SphereCastTest

using UnityEngine;
using System.Collections;

public class SphereCastTest : MonoBehaviour {

    public float radiusOfSphere, distance;
    Rigidbody selectedRigidbody;
    public GameObject rayOrigin;

    public LayerMask layerMask;

    void Update () {
        Vector3 origin = rayOrigin.transform.position;
        Vector3 direction = rayOrigin.transform.forward;

        if(Input.GetButtonDown("Fire1")) {
            RaycastHit hit;
            if (Physics.SphereCast(origin, radiusOfSphere, direction, out hit, distance, layerMask))
            {
                if (hit.collider.gameObject.tag == "Pickable")
                {
                    selectedRigidbody = hit.rigidbody;
                    selectedRigidbody.constraints =
                        RigidbodyConstraints.FreezePositionZ
                        | RigidbodyConstraints.FreezeRotationX
                        | RigidbodyConstraints.FreezeRotationY
                        | RigidbodyConstraints.FreezeRotationZ;
                }
            }
        }

        if (Input.GetButtonUp("Fire1"))
        {
            if (selectedRigidbody != null)
            {
                selectedRigidbody.constraints = RigidbodyConstraints.None;
                selectedRigidbody = null;
            }
        }
    }

    void OnDrawGizmos() {
        Vector3 origin = rayOrigin.transform.position;
        Vector3 direction = rayOrigin.transform.forward;

        Color color1 = new Color(1f, 1f, 1f, 0.5f);
        Color color2 = new Color(0f, 0f, 0f, 0.5f);
        for (float t = 0, step = 0.05f; t < 1f; t += step)
        {
            Gizmos.color = Color.Lerp(color1, color2, t);
            Vector3 pos = Vector3.Lerp(origin, origin + (direction*distance), t);
            Gizmos.DrawSphere(pos, radiusOfSphere);
        }
    }
}