I have been working on a game for quite long, think sonic classic physics in 3D or tony hawk psx, with unity3D. However I'm stuck at the most fundamental aspect of movement.

The requirement is that I need to move the character in mario 64 fashion (or sonic adventure) aka relative cam input:

1. the camera's forward direction always point input forward the screen, left or right input point toward left or right of the screen.

2. when input are resting, the camera direction is independent from the character direction and the camera can orbit the character

3. when input are pressed the character rotate itself until his direction align with the direction the input is pointing at.

It's super easy to do as long your movement are parallel to the global horizontal (or any world axis). However when you try to do this on arbitrary surface (think moving along complex curved surface) with the character sticking to the surface normal (basically moving on wall and ceiling freely), it seems harder. What I want is to achieve the same finesse of movement than in mario but on arbitrary angled surfaces. There is more problem (jumping and transitioning back to the real world alignment and then back on a surface while keeping momentum) but so far I didn't even take off the basics.

So far I have accomplish moving along the curved surface and the relative cam input, but for some reason direction fail all the time (point number 3, the character align slowly to the input direction).

Do you have an idea how to achieve that?

Here is the code and some demo so far:

The demo:

https://dl.dropbox.com/u/24530447/flash%20build/litesonicengine/LiteSonicEngine5.html

Camera code:

using UnityEngine;
using System.Collections;

    public class CameraDrive : MonoBehaviour
    {
        public GameObject
            targetObject;

        public Transform
            camPivot,
            camTarget,
            camRoot,

            relcamdirDebug;

        float
            rot = 0;
    //----------------------------------------------------------------------------------------------------------
        void Start()
        {
            this.transform.position = targetObject.transform.position;
            this.transform.rotation = targetObject.transform.rotation;
        }

        void FixedUpdate()
        {        
        //the pivot system
            camRoot.position    = targetObject.transform.position;

        //input on pivot orientation
            rot = 0;
            float mouse_x        = Input.GetAxisRaw( "camera_analog_X" );                //
            rot                 = rot + ( 0.1f * Time.deltaTime * mouse_x );            //
            wrapAngle( rot );                                                            //

        //when the target object rotate, it rotate too, this should not happen


            UpdateOrientation(this.transform.forward,targetObject.transform.up);

            camRoot.transform.RotateAround(camRoot.transform.up,rot);

        //debug the relcam dir
                RelativeCamDirection()
                ;

        //this camera
            this.transform.position    = camPivot.position;                            //set the camera to the pivot
            this.transform.LookAt( camTarget.position );                            //
        }
    //----------------------------------------------------------------------------------------------------------
        public float wrapAngle ( float Degree )
        {
            while (Degree < 0.0f)
            {
                Degree = Degree + 360.0f;
            }
            while (Degree >= 360.0f)
            {
                Degree = Degree - 360.0f;
            }
            return Degree;
        }

        private void UpdateOrientation( Vector3 forward_vector, Vector3 ground_normal )
        {
            Vector3
                projected_forward_to_normal_surface = forward_vector - ( Vector3.Dot( forward_vector, ground_normal ) ) * ground_normal;

            camRoot.transform.rotation = Quaternion.LookRotation( projected_forward_to_normal_surface, ground_normal );
        }

        float GetOffsetAngle( float targetAngle, float DestAngle )
        {
                return ((targetAngle - DestAngle + 180)% 360)  - 180;
        }
    //----------------------------------------------------------------------------------------------------------
        void OnDrawGizmos()
        {
            Gizmos.DrawCube(
                camPivot.transform.position,
            new Vector3(1,1,1)
                );

            Gizmos.DrawCube(
                camTarget.transform.position,
            new Vector3(1,5,1)
                );

            Gizmos.DrawCube(
                camRoot.transform.position,
            new Vector3(1,1,1)
                );
        }

        void OnGUI()
        {
            GUI.Label(new Rect(0,80,1000,20*10), "targetObject.transform.up : " + targetObject.transform.up.ToString());
            GUI.Label(new Rect(0,100,1000,20*10), "target euler : " + targetObject.transform.eulerAngles.y.ToString());
            GUI.Label(new Rect(0,100,1000,20*10), "rot : " + rot.ToString());

        }
    //----------------------------------------------------------------------------------------------------------
        void RelativeCamDirection()
        {

            float
                input_vertical_movement     = Input.GetAxisRaw( "Vertical" ),
                input_horizontal_movement     = Input.GetAxisRaw( "Horizontal" );

            Vector3
                relative_forward     = Vector3.forward,
                relative_right         = Vector3.right,

                relative_direction    =
                    ( relative_forward    * input_vertical_movement )
                    +
                    ( relative_right    * input_horizontal_movement )
                    ;

            MovementController MC = targetObject.GetComponent<MovementController>();

            MC.motion = relative_direction.normalized * MC.acceleration * Time.fixedDeltaTime;

            MC.motion = this.transform.TransformDirection( MC.motion );

            //MC.transform.Rotate(Vector3.up, input_horizontal_movement * 10f * Time.fixedDeltaTime);    
        }
    }

Mouvement code:

using UnityEngine;
using System.Collections;

public class MovementController : MonoBehaviour
{
    public float
        deadZoneValue = 0.1f,
        angle,
        acceleration  = 50.0f;
    public Vector3
        motion ;

//--------------------------------------------------------------------------------------------    
    void OnGUI()
    {
        GUILayout.Label( "transform.rotation : " + transform.rotation );
        GUILayout.Label( "transform.position : " + transform.position );
        GUILayout.Label( "angle : " + angle );
    }

    void FixedUpdate ()
    {

        Ray
            ground_check_ray = new Ray( gameObject.transform.position, -gameObject.transform.up );
        RaycastHit
            raycast_result;
        Rigidbody
            rigid_body = gameObject.rigidbody;

        if ( Physics.Raycast( ground_check_ray, out raycast_result ) )
        {
            Vector3
                next_position;

            //UpdateOrientation( gameObject.transform.forward, raycast_result.normal );
            UpdateOrientation( gameObject.transform.forward, raycast_result.normal );    
            next_position = GetNextPosition( raycast_result.point );
            rigid_body.MovePosition( next_position );
        }
    }
//--------------------------------------------------------------------------------------------    


    private void UpdateOrientation( Vector3 forward_vector, Vector3 ground_normal )
    {
        Vector3
            projected_forward_to_normal_surface = forward_vector - ( Vector3.Dot( forward_vector, ground_normal ) ) * ground_normal;

        transform.rotation = Quaternion.LookRotation( projected_forward_to_normal_surface, ground_normal );
    }

    private Vector3 GetNextPosition( Vector3 current_ground_position )
    {
        Vector3
            next_position;

//        //--------------------------------------------------------------------
//        angle = 0;
//        Vector3 dir = this.transform.InverseTransformDirection(motion);
//        angle = Vector3.Angle(Vector3.forward, dir);// * 1f * Time.fixedDeltaTime;
//        
//        if(angle > 0) this.transform.Rotate(0,angle,0);
//        //--------------------------------------------------------------------


        next_position =
            current_ground_position +
            gameObject.transform.up * 0.5f
                + motion
                ;

        return next_position;
    }

}

Some observation:

I have the correct input, I have the correct translation in the camera direction ... but whenever I attempt to slowly lerp the direction of the character in direction of the input, all I get is wild spin! Sad

Also discovered that strafing to the right (immediately at the beginning without moving forward) has major singularity trapping on the equator!!

I'm totally lost and crush (I have already done a much more featured version which fail at the same aspect)