Hi
I’m working on a Rigidbody-based first person character controller.
I’ve gotten the character to move nicely on slopes already, but there are a few cases related to exiting and entering slopes, where the movement could use some work.
I’ve also decided to not use a raycast/sphere check to detect if the player is grounded or not because I believe that way of doing ground checks is imprecise and there’s just a whole bunch of edge cases where the ground might not be detected. I’m checking the ground and its normals by looping through the contacts of the player’s collider in OnCollisionStay.
The issue is that the character is not “sticking” to the ground when a slope suddenly turns into a flat surface, the same goes for if the flat surface suddenly turns into a slope. This results in the player getting “launched” in the air. And at this point, when the player is being launched, no contacts are being registered in OnCollisionStay either.
I’ve tried to force the player to the ground by adding some force when the launch happens, though this results in sudden, non-smooth movement, and I’d rather not do it like that.
My movement code:
using UnityEngine;
public class PlayerMovement : MonoBehaviour
{
[Header("References")]
public Rigidbody rb;
public Transform orientation;
public CapsuleCollider capsuleCollider;
[Header("Movement")]
public float walkSpeed = 3.5f;
public float groundDrag = 7f;
public float jumpForce = 5f;
public float airMoveMultiplier = 0.4f;
public float maxSlopeAngle = 45f;
private Vector2 inputVector;
private bool jumpInput;
private float moveSpeed;
private bool grounded;
private GameObject currentGroundObject;
private Vector3 currentGroundNormal = Vector3.up;
private void Start()
{
moveSpeed = walkSpeed;
}
private void Update()
{
UpdateInput();
SpeedControl();
if (jumpInput && grounded)
{
Jump();
}
}
private void FixedUpdate()
{
Movement();
}
private void UpdateInput()
{
//create input vector
inputVector = new Vector2(Input.GetAxisRaw("Horizontal"), Input.GetAxisRaw("Vertical"));
inputVector.Normalize();
//jump input
jumpInput = Input.GetKeyDown(KeyCode.Space);
}
private void Movement()
{
//calculate movement direction
Vector3 moveDirection = orientation.forward * inputVector.y + orientation.right * inputVector.x;
//on slope
if (currentGroundNormal != Vector3.up)
{
rb.useGravity = false;
}
else
{
rb.useGravity = true;
}
//add force
if (grounded)
{
rb.AddForce(AdjustDirectionToSlope(moveDirection, currentGroundNormal) * moveSpeed * 10f, ForceMode.Force);
}
else
{
rb.AddForce(moveDirection * moveSpeed * 10f * airMoveMultiplier, ForceMode.Force);
}
Debug.DrawRay(transform.position, AdjustDirectionToSlope(moveDirection, currentGroundNormal), Color.red);
}
private void SpeedControl()
{
//apply drag
if (grounded)
{
rb.linearDamping = groundDrag;
}
else
{
rb.linearDamping = 0f;
}
if (currentGroundNormal != Vector3.up)
{
//limit speed on slope
if (rb.linearVelocity.magnitude > moveSpeed)
{
rb.linearVelocity = rb.linearVelocity.normalized * moveSpeed;
}
}
else
{
//limit speed on flat ground
Vector3 flatVel = new Vector3(rb.linearVelocity.x, 0f, rb.linearVelocity.z);
if (flatVel.magnitude > moveSpeed)
{
Vector3 limitedVel = flatVel.normalized * moveSpeed;
rb.linearVelocity = new Vector3(limitedVel.x, rb.linearVelocity.y, limitedVel.z);
}
}
}
private void Jump()
{
//reset y velocity then jump
rb.linearVelocity = new Vector3(rb.linearVelocity.x, 0f, rb.linearVelocity.z);
rb.AddForce(Vector3.up * jumpForce, ForceMode.Impulse);
}
private Vector3 AdjustDirectionToSlope(Vector3 direction, Vector3 normal)
{
if (grounded)
{
//prevent shifting from just using ProjectOnPlane
Vector3 movementProjectedOnPlane = Vector3.ProjectOnPlane(direction, normal);
Vector3 axisToRotateAround = Vector3.Cross(direction, Vector3.up);
float angle = Vector3.SignedAngle(direction, movementProjectedOnPlane, axisToRotateAround);
Quaternion rotation = Quaternion.AngleAxis(angle, axisToRotateAround);
return (rotation * direction).normalized;
}
return direction;
}
private bool IsFloor(Vector3 v)
{
//compare surface normal to max slope angle
float angle = Vector3.Angle(Vector3.up, v);
return angle <= maxSlopeAngle;
}
private void OnCollisionStay(Collision collision)
{
//go through contacts and check if we are on the ground
foreach (ContactPoint contact in collision.contacts)
{
//this is a valid floor
if (IsFloor(contact.normal))
{
grounded = true;
currentGroundObject = contact.otherCollider.gameObject;
currentGroundNormal = contact.normal;
return;
}
else if (currentGroundObject == contact.otherCollider.gameObject)
{
grounded = false;
currentGroundObject = null;
currentGroundNormal = Vector3.up;
}
}
}
private void OnCollisionExit(Collision collision)
{
//check if we left the ground
if (collision.gameObject == currentGroundObject)
{
grounded = false;
currentGroundObject = null;
currentGroundNormal = Vector3.up;
}
}
}
Thanks!
