opengl es 2.0 - GLSL noise function on devices with no high precision fragment shader -

i'm looking noise function wich working on none highp fragment shader.

what have tried:

//http://stackoverflow.com/questions/4200224/random-noise-functions-for-glsl float snoise(vec2 co) {     return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453); }   //http://byteblacksmith.com/improvements-to-the-canonical-one-liner-glsl-rand-for-opengl-es-2-0/ float snoise(vec2 co) {     float = 12.9898;     float b = 78.233;     float c = 43758.5453;     float dt= dot(co.xy ,vec2(a,b));     float sn= mod(dt,3.14);     return fract(sin(sn) * c); } 

main:

void main() {     vec4 texcol = texture2d(utexdiffuse, vtexcoord.xy);      float n = snoise(vec2(vtexcoord.x*cos(utime),vtexcoord.y*sin(utime)));       gl_fragcolor = texcol;     gl_fragcolor.rgb *= n; } 

both working fine on device supports high point fragmentshader precision. on device nexus 7 not working.

i tried shader repository: webgl-noise not working.

result on highp supporting fragment shader (looking fine):

result on nexus 7 2012: