Shader - Noise

//
// Simple passthrough fragment shader
//
varying vec2 v_vTexcoord;
varying vec4 v_vColour;
varying vec2 v_vPosition;
uniform float u_time;

float rand (vec2 p){
    return fract(cos(dot(p, vec2(5.237, 6.378)))*8463.648);
}

void main()
{
    gl_FragColor = v_vColour * texture2D( gm_BaseTexture, v_vTexcoord );
    gl_FragColor *= vec4(vec3(rand(v_vPosition*u_time)), 1.0);
}



//
// Simple passthrough vertex shader
//
attribute vec3 in_Position;                  // (x,y,z)
//attribute vec3 in_Normal;                  // (x,y,z)     unused in this shader.
attribute vec4 in_Colour;                    // (r,g,b,a)
attribute vec2 in_TextureCoord;              // (u,v)

varying vec2 v_vTexcoord;
varying vec4 v_vColour;
varying vec2 v_vPosition;

void main()
{
    vec4 object_space_pos = vec4( in_Position.x, in_Position.y, in_Position.z, 1.0);
    gl_Position = gm_Matrices[MATRIX_WORLD_VIEW_PROJECTION] * object_space_pos;

    v_vColour = in_Colour;
    v_vTexcoord = in_TextureCoord;
    v_vPosition = in_Position.xy;
}


// DRAW CODE

var uTime = shader_get_uniform(shdNoise, "u_time");
shader_set(shdNoise);
shader_set_uniform(uTime, current_time/5000);
//drawstuff();
shader_reset();