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TIGSource ForumsDeveloperTechnical (Moderator: ThemsAllTook)Box2d car accelerator doing wrong , car doesn't accelerate Right
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Author Topic: Box2d car accelerator doing wrong , car doesn't accelerate Right  (Read 913 times)
umen
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« on: May 06, 2015, 05:20:38 AM »
i have simple car using box2d ( currently done in c++ but it really doesn't matter ).
any way when i try to make the car accelerate when right key is pressed
the car moves very slowly and doesn't accelerate

this is the function called from the main loop

Code:
 MonsterTruck::upArrowPressed (float dt)
    {
      float acceleration = 4000.0f;
      
      speed = acceleration ;
      
      frontMotor->SetMotorSpeed(speed *-1);
      frontMotor->SetMaxMotorTorque(12);
      rearMotor->SetMotorSpeed(speed*-1);
      rearMotor->SetMaxMotorTorque(14);
      // truckBody->ApplyTorque(280.0,true);
    }


the speed value do rise up :
here is the printing using the car body from and rear wheels  GetLinearVelocity()

Code:
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.045660 frontWheel x:-0.029360 rearWheel x:0.111595
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.045660 frontWheel x:-0.029360 rearWheel x:0.111595
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:-0.521213 frontWheel x:0.177735 rearWheel x:0.402440
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:-0.521213 frontWheel x:0.177735 rearWheel x:0.402440
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:-0.098060 frontWheel x:0.097710 rearWheel x:0.545645
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:-0.098060 frontWheel x:0.097710 rearWheel x:0.545645
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.427969 frontWheel x:0.047905 rearWheel x:0.645439
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.427969 frontWheel x:0.047905 rearWheel x:0.645439
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.683802 frontWheel x:0.090198 rearWheel x:0.745614
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.683802 frontWheel x:0.090198 rearWheel x:0.745614
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.736764 frontWheel x:0.231306 rearWheel x:0.840791
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.736764 frontWheel x:0.231306 rearWheel x:0.840791
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.757946 frontWheel x:0.435451 rearWheel x:0.914402
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.757946 frontWheel x:0.435451 rearWheel x:0.914402
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.832796 frontWheel x:0.647440 rearWheel x:0.963335
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.832796 frontWheel x:0.647440 rearWheel x:0.963335
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.952683 frontWheel x:0.857393 rearWheel x:0.996945
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:0.952683 frontWheel x:0.857393 rearWheel x:0.996945
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.083822 frontWheel x:1.063201 rearWheel x:1.028042
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.083822 frontWheel x:1.063201 rearWheel x:1.028042
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.206601 frontWheel x:1.259915 rearWheel x:1.066999
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.206601 frontWheel x:1.259915 rearWheel x:1.066999
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.319148 frontWheel x:1.439424 rearWheel x:1.120500
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.319148 frontWheel x:1.439424 rearWheel x:1.120500
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.426374 frontWheel x:1.594379 rearWheel x:1.192358
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.426374 frontWheel x:1.594379 rearWheel x:1.192358
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.531648 frontWheel x:1.721108 rearWheel x:1.284282
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.531648 frontWheel x:1.721108 rearWheel x:1.284282
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.635143 frontWheel x:1.820028 rearWheel x:1.396084
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.635143 frontWheel x:1.820028 rearWheel x:1.396084
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.736019 frontWheel x:1.895020 rearWheel x:1.525629
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.736019 frontWheel x:1.895020 rearWheel x:1.525629
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.833965 frontWheel x:1.951651 rearWheel x:1.669067
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.833965 frontWheel x:1.951651 rearWheel x:1.669067
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.929649 frontWheel x:1.996796 rearWheel x:1.821317
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:1.929649 frontWheel x:1.996796 rearWheel x:1.821317
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.024153 frontWheel x:2.037911 rearWheel x:1.976777
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.024153 frontWheel x:2.037911 rearWheel x:1.976777
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.118779 frontWheel x:2.081938 rearWheel x:2.129954
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.118779 frontWheel x:2.081938 rearWheel x:2.129954
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.214476 frontWheel x:2.134749 rearWheel x:2.276090
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.214476 frontWheel x:2.134749 rearWheel x:2.276090
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.311927 frontWheel x:2.200994 rearWheel x:2.411549
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.311927 frontWheel x:2.200994 rearWheel x:2.411549
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.411601 frontWheel x:2.283393 rearWheel x:2.534090
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.411601 frontWheel x:2.283393 rearWheel x:2.534090
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.513546 frontWheel x:2.382733 rearWheel x:2.643006
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.513546 frontWheel x:2.382733 rearWheel x:2.643006
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.617588 frontWheel x:2.497957 rearWheel x:2.739017
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.617588 frontWheel x:2.497957 rearWheel x:2.739017
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.723354 frontWheel x:2.626366 rearWheel x:2.824085
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.723354 frontWheel x:2.626366 rearWheel x:2.824085
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.830351 frontWheel x:2.764125 rearWheel x:2.901086
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.830351 frontWheel x:2.764125 rearWheel x:2.901086
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.937965 frontWheel x:2.906741 rearWheel x:2.973433
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:2.937965 frontWheel x:2.906741 rearWheel x:2.973433
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:3.045582 frontWheel x:3.049551 rearWheel x:3.044664
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:3.045582 frontWheel x:3.049551 rearWheel x:3.044664
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:3.152529 frontWheel x:3.188292 rearWheel x:3.118098
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:3.152529 frontWheel x:3.188292 rearWheel x:3.118098
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:3.258285 frontWheel x:3.319448 rearWheel x:3.196472
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:3.258285 frontWheel x:3.319448 rearWheel x:3.196472
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:3.362544 frontWheel x:3.440575 rearWheel x:3.281735
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:3.362544 frontWheel x:3.440575 rearWheel x:3.281735
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:3.465011 frontWheel x:3.550358 rearWheel x:3.374908
MonsterTruck::upArrowPressed : speed:-4000.000000
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:3.465011 frontWheel x:3.550358 rearWheel x:3.374908
MonsterTruck::upArrowPressed : Befor acceleration truckBody->GetLinearVelocity() x:3.565691 frontWheel x:3.649129 rearWheel x:3.476057



but the car move slowly
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mokesmoe
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« Reply #1 on: May 12, 2015, 01:28:55 AM »
You are setting your speed to your acceleration when you need to be adding your acceleration to your speed (speed += acceleration)

You will also need to initialize your speed to 0 when creating the truck, and you will want to simulate friction by lowering the speed back towards 0 when not pressing the key.
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