < 1f? I'd perceive 1 as a very small speed, is that the case? So the drag force only applies when it nearly stopped, so as to get it to completely still?

[Aurélien Gâteau]

Seems there will always be some force applied to the wheel, then how it actually get max speed limited?

That's a good question indeed. It's been a long time since I wrote this code, but playing with it a bit, if I remove the "0.2" factor the vehicles are very slow. I guess given a long enough straight road they would accelerate indefinitely. Or maybe there is a cap in Box2D. This game is the first time I use a physics engine, and I sometimes don't fully understand what's happening under the hood (or I dive in to understand, manage to understand, then a few weeks later I have forgotten about it...)

Also confused here why groundSpeed < 1f? I'd perceive 1 as a very small speed, is that the case?

No, groundSpeed is a "normalized" speed, where 1 means normal, no change, <1 means slow down (sand, grass, water tiles), >1 means speed up (turbo tiles). See Material.getSpeed() for the actual values. The material of a tile is defined in the .tsx files defining the tiles (in android/assets/maps). You can look at them using Tiled.

[Aurélien Gâteau]

Forgot to add: there already is a catch up mode. AI players ahead of the player are slowed down if they are better ranked, see AIPilot.updateAcceleration().

[Compl Yue]

I created #437 to experiment with the idea, shall we move the discussion to there and close this issue?

[Aurélien Gâteau]

I created #437 to experiment with the idea, shall we move the discussion to there and close this issue?

Sure.