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//* 1.0.1 - using absolute import paths when importing standard modules

mdl 1.6;

import ::df::*;
import ::state::*;
import ::math::*;
import ::tex::*;
import ::anno::*;


export float3 convert_to_left_hand(float3 vec3, uniform bool up_z = true, uniform bool is_position = true)
[[
    anno::description("convert from RH to LH"),
	anno::noinline()
]]
{
	float4x4 ZupConversion = float4x4(
		1.0f, 0.0f, 0.0f, 0.0f,
		0.0f, -1.0f, 0.0f, 0.0f,
		0.0f, 0.0f, 1.0f, 0.0f,
		0.0f, 0.0f, 0.0f, 1.0f
	);

	float4x4 YupConversion = float4x4(
		1.0f, 0.0f, 0.0f, 0.0f,
		0.0f, 0.0f, 1.0f, 0.0f,
		0.0f, 1.0f, 0.0f, 0.0f,
		0.0f, 0.0f, 0.0f, 1.0f
	);

	float4 vec4 = float4(vec3.x, vec3.y, vec3.z, is_position ? 1.0f : 0.0f);

	vec4 = vec4 * (up_z ? ZupConversion : YupConversion);

	return float3(vec4.x, vec4.y, vec4.z);
}

export float3 transform_vector_from_tangent_to_world(float3 vector, 
													uniform bool up_z = true, 
													float3 tangent_u = state::texture_tangent_u(0),
    												float3 tangent_v = state::texture_tangent_v(0))
[[
    anno::description("Transform vector from tangent space to world space"),
    anno::noinline()
]]
{
	/* flip_tangent_v */
    return  convert_to_left_hand(
			tangent_u * vector.x - tangent_v * vector.y + state::normal() * vector.z, 
			up_z, false);
}

export float3 transform_vector_from_world_to_tangent(float3 vector, 
													uniform bool up_z = true,
													float3 tangent_u = state::texture_tangent_u(0),
													float3 tangent_v = state::texture_tangent_v(0))
[[
    anno::description("Transform vector from world space to tangent space"),
    anno::noinline()
]]
{
	float3 vecRH = convert_to_left_hand(vector, up_z, false);
	/* flip_tangent_v */
	return 	vecRH.x * float3(tangent_u.x, -tangent_v.x, state::normal().x) +
        	vecRH.y * float3(tangent_u.y, -tangent_v.y, state::normal().y) +
        	vecRH.z * float3(tangent_u.z, -tangent_v.z, state::normal().z);
}

export float4 unpack_normal_map(
    float4 texture_sample = float4(0.0, 0.0, 1.0, 1.0)
    )
[[
    anno::description("Unpack a normal stored in a normal map"),
    anno::noinline()
]]
{
    float2 normal_xy = float2(texture_sample.x, texture_sample.y);

	normal_xy = normal_xy * float2(2.0,2.0) - float2(1.0,1.0);
	float normal_z = math::sqrt( math::saturate( 1.0 - math::dot( normal_xy, normal_xy ) ) );
	return float4( normal_xy.x, normal_xy.y, normal_z, 1.0 );
}

// for get color value from normal.
export float4 pack_normal_map(
    float4 texture_sample = float4(0.0, 0.0, 1.0, 1.0)
    )
[[
    anno::description("Pack to color from a normal")
]]
{
    float2 return_xy = float2(texture_sample.x, texture_sample.y);

	return_xy = (return_xy + float2(1.0,1.0)) / float2(2.0,2.0);
	
	return float4( return_xy.x, return_xy.y, 0.0, 1.0 );
}

export float4 greyscale_texture_lookup(
    float4 texture_sample = float4(0.0, 0.0, 0.0, 1.0)
    )
[[
    anno::description("Sampling a greyscale texture"),
    anno::noinline()
]]
{
    return float4(texture_sample.x, texture_sample.x, texture_sample.x, texture_sample.x);
}     

export float3 pixel_normal_world_space(uniform bool up_z = true)
[[
    anno::description("Pixel normal in world space"),
    anno::noinline()
]]
{
    return convert_to_left_hand(state::transform_normal(state::coordinate_internal,state::coordinate_world,state::normal()), up_z, false);
}

export float3 vertex_normal_world_space(uniform bool up_z = true)
[[
    anno::description("Vertex normal in world space"),
    anno::noinline()
]]
{
    return convert_to_left_hand(state::transform_normal(state::coordinate_internal,state::coordinate_world,state::normal()), up_z, false);
}

export float3 landscape_normal_world_space(uniform bool up_z = true)
[[
    anno::description("Landscape normal in world space")
]]
{
	float3 normalFromNormalmap = math::floor((::vertex_normal_world_space(up_z) * 0.5 + 0.5) * 255.0) / 255.0 * 2.0 - 1.0;
	
	float2 normalXY = float2(normalFromNormalmap.x, normalFromNormalmap.y);
	return float3(normalXY.x, normalXY.y, math::sqrt(math::saturate(1.0 - math::dot(normalXY, normalXY))));
}

// Different implementation specific between mdl and hlsl for smoothstep
export float smoothstep(float a, float b, float l)
{
	if (a < b)
	{
		return math::smoothstep(a, b, l);
	}
	else if (a > b)
	{
		return 1.0 - math::smoothstep(b, a, l);
	}
	else
	{
		return l <= a ? 0.0 : 1.0;
	}
}

export float2 smoothstep(float2 a, float2 b, float2 l)
{
	return float2(smoothstep(a.x, b.x, l.x), smoothstep(a.y, b.y, l.y));
}

export float3 smoothstep(float3 a, float3 b, float3 l)
{
	return float3(smoothstep(a.x, b.x, l.x), smoothstep(a.y, b.y, l.y), smoothstep(a.z, b.z, l.z));
}

export float4 smoothstep(float4 a, float4 b, float4 l)
{
	return float4(smoothstep(a.x, b.x, l.x), smoothstep(a.y, b.y, l.y), smoothstep(a.z, b.z, l.z), smoothstep(a.w, b.w, l.w));
}

export float2 smoothstep(float2 a, float2 b, float l)
{
	return float2(smoothstep(a.x, b.x, l), smoothstep(a.y, b.y, l));
}

export float3 smoothstep(float3 a, float3 b, float l)
{
	return float3(smoothstep(a.x, b.x, l), smoothstep(a.y, b.y, l), smoothstep(a.z, b.z, l));
}

export float4 smoothstep(float4 a, float4 b, float l)
{
	return float4(smoothstep(a.x, b.x, l), smoothstep(a.y, b.y, l), smoothstep(a.z, b.z, l), smoothstep(a.w, b.w, l));
}

export float2 smoothstep(float a, float b, float2 l)
{
	return float2(smoothstep(a, b, l.x), smoothstep(a, b, l.y));
}

export float3 smoothstep(float a, float b, float3 l)
{
	return float3(smoothstep(a, b, l.x), smoothstep(a, b, l.y), smoothstep(a, b, l.z));
}

export float4 smoothstep(float a, float b, float4 l)
{
	return float4(smoothstep(a, b, l.x), smoothstep(a, b, l.y), smoothstep(a, b, l.z), smoothstep(a, b, l.w));
}

//------------------ Random from UE4 -----------------------
float length2(float3 v)
{
	return math::dot(v, v);
}

float3 GetPerlinNoiseGradientTextureAt(uniform texture_2d PerlinNoiseGradientTexture, float3 v)
{
	const float2 ZShear = float2(17.0f, 89.0f);

	float2 OffsetA = v.z * ZShear;
	float2 TexA = (float2(v.x, v.y) + OffsetA + 0.5f) / 128.0f;
	float4 PerlinNoise = tex::lookup_float4(PerlinNoiseGradientTexture,float2(TexA.x,1.0-TexA.y),tex::wrap_repeat,tex::wrap_repeat);
	return float3(PerlinNoise.x, PerlinNoise.y, PerlinNoise.z) * 2.0 - 1.0;
}

float3 SkewSimplex(float3 In)
{
	return In + math::dot(In, float3(1.0 / 3.0f) );
}
float3 UnSkewSimplex(float3 In)
{
	return In - math::dot(In, float3(1.0 / 6.0f) );
}

