Shader change problem

Graphics Shaders & Materials
1

I don’t know why this code does not work.

Error says ,

NullReferenceException
UI.UpdateHotkeys () (at Assets\Scripts\UI\UI.js:301)
UI.Update () (at Assets\Scripts\UI\UI.js:68)

private var rend : Transform;
function Start(){
	rend = transform.Find("Bip01_Pelvis");
}

function Update(){
if(Input.GetKeyDown("1"))
	{
var rendshad : Renderer = rend.GetComponent(Renderer);

rendshad.material.shader = Shader.Find("Particles/Additive");	 
	}	
}

Bip01_Pelvis has two Materials, I want to change them all or just second one.

2

And how to access to second or third, materials?

In case of renderer has many materials.

3

This solved.

Another q.

How to preserve the current shader set? (e.g. Diffuse)

For usage of backwards to preserved shader after change to another set.

4

There is actually a shader class defined, so you can store a reference to the shader in a variable. If you need to change shaders several times but then backtrack to whatever you were using previously, then a stack data structure might be what you need.