Framerate-independent idPlayer::Move() and idAI::AdjustFlyingAngles()

thanks to Github user tyuah8:
dhewm#584 (comment)

neo/d3xp/Player.cpp

@@ -7117,8 +7117,12 @@ void idPlayer::Move( void ) {
  if ( spectating ) {
  SetEyeHeight( newEyeOffset );
  } else {
+ // DG: make this framerate-independent, code suggested by tyuah8 on Github
+ // https://en.wikipedia.org/wiki/Exponential_smoothing#Time_constant
+ const float tau = -16.0f / idMath::Log( pm_crouchrate.GetFloat() );
+ const float a = 1.0f - idMath::Exp( -gameLocal.gameMsec / tau );
  // smooth out duck height changes
- SetEyeHeight( EyeHeight() * pm_crouchrate.GetFloat() + newEyeOffset * ( 1.0f - pm_crouchrate.GetFloat() ) );
+ SetEyeHeight( EyeHeight() * (1.0f - a) + newEyeOffset * a );
  }
  }
 

neo/d3xp/ai/AI.cpp

@@ -2984,8 +2984,15 @@ void idAI::AdjustFlyingAngles( void ) {
  }
  }
 
- fly_roll = fly_roll * 0.95f + roll * 0.05f;
- fly_pitch = fly_pitch * 0.95f + pitch * 0.05f;
+ // DG: make this framerate-independent, code suggested by tyuah8 on Github
+ // https://en.wikipedia.org/wiki/Exponential_smoothing#Time_constant
+ static const float tau = -16.0f / idMath::Log( 0.95f );
+ // TODO: use gameLocal.gameMsec instead, so it's not affected by slow motion?
+ // enemies turning slower in slowmo seems logical, but the original code
+ // just increased every tic and thus was independent of slowmo
+ const float a = 1.0f - idMath::Exp( -gameLocal.msec / tau );
+ fly_roll = fly_roll * (1.0f - a) + roll * a;
+ fly_pitch = fly_pitch * (1.0f - a) + pitch * a;
 
  if ( flyTiltJoint != INVALID_JOINT ) {
  animator.SetJointAxis( flyTiltJoint, JOINTMOD_WORLD, idAngles( fly_pitch, 0.0f, fly_roll ).ToMat3() );

neo/game/Player.cpp

@@ -6014,8 +6014,12 @@ void idPlayer::Move( void ) {
  if ( spectating ) {
  SetEyeHeight( newEyeOffset );
  } else {
+ // DG: make this framerate-independent, code suggested by tyuah8 on Github
+ // https://en.wikipedia.org/wiki/Exponential_smoothing#Time_constant
+ const float tau = -16.0f / idMath::Log( pm_crouchrate.GetFloat() );
+ const float a = 1.0f - idMath::Exp( -gameLocal.gameMsec / tau );
  // smooth out duck height changes
- SetEyeHeight( EyeHeight() * pm_crouchrate.GetFloat() + newEyeOffset * ( 1.0f - pm_crouchrate.GetFloat() ) );
+ SetEyeHeight( EyeHeight() * (1.0f - a) + newEyeOffset * a );
  }
  }
 

neo/game/ai/AI.cpp

@@ -2896,8 +2896,12 @@ void idAI::AdjustFlyingAngles( void ) {
  }
  }
 
- fly_roll = fly_roll * 0.95f + roll * 0.05f;
- fly_pitch = fly_pitch * 0.95f + pitch * 0.05f;
+ // DG: make this framerate-independent, code suggested by tyuah8 on Github
+ // https://en.wikipedia.org/wiki/Exponential_smoothing#Time_constant
+ static const float tau = -16.0f / idMath::Log( 0.95f );
+ const float a = 1.0f - idMath::Exp( -gameLocal.msec / tau );
+ fly_roll = fly_roll * (1.0f - a) + roll * a;
+ fly_pitch = fly_pitch * (1.0f - a) + pitch * a;
 
  if ( flyTiltJoint != INVALID_JOINT ) {
  animator.SetJointAxis( flyTiltJoint, JOINTMOD_WORLD, idAngles( fly_pitch, 0.0f, fly_roll ).ToMat3() );