// 3D random number generator inspired by PCGs (permuted congruential generator)
// Using a **simple** Feistel cipher in place of the usual xor shift permutation step
// @param v = 3D integer coordinate
// @return three elements w/ 16 random bits each (0-0xffff).
// ~8 ALU operations for result.x    (7 mad, 1 >>)
// ~10 ALU operations for result.xy  (8 mad, 2 >>)
// ~12 ALU operations for result.xyz (9 mad, 3 >>)

//TODO: uint3
int3 Rand3DPCG16(int3 p)
{
	// taking a signed int then reinterpreting as unsigned gives good behavior for negatives
	//TODO: uint3
	int3 v = int3(p);

	// Linear congruential step. These LCG constants are from Numerical Recipies
	// For additional #'s, PCG would do multiple LCG steps and scramble each on output
	// So v here is the RNG state
	v = v * 1664525 + 1013904223;

	// PCG uses xorshift for the final shuffle, but it is expensive (and cheap
	// versions of xorshift have visible artifacts). Instead, use simple MAD Feistel steps
	//
	// Feistel ciphers divide the state into separate parts (usually by bits)
	// then apply a series of permutation steps one part at a time. The permutations
	// use a reversible operation (usually ^) to part being updated with the result of
	// a permutation function on the other parts and the key.
	//
	// In this case, I'm using v.x, v.y and v.z as the parts, using + instead of ^ for
	// the combination function, and just multiplying the other two parts (no key) for 
	// the permutation function.
	//
	// That gives a simple mad per round.
	v.x += v.y*v.z;
	v.y += v.z*v.x;
	v.z += v.x*v.y;
	v.x += v.y*v.z;
	v.y += v.z*v.x;
	v.z += v.x*v.y;

	// only top 16 bits are well shuffled
	return v >> 16;
}

// Wraps noise for tiling texture creation
// @param v = unwrapped texture parameter
// @param bTiling = true to tile, false to not tile
// @param RepeatSize = number of units before repeating
// @return either original or wrapped coord
float3 NoiseTileWrap(float3 v,  bool bTiling, float RepeatSize)
{
	return bTiling ? (math::frac(v / RepeatSize) * RepeatSize) : v;
}

// Evaluate polynomial to get smooth transitions for Perlin noise
// only needed by Perlin functions in this file
// scalar(per component): 2 add, 5 mul
float4 PerlinRamp(float4 t)
{
	return t * t * t * (t * (t * 6 - 15) + 10); 
}

// Blum-Blum-Shub-inspired pseudo random number generator
// http://www.umbc.edu/~olano/papers/mNoise.pdf
// real BBS uses ((s*s) mod M) with bignums and M as the product of two huge Blum primes
// instead, we use a single prime M just small enough not to overflow
// note that the above paper used 61, which fits in a half, but is unusably bad
// @param Integer valued floating point seed
// @return random number in range [0,1)
// ~8 ALU operations (5 *, 3 frac)
float RandBBSfloat(float seed)
{
	float BBS_PRIME24 = 4093.0;
	float s = math::frac(seed / BBS_PRIME24);
	s = math::frac(s * s * BBS_PRIME24);
	s = math::frac(s * s * BBS_PRIME24);
	return s;
}

