Example of using OpenGL ES shaders to simulate static TV-noise style animation.

FragmentShader

//
//  Shader.fsh
//  ExampleGL
//
//  Created by Daniel Jalkut on 1/6/12.
//  Copyright (c) 2012 Red Sweater Software. All rights reserved.
//

// The idea for this GL-based noise shader was inspired by Mike Ash when I was chatting with him about
// how I could more efficiently generate the random noise updates to a UIView.

// Comes from the vertex shader
varying highp vec4 positionInput;

// Come from the client app
uniform highp float randomInput;

highp float rand(highp vec2 co)
{
  // I got this technique online ... don't know if there is anything magical about the constants
	// or if it's just thrown in junk...
    highp float returnVal = fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
	return returnVal;
}

void main()
{
	highp float grayComponent = rand(vec2(positionInput.x + randomInput, positionInput.y + randomInput));
    gl_FragColor = vec4(grayComponent, grayComponent, grayComponent, 1.0);
}

VertexSha

//
//  Shader.vsh
//  ExampleGL
//
//  Created by Daniel Jalkut on 1/6/12.
//  Copyright (c) 2012 Red Sweater Software. All rights reserved.
//

attribute vec4 position;
varying highp vec4 positionInput;

void main()
{
  positionInput = position;
    gl_Position = position;
}