How to get dynamic RigidBody rotation/tilt on uneven platform?

Question

I have a rigid body with PolygonCollider2D which has some complex circular shape and I'm using uneven platform.

Im using Following code to move the object forward

CharacterRigidBody.velocity = new Vector2 (speed, CharacterRigidBody.velocity.y);

Problem : The rigid body keeps on rotating when it moves forward.

I want the character to move without rotation on asymmetrical platform(above).But i don't want to freeze rotation because i want the character to tilt when climbing or decending platform.

My RigidBody2D config(I'm using unity 5.1.2)

Can collider do anything with this problem?

Answer 1

It you look at the Rigidbody or (Rigidbody2D) in the inspector under Constraints > Freeze Rotation you will see a checkbox for each applicable axis. These checkboxes will stop the physics engine from applying any rotation about that axis.

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Now that we have stopped the physics engine from managing the rotation we can control it ourselves by manipulating either Rigidbody.rotation or Rigidbody2D.rotation.

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A Raycast can be used to do a quick search for any colliders below the player. RaycastHit.normal can then be examined to determine the slope of the collider.

Here is a sample implementation:

void FixedUpdate()
{
    // my test sprites were sometimes misaligned 
    const float standardRotation = 90f;

    // we want to ignore any colliders more distant than this
    const float rayDistance = 1f;

    // default angle
    float angle = standardRotation;

    // do we have any ground under us?
    RaycastHit2D hit = Physics2D.Raycast(transform.position, Vector2.down, rayDistance);
    if (hit)
    {
        // what is the angle of the ground?
        angle = Mathf.Atan2(hit.normal.y, hit.normal.x) * Mathf.Rad2Deg + standardRotation;
    }

    // set our rotation to this angle
    _rigidbody2d.rotation = angle;
}