MotionSmear.cginc

inline float inverselerp(float min, float max, float x)
{
	return (x - min) / (max - min);
}

float hash(float n)
{
	return frac(sin(n)*43758.5453);
}

float noise(float3 v)
{
	// The noise function returns a value in the range -1.0f -> 1.0f

	float3 p = floor(v);
	float3 f = frac(v);

	f = f*f*(3.0 - 2.0*f);
	float n = p.x + p.y*57.0 + 113.0*p.z;

	return lerp(lerp(lerp(hash(n + 0.0), hash(n + 1.0), f.x),
		lerp(hash(n + 57.0), hash(n + 58.0), f.x), f.y),
		lerp(lerp(hash(n + 113.0), hash(n + 114.0), f.x),
		lerp(hash(n + 170.0), hash(n + 171.0), f.x), f.y), f.z);
}

half4 getSmearedWorldPos(half4 vertPos)
{
	half4 worldPos = mul(unity_ObjectToWorld, vertPos);

	half3 worldOffset = _SmearPosition.xyz - _PrevSmearPosition.xyz;
	half3 localOffset = worldPos.xyz - _SmearPosition.xyz;

	// World offset should only be behind swing
	half dirDot = dot(normalize(worldOffset), normalize(localOffset));
	worldOffset = clamp(worldOffset, -_NoiseHeight, _NoiseHeight);
	worldOffset *= -clamp(dirDot, -1, 0) * (1 - step(length(worldOffset), 0));

	// World offset is scaled by distance from smearPos
	half dist = clamp(length(localOffset), _SmearRange, _SmearRange + _SmearFalloff);
	half distAlpha = inverselerp(_SmearRange + _SmearFalloff, _SmearRange, dist);
	worldOffset *= distAlpha;

	half3 smearOffset = -worldOffset.xyz * lerp(1, cheapVertNoise(worldPos * _NoiseScale), step(0, _NoiseScale));
	worldPos.xyz += smearOffset;

	return worldPos;
}