====== Change the color of a ball when it enters and exits a box ======

> This article was written for "UniVCI-0.15."
=== Example data ===
https://virtualcast.jp/products/3f4a199e2408e4447ac65547a040f882f5ed085ec4ec1eb1416ed519aa2cf43e


To execute a process when a Collider (Trigger) collides with a SubItem, use "**onTriggerEnter**".\\
To execute a process when a Collider (Trigger) disengages, use "**onTriggerExit**".

1. Create a new GameObject and create a Cube, a Sphere and a Plane as its child.\\
\\
In this example, we named the GameObject "TriggerEnterExit_VCI," but it can be anything really.\\
Configure the objects as below:

    * Cube (box): Set the Y-coordinate of the **Cube** 1.0
    * Sphere (ball): Set the Y-coordinate of the **Ball** 2.0
    * Plane (ground): Set the Y-coordinate of the **Plane** 0.0

2. To change the color of the Cube, create a new material file "**TriggerMaterial**".
Set the created TriggerMaterial as the material of the **Cube**.

3. Attach a "**VCI Object**" component on the GameObject,\\
and attach the "**VCI SubItem**" component on the Cube, Ball and Plane.\\
When doing this, "RigidBody" components are also attached automatically.\\
As the Cube and the Plane won't be using gravity, turn off **Use Gravity** and turn on **Is Kinematic**.\\
As we need the Ball to have physics, turn on **Use Gravity** and turn off **Is Kinematic**.

4. On the VCI Object component in the GameObject, set the Scripts Size as **1**.\\
Enter "main.lua" in the Name and paste the script shown below.

<file lua main.lua>
local green = Color.__new(0,1,0,0.5)
local red = Color.__new(1,0,0,0.5)

function onTriggerEnter(item, hit)
    if item == "Ball" and hit == "Cube" then
        vci.assets._ALL_SetMaterialColorFromName("TriggerMaterial", red)
    end
end
function onTriggerExit(item, hit)
    if item == "Ball" and hit == "Cube" then
        vci.assets._ALL_SetMaterialColorFromName("TriggerMaterial", green)
    end
end
</file>