// Modified noise gradient term
// @param seed - random seed for integer lattice position
// @param offset - [-1,1] offset of evaluation point from lattice point
// @return gradient direction (xyz) and contribution (w) from this lattice point
float4 MGradient(int seed, float3 offset)
{
	//TODO uint
	int rand = Rand3DPCG16(int3(seed,0,0)).x;
	int3 MGradientMask = int3(0x8000, 0x4000, 0x2000);
	float3 MGradientScale = float3(1.0 / 0x4000, 1.0 / 0x2000, 1.0 / 0x1000);
	float3 direction = float3(int3(rand, rand, rand) & MGradientMask) * MGradientScale - 1;
	return float4(direction.x, direction.y, direction.z, math::dot(direction, offset));
}

// compute Perlin and related noise corner seed values
// @param v = 3D noise argument, use float3(x,y,0) for 2D or float3(x,0,0) for 1D
// @param bTiling = true to return seed values for a repeating noise pattern
// @param RepeatSize = integer units before tiling in each dimension
// @param seed000-seed111 = hash function seeds for the eight corners
// @return fractional part of v
struct SeedValue
{
	float3 fv = float3(0);
	float seed000 = 0;
	float seed001 = 0;
	float seed010 = 0;
	float seed011 = 0;
	float seed100 = 0;
	float seed101 = 0;
	float seed110 = 0;
	float seed111 = 0;
};

SeedValue NoiseSeeds(float3 v, bool bTiling, float RepeatSize)
{
	SeedValue seeds;
	seeds.fv = math::frac(v);
	float3 iv = math::floor(v);

	const float3 primes = float3(19, 47, 101);

	if (bTiling)
	{	// can't algebraically combine with primes
		seeds.seed000 = math::dot(primes, NoiseTileWrap(iv, true, RepeatSize));
		seeds.seed100 = math::dot(primes, NoiseTileWrap(iv + float3(1, 0, 0), true, RepeatSize));
		seeds.seed010 = math::dot(primes, NoiseTileWrap(iv + float3(0, 1, 0), true, RepeatSize));
		seeds.seed110 = math::dot(primes, NoiseTileWrap(iv + float3(1, 1, 0), true, RepeatSize));
		seeds.seed001 = math::dot(primes, NoiseTileWrap(iv + float3(0, 0, 1), true, RepeatSize));
		seeds.seed101 = math::dot(primes, NoiseTileWrap(iv + float3(1, 0, 1), true, RepeatSize));
		seeds.seed011 = math::dot(primes, NoiseTileWrap(iv + float3(0, 1, 1), true, RepeatSize));
		seeds.seed111 = math::dot(primes, NoiseTileWrap(iv + float3(1, 1, 1), true, RepeatSize));
	}
	else
	{	// get to combine offsets with multiplication by primes in this case
		seeds.seed000 = math::dot(iv, primes);
		seeds.seed100 = seeds.seed000 + primes.x;
		seeds.seed010 = seeds.seed000 + primes.y;
		seeds.seed110 = seeds.seed100 + primes.y;
		seeds.seed001 = seeds.seed000 + primes.z;
		seeds.seed101 = seeds.seed100 + primes.z;
		seeds.seed011 = seeds.seed010 + primes.z;
		seeds.seed111 = seeds.seed110 + primes.z;
	}

	return seeds;
}

struct SimplexWeights
{
	float4 Result = float4(0);
	float3 PosA = float3(0);
	float3 PosB = float3(0);
	float3 PosC = float3(0);
	float3 PosD = float3(0);
};

// Computed weights and sample positions for simplex interpolation
// @return float4(a,b,c, d) Barycentric coordinate defined as Filtered = Tex(PosA) * a + Tex(PosB) * b + Tex(PosC) * c + Tex(PosD) * d
SimplexWeights ComputeSimplexWeights3D(float3 OrthogonalPos)
{
	SimplexWeights weights;
	float3 OrthogonalPosFloor = math::floor(OrthogonalPos);

	weights.PosA = OrthogonalPosFloor;
	weights.PosB = weights.PosA + float3(1, 1, 1);

