Is there any way to make some rectangular areas of a mask to be transparent? - unity3d

Question

I am using UGUI to make a Novice guide to guide people to play my game.
And need the whole UI be mask, but some rectangular areas to be lighted.
How to do?

Answer 1

Create a new gameobject and add a image component to it. Create a image with transparent areas where you want your ui to be visible. Assign that image to the image component. Then add a mask component
Put your other gui elements inside this gameobject so that is could overlap and hide everything except transparent areas. Here is the picture of demo setup.

Answer 2

IMHO, what you want to achieve is not easy to be done perfectly in Unity. Here is my personal solution:
I put a black panel below every other GUI, so that it darkens my entire screen.
I put an empty game object called BrightRoot below the panel, so that everything under BrightRoot will float over and "brightened".
In my tutorial script, I add function to look for a UI game object by name and change its parent to the BrightRoot. In example:
// To brighten the object
GameObject button = GameObject.Find("PlayButton");
Tansform oldParent = button.transform.parent;
button.transform.SetParent(BrightRoot, true);
// To darken it again
button.transform.SetParent(oldParent, true);
The perfect solution would be to write a UI shader that darken any pixel outside some rectangles and brighten the inside. Then set that shader to all UI objects.
Editted:
This just another easy method, using UI Vertex effect. Just need to implement IsPointInsideClipRect, put this component to your UI objects, and set the rectangles list:
using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using UnityEngine.UI;
[AddComponentMenu("UI/Effects/Clip")]
public class Clip : BaseVertexEffect
{
// We need list of rectangles here - can be an array of RectTransform
public RectTransform[] ClipRects;
public override void ModifyVertices(List<UIVertex> vertexList)
{
if (!IsActive())
{
return;
}
bool isClipped = true;
for (int i = 0; i < count; i++)
{
UIVertex uiVertex = vertexList[i];
foreach (RectTransform rect in ClipRects)
{
if (IsPointInsideClipRect(rect, uiVertex.position))
{
isClipped = false;
break;
}
}
}
Color32 color = isClipped ? new Color32(0.5f, 0.5f, 0.5f, 0.5f) : new Color(1.0f, 1.0f, 1.0f, 1.0f);
for (int i = 0; i < count; i++)
{
UIVertex uiVertex = vertexList[i];
uiVertex.color = color;
}
}
private static bool IsPointInsideClipRect(RectTransform rect, Vector3 position)
{
// ...
}
}