Dynamic object creation in Unity3D

While creating game, we usually need to create and destroy object dynamically. Well with Unity3D its easy to create and destroy object dynamically but we need to perform few step carefully before we are able to do so.

First to be able to create a object dynamically we need to create a proper object with material applied over it.

Lets create a object which we need to create dynamically. I want to create an egg when I press some button, lets start with that.

- import image for egg sprite

- create materiel from egg sprite

- create a object with egg material applied over it

Now we have object that we need to create dynamically. But to create object dynamically we need to create a Prefab and apply object to that prefab.

 - Create a Prefab

 - Apply object to prefab

 Now we have prefab so we don't need that object any more, we can delete it so its not visible in scene anymore.

We are now ready to create object, but we need creation script. We can create a empty game object and attach creation script to it. But in this post, I am going to create a button object ( a Chicken), and when I click that button object I will create and destroy the prefab.

So let's create a script and attach it to button object.

Following is script, which create and destroy object. We need to make eggPreFab variable a Public variable so its visible outside and we can assign prefab from Unity3D interface.

using UnityEngine;
using System.Collections;

public class creation : MonoBehaviour {

 // Use this for initialization
 public GameObject eggPreFab;
 Object eggInstace = null;
 
 void Start () { 
 }
 
 // Update is called once per frame
 void Update () {  
  if( Input.anyKeyDown ){
   if( eggInstace == null )
    eggInstace = Instantiate(eggPreFab);
   else 
    Destroy(eggInstace);
  }
 }
}

Now we are almost done, but we need to assign prefab object to eggPreFab variable. To do so click button object, on script section you will see eggPreFab varible. Drop our egg prefab from asset section on this variable.

We are done, try running game. You should be able to create and destroy object now.

Beginning 2D sprite animation with Unity3D

Now that Unity is free and you can develop app for Windows phone, BB10, Android and iOS using it. I thought to give it a try.

To learn it, I started with creating simple 2D game, in which I need to switch images on object when someone touches it. It too some time to get it done first time, but finally now I know how it can be done.

So let's get started.

First we need to setup Main camera.

- I seen some videos and in one of video, author suggested to set camera at x=0,y-0, z = -10
and rotation to x=0, y=180, z=0.  I decided to use the same.

- Set camera size as 1 as its easier to deal with

- Set projection to Orthographic for 2D games.

Setup light for 2D game

We dont need to use lighting for 2D game, so we will light up whole scene by following.

Edit-> Render setting ->Ambient Light

Change Ambient light to White, It should light up whole scene

Create a cube to represent 2D object

Now we should add some object to scene.

Actually I want to render 2D image on scene, but that's not possible so we will add some 3D object and apply material over it (which is our image). And render that object to represent our image.

To do that we can add cube to scene, with proper size, Ideally we just need a plane which only one face to represent image, as that will same memory, but to learn how it works, cube will do.

Add cube to scene by Create in Hierarchy and then cube.

set position as x = 0, y = 0, z = 10

You should see a Cube in your view now.

Import image as asset

Now drag image which we need to draw to asset window,
If you want to draw animation than Image needs to be sprite sheet, I created one myself with all images i needed to be displayed.

Create material with image and apply on the Cube

We can not add image diractly to Cube, we need to create material first.
To create material,

 Project window, create ->material

Now drag image over material's texture window.

Now you can apply this material to cube, by dragging material and dropping it on cube.

Now you can see the image, but you see whole sprite sheet.  We don't want that, we need to show only one portion of sprite sheet.

Let's click material again and you will see it has tiling and offset property.

So our sprite sheet has two sprite, thus tiling will be 0.5. Let's set tiling to 0.5. Now we see proper image on cube.

If you play with offset, you can see by manipulating it we can show different sprite on cube.

By setting offset to 0.5 you can show different image on cube. We will be using this property when we add support for event, on which we will show different image.

Its showing proper image but its also showing white background, but my image is transparent. We can add transparency by selecting proper Shader.

Click material, from Shader select -> Transparent ->cutout->Diffuse

You can play with Alpha cutoff value to adjust transparency. Now it should look like below.

Handle touch event so we can animate image on touch

Now we have our 2D object, we wan to add event on it. For that we need to add script to it.

Click on object -> from Inspector window -> select Add Component -> New Script

Name it and select scripting language of your choice, I selecte c# as scripting language.

Open script, and add following code in Update method.

 void Update () {  
  if( Input.anyKey ){
   gameObject.renderer.material.mainTextureOffset = new Vector2(0.5f,0); 
  } else {
   gameObject.renderer.material.mainTextureOffset = new Vector2(0.0f,0);
  }
 }

This script will check if any key is pressed. If pressed we are setting material offset to 0.5 else 0. To display different part of sprite sheet.

OK, We are done now. Here is how it works.