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VehicleMovement Drag Force wrong direction

VehicleMovementComponent -> Drag Force Parameter

The drag force should simulate air drag force and slow the car down at high speeds

Bug: The Drag force is not applied on a local vector of the car [-X], but on a world axis [-X]. This leads to drifting while driving parallel to the world [Y] axis, or crazy accelleration while driving in world[-X] direction.

Notice: This effect can only be seen with fast moving cars, or cars of extreme low mass. I myself needed 3hours to figure out why my car was drifting always in world[-X] while driving on ice (low tire fraction)

How to repruduce:

  1. Create a WheeledVehicle BP

  2. Import a car, set everything up (the car from the content packs will work too, if they use a vehiclemovementcomponent)

  3. Change the mass inside the VehicleMovementComponent to a low value like 10kg. This will make sure, you can see the effect. You might also set the tire friction a little lower like 0.4

  4. Make sure VehicleMovementComponent->"Drag Force" <>0 (higher values work better)

  5. Auto Posses Player 0 in game, drag car into a level.

  6. Play the game. Align car to World Y-Axis and speed up. The faster the car goes, the more it will be dragged to World [-X] Axis.

  7. If you can't reproduce, build a little ramp aligned World Y-Axis. The Tire Friction may cause the issue. If no tires are on the ground or the front wheels lift a little when going full throttle, the effect will be seen much better.

best regards, Tank

Product Version: UE 4.18
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asked Feb 12 '18 at 03:19 AM in Bug Reports

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TankbusterGames
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avatar image Sean L ♦♦ STAFF Feb 12 '18 at 12:36 PM

Hello,

We've recently made a switch to a new bug reporting method using a more structured form. Please visit the link below for more details and report the issue using the new Bug Submission Form. Feel free to continue to use this thread for community discussion around the issue.

https://forums.unrealengine.com/unreal-engine/announcements-and-releases/1410408-unreal-engine-bug-submission-form

Thanks

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Sorry, the value is called "Drag Coefficent" and not "Drag Force". You can find it:

VehicleMovementComponent->VehicleSetup->Drag Coefficent

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answered Feb 12 '18 at 03:22 AM

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TankbusterGames
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