SimpleDeterministicPixelNoiseCS.hlsl

RWTexture2D<float3> tex : register(u0);

// Algorithm "xor" from p. 4 of Marsaglia, "Xorshift RNGs", copied in from Wikipedia
uint Xorshift(uint seed)
{
    uint x = seed;
    x ^= x << 13;
    x ^= x >> 17;
    x ^= x << 5;
    return x;
}

static const float primes[13] =
{
    6143,
    6229,
    6311,
    6373,
    6481,
    6577,
    6679,
    6763,
    6841,
    6947,
    7001,
    7109,
    7211
};

uint ComputeSeed(uint3 DTid)
{
    return
        DTid.x * primes[DTid.x % 13] +
        DTid.y * primes[12 - DTid.y % 13];
}

[numthreads(1, 1, 1)]
void main(uint3 DTid : SV_DispatchThreadID)
{
    uint r = Xorshift(ComputeSeed(DTid));
    uint g = Xorshift(r);
    uint b = Xorshift(g);

    tex[DTid.xy] = float3(r, g, b) / 0xFFFFFFFF;
}

Now reimplemented for WebGL, too:

https://cyos.babylonjs.com/#DJDWJP