	OrthogonalPos -= OrthogonalPosFloor;

	float Largest = math::max(OrthogonalPos.x, math::max(OrthogonalPos.y, OrthogonalPos.z));
	float Smallest = math::min(OrthogonalPos.x, math::min(OrthogonalPos.y, OrthogonalPos.z));

	weights.PosC = weights.PosA + float3(Largest == OrthogonalPos.x, Largest == OrthogonalPos.y, Largest == OrthogonalPos.z);
	weights.PosD = weights.PosA + float3(Smallest != OrthogonalPos.x, Smallest != OrthogonalPos.y, Smallest != OrthogonalPos.z);

	float RG = OrthogonalPos.x - OrthogonalPos.y;
	float RB = OrthogonalPos.x - OrthogonalPos.z;
	float GB = OrthogonalPos.y - OrthogonalPos.z;

	weights.Result.z = 
		  math::min(math::max(0, RG), math::max(0, RB))		// X
		+ math::min(math::max(0, -RG), math::max(0, GB))		// Y
		+ math::min(math::max(0, -RB), math::max(0, -GB));	// Z
	
	weights.Result.w = 
		  math::min(math::max(0, -RG), math::max(0, -RB))		// X
		+ math::min(math::max(0, RG), math::max(0, -GB))		// Y
		+ math::min(math::max(0, RB), math::max(0, GB));		// Z

	weights.Result.y = Smallest;
	weights.Result.x = 1.0f - weights.Result.y - weights.Result.z - weights.Result.w;

	return weights;
}

// filtered 3D gradient simple noise (few texture lookups, high quality)
// @param v >0
// @return random number in the range -1 .. 1
float SimplexNoise3D_TEX(uniform texture_2d PerlinNoiseGradientTexture, float3 EvalPos)
{
	float3 OrthogonalPos = SkewSimplex(EvalPos);

	SimplexWeights Weights = ComputeSimplexWeights3D(OrthogonalPos);

	// can be optimized to 1 or 2 texture lookups (4 or 8 channel encoded in 32 bit)
	float3 A = GetPerlinNoiseGradientTextureAt(PerlinNoiseGradientTexture, Weights.PosA);
	float3 B = GetPerlinNoiseGradientTextureAt(PerlinNoiseGradientTexture, Weights.PosB);
	float3 C = GetPerlinNoiseGradientTextureAt(PerlinNoiseGradientTexture, Weights.PosC);
	float3 D = GetPerlinNoiseGradientTextureAt(PerlinNoiseGradientTexture, Weights.PosD);
	
	Weights.PosA = UnSkewSimplex(Weights.PosA);
	Weights.PosB = UnSkewSimplex(Weights.PosB);
	Weights.PosC = UnSkewSimplex(Weights.PosC);
	Weights.PosD = UnSkewSimplex(Weights.PosD);

	float DistanceWeight;

	DistanceWeight = math::saturate(0.6f - length2(EvalPos - Weights.PosA));	DistanceWeight *= DistanceWeight; DistanceWeight *= DistanceWeight;
	float a = math::dot(A, EvalPos - Weights.PosA) * DistanceWeight;
	DistanceWeight = math::saturate(0.6f - length2(EvalPos - Weights.PosB));	DistanceWeight *= DistanceWeight; DistanceWeight *= DistanceWeight;
	float b = math::dot(B, EvalPos - Weights.PosB) * DistanceWeight;
	DistanceWeight = math::saturate(0.6f - length2(EvalPos - Weights.PosC));	DistanceWeight *= DistanceWeight; DistanceWeight *= DistanceWeight;
	float c = math::dot(C, EvalPos - Weights.PosC) * DistanceWeight;
	DistanceWeight = math::saturate(0.6f - length2(EvalPos - Weights.PosD));	DistanceWeight *= DistanceWeight; DistanceWeight *= DistanceWeight;
	float d = math::dot(D, EvalPos - Weights.PosD) * DistanceWeight;

