Movement issue, the player accelerates but does not reduce in speed when hitting a wall or object

Hi there,

I'm working on some first person movement code which is based on the Quake 3 source code, which was ported by 'Zinglish' here: https://github.com/Zinglish/quake3-movement-unity3d/blob/master/CPMPlayer.cs

The issue I'm having with my script, is that the player accelerates whilst in the air but if the player hits a wall or object and slows down even so they are not moving except jumping, the previous speed they were travelling before hitting the object is retained, which is unwanted. I want the player to slow down when hitting objects.

Here is the relevant code: void Update() { / Movement / QueueJump(); if (characterController.isGrounded) GroundMove();

         if (!characterController.isGrounded)
             AirMove();
 
         // Move the player
         characterController.Move(playerVelocity * Time.deltaTime);
     }
 
 /* Sets the direction based on player input */
     private void SetMovementDirection()                                                         
     {
         commands.forwardMove = Input.GetAxisRaw("Vertical");
         commands.sideMove = Input.GetAxisRaw("Horizontal");
     }
 
     /* If the jump key is pressed while in the air, the player will jump instantly when they hit the ground */
     private void QueueJump()                                                                    
     {
         if (Input.GetButton("Jump") && !queueJump)
             queueJump = true;
 
         if (Input.GetButtonUp("Jump"))
             queueJump = false;
     }
 
     /* Returns the scale factor to apply to the movement direction */
     private float MovementScale()
     {
         int Maximum;
         float Total;
         float Scale;
 
         Maximum = (int)Mathf.Abs(commands.forwardMove);
         if (Mathf.Abs(commands.sideMove) > Maximum)
             Maximum = (int)Mathf.Abs(commands.sideMove);
         if (Maximum <= 0)
             return 0;
 
         Total = Mathf.Sqrt(commands.forwardMove * commands.forwardMove + commands.sideMove * commands.sideMove);
         Scale = movementSpeed * Maximum / (moveScale * Total);
 
         return Scale;
     }
 
     private void Accelerate(Vector3 Direction, float Speed, float Acceleration)
     {
         float AddSpeed;
         float AccelerationSpeed;
         float CurrentSpeed;
 
         // Stop the player exceeding the speed cap
         if (Speed >= playerVelocityCap)
             return;
 
         CurrentSpeed = Vector3.Dot(playerVelocity, Direction);
         AddSpeed = Speed - CurrentSpeed;
         if (AddSpeed <= 0)
             return;
 
         AccelerationSpeed = Acceleration * Time.deltaTime * Speed;
         if (AccelerationSpeed > AddSpeed)
             AccelerationSpeed = AddSpeed;
 
         playerVelocity.x += AccelerationSpeed * Direction.x;
         playerVelocity.z += AccelerationSpeed * Direction.z;
     }
 
 // This function is called when the player is the on the ground
     private void GroundMove()                                                                   
     {
         Vector3 Direction;
 
         // If a jump is queued, don't apply friction 
         if (!queueJump)                                                                        
             ApplyFriction(1f);
         else
             ApplyFriction(0);
 
         Direction = new Vector3(commands.sideMove, 0, commands.forwardMove);
         Direction = transform.TransformDirection(Direction);
         moveDirectionNorm = Direction;
 
         var Speed = Direction.magnitude;
         Speed *= movementSpeed;
 
         Accelerate(Direction, Speed, runAcceleration);
 
         // Reset gravity velocity
         playerVelocity.y = 0;                                                                  
 
         if (queueJump)
         {
             playerVelocity.y = jumpSpeed;
             PlayJumpSound();
             queueJump = false;
             landSoundPlayed = false;
         }
     }
 
     private void AirMove()
     {
         Vector3 Direction;
         float Acceleration;
         float Scale = MovementScale();
 
         SetMovementDirection();
 
         // Multiplier applied to the sidemove command to serverly reduce strafing while in the air
         Direction = new Vector3(commands.sideMove * airStrafeSpeed, 0, commands.forwardMove);            
         Direction = transform.TransformDirection(Direction);
 
         float Speed = Direction.magnitude;
         Speed *= movementSpeed;
 
         Direction.Normalize();
         moveDirectionNorm = Direction;
         Speed *= Scale;
 
         /* Air control */
         float AirSpeed = Speed;
         if (Vector3.Dot(playerVelocity, Direction) < 0f)
             Acceleration = airDecceleration;
         else
             Acceleration = airAcceleration;
 
         // If the player is ONLY strafing left or right
         if (commands.forwardMove == 0 && commands.sideMove != 0)                              
         {
             if (Speed > airStrafeSpeedGen)
                 Speed = airStrafeSpeedGen;
             Acceleration = airStrafeAcceleration;
         }
 
         Accelerate(Direction, Speed, Acceleration);
 
         if (airControlPresicion > 0)
             AirControl(Direction, AirSpeed);
 
         // Apply gravity
         playerVelocity.y -= gravity * Time.deltaTime;
 
         // If the player jumps or they are falling, the landing sound will play when they hit the ground
         if (playerVelocity.y > 1 || playerVelocity.y < -1)
             landSoundPlayed = false;
     }
 
     private void AirControl(Vector3 Direction, float AirSpeed)
     {
         float ZSpeed;
         float Speed;
         float Dot;
         float K;
 
         // Air control only works when moving forward or backwards
         if (Mathf.Abs(commands.forwardMove) < 0.001 || Mathf.Abs(AirSpeed) < 0.001)            
             return;
 
         // Air control stops working if a strafe key is pressed
         if (Mathf.Abs(commands.sideMove) > 0)
             return;
 
         ZSpeed = playerVelocity.y;
         playerVelocity.y = 0;
         Speed = playerVelocity.magnitude;
 
         playerVelocity.Normalize();
 
         Dot = Vector3.Dot(playerVelocity, Direction);
         K = 32;
         K *= airControlPresicion * Dot * Dot * Time.deltaTime;
 
         // Change direction while slowing down
         if (Dot > 0)                                                                            
         {
             playerVelocity.x = playerVelocity.x * Speed + Direction.x * K;
             playerVelocity.y = playerVelocity.y * Speed + Direction.y * K;
             playerVelocity.z = playerVelocity.z * Speed + Direction.z * K;
 
             playerVelocity.Normalize();
             moveDirectionNorm = playerVelocity;
         }
 
         playerVelocity.x *= Speed;
         playerVelocity.y = ZSpeed;
         playerVelocity.z *= Speed;
     }

There must be some issue in the code which is making the player retain their speed even after slowing down, but I have tried for days to fix this issue with no results, I'm quite desperate now! Please help. Thanks in advance!