Handling Contacts on Collision

using System;
using System.Collections;
using System.Collections.Generic;
using Unigine;
 
    // DO NOT CHANGE THE PropertyGuid VALUE
[Component (PropertyGuid = "YOUR_GUID")]

public class ContactsHandler : Component
{   
    // For debugging
    public bool debug = true; 
	// A node that will be loaded on contact (a hit effect in our case)
    public AssetLinkNode contactEffect; 
 
    // Time, position and some info of the last occurred contact
    private DateTime lastContactTime; 
    private vec3 lastContactPoint;
    private string lastContactInfo;
        
    private void Init()
    {         
        Body body = node.ObjectBody;
        if (body)
        {   
			// For debug purposes, we can render certain contacts depending on their type    
            body.AddContactsCallback((b) => b.RenderInternalContacts()); 
			// A callback to be fired when each contact emerges
            body.AddContactEnterCallback(OnContactEnter);                        
        }   
    }
    
	// This function takes the body and the index of the contact
    private void OnContactEnter(Body body, int num) 
    {
		// Enable Visualizer to see the rendered contact points
		Visualizer.Enabled = true;
		
        if(body.IsContactInternal(num))
        {
            if (debug)
            {	
				// The time of the contact
                lastContactTime = DateTime.Now; 
                // The position of the contact
				lastContactPoint = body.GetContactPoint(num); 
                
				// We get both physical bodies participating in this contact
                Body body0 = body.GetContactBody0(num);
                Body body1 = body.GetContactBody1(num);
 
                Body touchedBody = null;
 
				// We check if our object has hit another physical object.
				// If any of the bodies exists and it's not the body of our object
				// then we have found another physics-driven object that hit it
                if (body0 && body0 != body) touchedBody = body0;  
                if (body1 && body1 != body) touchedBody = body1;
                
                if (touchedBody)
                {
					// Our object has touched a physics-driven object.
					// We save the info about the body
                    lastContactInfo = $"body {touchedBody.Name} of {touchedBody.Object.Name}";
					// Render it in the viewport
                    Visualizer.RenderObject(touchedBody.Object, vec4.BLUE, 0.5f); 
                }
                 else
                 {
                     // It has touched a surface with Collision enabled
                     lastContactInfo = $"surface #{body.GetContactSurface(num)} of {body.GetContactObject(num).Name}";
					 // Highlighting the surface
                     Visualizer.RenderObjectSurface(body.GetContactObject(num), body.GetContactSurface(num), vec4.BLUE, 0.5f); 
                 }
                 
                 // You can add details you are interested in (e.g., the contact impulse)
                 lastContactInfo += $"\nimpulse: {body.GetContactImpulse(num):0.0}";
            }
            
			// We spawn a hit effect if the impulse is strong enough
            if (body.GetContactImpulse(num) > 0.3f && !contactEffect.IsNull) 
            {
                contactEffect.Load(body.GetContactPoint(num), MathLib.RotationFromDir(body.GetContactNormal(num) * MathLib.RotateY(90)));
            }
        }
    }
 
    private void Update()
    {
        // Here we display the info and create a slow motion effect for one second
    
        if (debug)
        {
            if((DateTime.Now - lastContactTime).Seconds < 1.0f)
            {
                // Slow motion effect
				Game.Scale = 0.4f; 
                Visualizer.RenderMessage3D(lastContactPoint, vec3.ONE, $"last contact: \n{lastContactInfo}", vec4.GREEN, 2, 24);
            }
            
				
            else
            {	
				// All the other time the speed will be normal
                Game.Scale = 1.0f;
            }           
        }
    }
}