Slope direction Vector3 downhill

Questions & Answers
1

I’m trying to move the player following a direction Vector, so it moves up and down the slope nicely. My approach works in the uphill direction, but not in the downhill direction. Downhill the Vector’s y component has the wrong sign and I can’t figure out a solution.

MyCode:

//getting inputs
    inputDirection = new Vector2(Input.GetAxisRaw("Horizontal"), Input.GetAxisRaw("Vertical"));
    
    //getting ground info
    RaycastHit hitInfo;
            if(Physics.SphereCast(transform.position + Vector3.up * groundCheckOffset, groundCheckRadius, -Vector3.up, out hitInfo, groundCheckDistance, groundLayer)){
                grounded = true;
                groundAngle = Vector3.SignedAngle(new Vector3(inputDirection.x, 0, inputDirection.y), hitInfo.normal, Vector3.Cross(new Vector3(inputDirection.x, 0, inputDirection.y), hitInfo.normal)) - 90f;
            }
            else{
                grounded = false;
                groundAngle = 0;
            }
    
    //calculating the velocity vector
     velocity = new Vector3(inputDirection.x, Mathf.Sin(groundAngle * Mathf.Deg2Rad), inputDirection.y).normalized * targetSpeed;

I know this probably isn’t a very good approach, but this is what I came up with.

EDIT:
added a (bad) illustration showing my problem: green sphere is the spherecast, red vector is the velocity. When going downhill it should be the dashed vector.

145920-untitled.png
145920-untitled.png1920×1080 19.7 KB

2

Hey there,

not tested but when you have your hitInfo somehting like this should be able to replace all your code:

velocity = Vector3.Cross(Vector3.Cross(hitInfo.normal, inputDirection), inputDirection).normalized * targetSpeed;

This basically gives you the slope vector in direction of inputDirection +normalization and speed and so on. Is there a reason why you are using a sherecast and not a raycast with -Vector3.up ?

Let me know if something was unclear or you need some further help on this.

EDIT: just saw your grounddetection stuff, forgot about that but i guess you’ll manage to fit that into your code.

3

To summarize:
the velocity vector is calculated with

velocity = Vector3.Cross(Vector3.Cross(hitInfo.normal, transform.TransformDirection(Vector3(inputDirection.x, 0, inputDirection.y)), hitInfo.normal).normalized * targetSpeed;

This piece of code transforms the local input vector to world space. That way if the player turns around, so does the input vector in world space.

Special Thanks to @Captain_Pineapple for his formula