How to make a character collect items?

http://docs.unity3d.com/Documentation//ScriptReference/Collider.OnTriggerEnter.html

Save this as "SmartCollider.cs" and drag it onto your player object..

`using UnityEngine; using System.Collections;

public class SmartCollide : MonoBehaviour {

 //GameObject you might collide with 
 public Collider CollideWith;

 //if you'd like to call a function on yourself when you collide with CollideWith
 public string MessageToSelf;

 //calls a function on the collider object
 public string MessageToCollider;

 //If you want to call a function on yourself when they collide.
 public bool SendToSelf = false;

 public string OnCollisionEnterMessage, OnCollisionExitMessage, OnCollisionStayMessage,
     OnTriggerEnterMessage, OnTriggerExitMessage, OnTriggerStayMessage;

 void OnCollisionEnter(Collision collision)
 {
     if (collision.collider == CollideWith)
     {
         CollideWith.SendMessage(OnCollisionEnterMessage, SendMessageOptions.DontRequireReceiver);
         if (SendToSelf == true)
         {
             this.SendMessage(MessageToSelf, SendMessageOptions.DontRequireReceiver);
         }
     }
 }

 void OnCollisionExit(Collision collision)
 {
     if (collision.collider == CollideWith)
     {
         CollideWith.SendMessage(OnCollisionExitMessage, SendMessageOptions.DontRequireReceiver);

         if (SendToSelf == true)
         {
             this.SendMessage(MessageToSelf, SendMessageOptions.DontRequireReceiver);
         }

     }
 }

 void OnTriggerEnter(Collider collision)
 {
     if (collision.collider == CollideWith)
     {
         CollideWith.SendMessage(OnTriggerEnterMessage, SendMessageOptions.DontRequireReceiver);

         if (SendToSelf == true)
         {
             this.SendMessage(MessageToSelf, SendMessageOptions.DontRequireReceiver);
         }

     }
 }

 void OnTriggerExit(Collider collision)
 {
     if (collision.collider == CollideWith)
     {
         CollideWith.SendMessage(OnTriggerExitMessage, SendMessageOptions.DontRequireReceiver);

         if (SendToSelf == true)
         {
             this.SendMessage(MessageToSelf, SendMessageOptions.DontRequireReceiver);
         }

     }
 }

 void OnTriggerStay(Collider collision)
 {
     if (collision.collider == CollideWith)
     {
         CollideWith.SendMessage(OnTriggerStayMessage, SendMessageOptions.DontRequireReceiver);

         if (SendToSelf == true)
         {
             this.SendMessage(MessageToSelf, SendMessageOptions.DontRequireReceiver);
         }

     }
 }

}`

Now just create a function on your Gem script `public void AddGem() { OurGemsVariable += 1; }`

drag your gem object onto the Smart collide scipt where it says "CollideWith" and under the OnCollisionEnterMessage type in " AddGem "

now when your player runs into the gem it should add +1 to your gems :)

Can you help please with the same the but, I have a plane and I want to collect a gem through a spiral

thank so much................

You can do this easy!

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Collectable : MonoBehaviour
 {
 
  private void OnTriggerEnter(Collider other) 
  {
      if (other.tag == "Player")
     {
         //add points
         //add ability
         //add any powerup here
         Destroy(this.gameObject);
     }
  }
 }

make sure to add a box collider with trigger enabled

and make sure your player is tagged Player