Gerstner wave implementation in HLSL based on GPU Gems

gerstner_wave.hlsl

struct Wave
{
	float2 dir;
	float amplitude;
	float waveLength;
};

cbuffer cb2 : register(b2)
{
	Wave waves[100];
};

static int numWaves = 20;
static float steepness = 0.8;
static float speed = 15;

float3 CalcGerstnerWaveOffset(float3 v)
{
	float3 sum = float3(0, 0, 0);
	[unroll]
	for (int i = 0; i < numWaves; i++)
	{
		Wave wave = waves[i];
		float wi = 2 / wave.waveLength;
		float Qi = steepness / (wave.amplitude * wi * numWaves);
		float phi = speed * wi;
		float rad = dot(wave.dir, v.xz) * wi + g_time * phi;
		sum.y += sin(rad) * wave.amplitude;
		sum.xz += cos(rad) * wave.amplitude * Qi * wave.dir;
	}
	return sum;
}