Support character move forward and backward with different speed.

[watsonsong]

Support character move forward and backward with different speed. It let the backword movement can be slower.

[Sixze]

Have you tested this in multiplayer? I have doubts that it will work correctly there.

[watsonsong]

Have you tested this in multiplayer? I have doubts that it will work correctly there.

I test in PIE mode with 'Play as Listen Server' and 'Play as Client'(pure dedicated server). It seems animation and speed is correct when backward.

[Sixze]

I test in PIE mode with 'Play as Listen Server' and 'Play as Client'(pure dedicated server). It seems animation and speed is correct when backward.

But what about network simulation?

[onx2]

I'm handling this in the Input_OnMove function, as well as strafe speed. In my use case, I don't mind the sprint being a jog while moving backward, rather than the character turning into that direction at full speed.

void AAlsCharacterExample::Input_OnMove(const FInputActionValue& ActionValue)
{
    const auto Value{UAlsMath::ClampMagnitude012D(ActionValue.Get<FVector2D>())};

    const auto ForwardDirection{UAlsMath::AngleToDirectionXY(UE_REAL_TO_FLOAT(GetViewState().Rotation.Yaw))};
    const auto RightDirection{UAlsMath::PerpendicularCounterClockwiseXY(ForwardDirection)};

    float XSpeed = Value.X;
    float YSpeed = Value.Y;
    const bool bBackward = YSpeed < UE_SMALL_NUMBER;

    const bool bStrafe = FMath::IsNearlyZero(YSpeed) && !FMath::IsNearlyZero(XSpeed);

    if (bBackward)
    {
        XSpeed *= 0.5f;
        YSpeed *= 0.5f;
    }
    else if (bStrafe)
    {
        XSpeed *= 0.75f;
    }

    AddMovementInput(ForwardDirection * YSpeed + RightDirection * XSpeed);
}

[watsonsong]

I'm handling this in the Input_OnMove function, as well as strafe speed. In my use case, I don't mind the sprint being a jog while moving backward, rather than the character turning into that direction at full speed.

void AAlsCharacterExample::Input_OnMove(const FInputActionValue& ActionValue)
{
  const auto Value{UAlsMath::ClampMagnitude012D(ActionValue.Get<FVector2D>())};

  const auto ForwardDirection{UAlsMath::AngleToDirectionXY(UE_REAL_TO_FLOAT(GetViewState().Rotation.Yaw))};
  const auto RightDirection{UAlsMath::PerpendicularCounterClockwiseXY(ForwardDirection)};

  float XSpeed = Value.X;
  float YSpeed = Value.Y;
  const bool bBackward = YSpeed < UE_SMALL_NUMBER;

  const bool bStrafe = FMath::IsNearlyZero(YSpeed) && !FMath::IsNearlyZero(XSpeed);

  if (bBackward)
  {
      XSpeed *= 0.5f;
      YSpeed *= 0.5f;
  }
  else if (bStrafe)
  {
      XSpeed *= 0.75f;
  }

  AddMovementInput(ForwardDirection * YSpeed + RightDirection * XSpeed);
}

This is a good method. Simple enough and not Intrusion. But is it safe for dedicated server. Can the client may modify the backward and strafe speed, and the server can not detect it?

[onx2]

@watsonsong I'm fairly new to game development, especially networked game development, so I don't think I can speak to that with 100% certainty. However, my intuition tells me that it wouldn't be a problem because if they were able to modify this code than no matter what logic we put here there could be issues. For example, if they somehow got access to modify this code freely, even without my additions, what is stopping them from changing it to:

AddMovementInput(ForwardDirection * 99999999 + RightDirection * 9999999);

My change is just scaling down the input provided by the player so I think it should be fine in any situation. But please do your own research if you are feeling uneasy about it.

[watsonsong]

I means the only safe place is our dedicated server. And the client may be modified by any way. In the bad case, the cheater can make move backward as the speed as the forward movement.

[onx2]

I'm not sure I follow, as this is client-side code, so there is the same potential for cheating with or without a multiplier. You should always run validation on the server.

[watsonsong]

Yes that what I mean. The server does not known anything about the speed multiplier. So it possible to cheating with it. So I think It may better the limit the speed on the movement logic.