	return 32 * (a + b + c + d);
}

// filtered 3D noise, can be optimized
// @param v = 3D noise argument, use float3(x,y,0) for 2D or float3(x,0,0) for 1D
// @param bTiling = repeat noise pattern
// @param RepeatSize = integer units before tiling in each dimension
// @return random number in the range -1 .. 1
float GradientNoise3D_TEX(uniform texture_2d PerlinNoiseGradientTexture, float3 v, bool bTiling, float RepeatSize)
{
	bTiling = true;
	float3 fv = math::frac(v);
	float3 iv0 = NoiseTileWrap(math::floor(v), bTiling, RepeatSize);
	float3 iv1 = NoiseTileWrap(iv0 + 1, bTiling, RepeatSize);

	const int2 ZShear = int2(17, 89);
	
	float2 OffsetA = iv0.z * ZShear;
	float2 OffsetB = OffsetA + ZShear;	// non-tiling, use relative offset
	if (bTiling)						// tiling, have to compute from wrapped coordinates
	{
		OffsetB = iv1.z * ZShear;
	}

	// Texture size scale factor
	float ts = 1 / 128.0f;

	// texture coordinates for iv0.xy, as offset for both z slices
	float2 TexA0 = (float2(iv0.x, iv0.y) + OffsetA + 0.5f) * ts;
	float2 TexB0 = (float2(iv0.x, iv0.y) + OffsetB + 0.5f) * ts;

	// texture coordinates for iv1.xy, as offset for both z slices
	float2 TexA1 = TexA0 + ts;	// for non-tiling, can compute relative to existing coordinates
	float2 TexB1 = TexB0 + ts;
	if (bTiling)				// for tiling, need to compute from wrapped coordinates
	{
		TexA1 = (float2(iv1.x, iv1.y) + OffsetA + 0.5f) * ts;
		TexB1 = (float2(iv1.x, iv1.y) + OffsetB + 0.5f) * ts;
	}


	// can be optimized to 1 or 2 texture lookups (4 or 8 channel encoded in 8, 16 or 32 bit)
	float4 PerlinNoise = tex::lookup_float4(PerlinNoiseGradientTexture,float2(TexA0.x,1.0-TexA0.y),tex::wrap_repeat,tex::wrap_repeat);
	float3 PerlinNoiseColor = float3(PerlinNoise.x, PerlinNoise.y, PerlinNoise.z);
	float3 A = PerlinNoiseColor * 2 - 1;
	PerlinNoise = tex::lookup_float4(PerlinNoiseGradientTexture,float2(TexA1.x,1.0-TexA0.y),tex::wrap_repeat,tex::wrap_repeat);
	PerlinNoiseColor = float3(PerlinNoise.x, PerlinNoise.y, PerlinNoise.z);
	float3 B = PerlinNoiseColor * 2 - 1;
	PerlinNoise = tex::lookup_float4(PerlinNoiseGradientTexture,float2(TexA0.x,1.0-TexA1.y),tex::wrap_repeat,tex::wrap_repeat);
	PerlinNoiseColor = float3(PerlinNoise.x, PerlinNoise.y, PerlinNoise.z);
	float3 C = PerlinNoiseColor * 2 - 1;
	PerlinNoise = tex::lookup_float4(PerlinNoiseGradientTexture,float2(TexA1.x,1.0-TexA1.y),tex::wrap_repeat,tex::wrap_repeat);
	PerlinNoiseColor = float3(PerlinNoise.x, PerlinNoise.y, PerlinNoise.z);
	float3 D = PerlinNoiseColor * 2 - 1;
	PerlinNoise = tex::lookup_float4(PerlinNoiseGradientTexture,float2(TexB0.x,1.0-TexB0.y),tex::wrap_repeat,tex::wrap_repeat);
	PerlinNoiseColor = float3(PerlinNoise.x, PerlinNoise.y, PerlinNoise.z);
	float3 E = PerlinNoiseColor * 2 - 1;
	PerlinNoise = tex::lookup_float4(PerlinNoiseGradientTexture,float2(TexB1.x,1.0-TexB0.y),tex::wrap_repeat,tex::wrap_repeat);
	PerlinNoiseColor = float3(PerlinNoise.x, PerlinNoise.y, PerlinNoise.z);
	float3 F = PerlinNoiseColor * 2 - 1;
	PerlinNoise = tex::lookup_float4(PerlinNoiseGradientTexture,float2(TexB0.x,1.0-TexB1.y),tex::wrap_repeat,tex::wrap_repeat);
	PerlinNoiseColor = float3(PerlinNoise.x, PerlinNoise.y, PerlinNoise.z);
	float3 G = PerlinNoiseColor * 2 - 1;
	PerlinNoise = tex::lookup_float4(PerlinNoiseGradientTexture,float2(TexB1.x,1.0-TexB1.y),tex::wrap_repeat,tex::wrap_repeat);
	PerlinNoiseColor = float3(PerlinNoise.x, PerlinNoise.y, PerlinNoise.z);
	float3 H = PerlinNoiseColor * 2 - 1;

	float a = math::dot(A, fv - float3(0, 0, 0));
	float b = math::dot(B, fv - float3(1, 0, 0));
	float c = math::dot(C, fv - float3(0, 1, 0));
	float d = math::dot(D, fv - float3(1, 1, 0));
	float e = math::dot(E, fv - float3(0, 0, 1));
	float f = math::dot(F, fv - float3(1, 0, 1));
	float g = math::dot(G, fv - float3(0, 1, 1));
	float h = math::dot(H, fv - float3(1, 1, 1));

	float4 Weights = PerlinRamp(math::frac(float4(fv.x, fv.y, fv.z, 0)));
	
	float i = math::lerp(math::lerp(a, b, Weights.x), math::lerp(c, d, Weights.x), Weights.y);
	float j = math::lerp(math::lerp(e, f, Weights.x), math::lerp(g, h, Weights.x), Weights.y);

	return math::lerp(i, j, Weights.z);
}

// @return random number in the range -1 .. 1
// scalar: 6 frac, 31 mul/mad, 15 add, 
float FastGradientPerlinNoise3D_TEX(uniform texture_3d PerlinNoise3DTexture, float3 xyz)
{
	// needs to be the same value when creating the PerlinNoise3D texture
	float Extent = 16;

	// last texel replicated and needed for filtering
	// scalar: 3 frac, 6 mul
	xyz = math::frac(xyz / (Extent - 1)) * (Extent - 1);

	// scalar: 3 frac
	float3 uvw = math::frac(xyz);
	// = floor(xyz);
	// scalar: 3 add
	float3 p0 = xyz - uvw;
//	float3 f = math::pow(uvw, 2) * 3.0f - math::pow(uvw, 3) * 2.0f;	// original perlin hermite (ok when used without bump mapping)
	// scalar: 2*3 add 5*3 mul
	float4 pr = PerlinRamp(float4(uvw.x, uvw.y, uvw.z, 0));
	float3 f = float3(pr.x, pr.y, pr.z);	// new, better with continues second derivative for bump mapping
	// scalar: 3 add
	float3 p = p0 + f;
	// scalar: 3 mad
	// TODO: need reverse???
	float4 NoiseSample = tex::lookup_float4(PerlinNoise3DTexture, p / Extent + 0.5f / Extent);	// +0.5f to get rid of bilinear offset

	// reconstruct from 8bit (using mad with 2 constants and dot4 was same instruction count)
	// scalar: 4 mad, 3 mul, 3 add 
	float3 n = float3(NoiseSample.x, NoiseSample.y, NoiseSample.z) * 255.0f / 127.0f - 1.0f;
	float d = NoiseSample.w * 255.f - 127;
	return math::dot(xyz, n) - d;
}

// Perlin-style "Modified Noise"
// http://www.umbc.edu/~olano/papers/index.html#mNoise
// @param v = 3D noise argument, use float3(x,y,0) for 2D or float3(x,0,0) for 1D
// @param bTiling = repeat noise pattern
// @param RepeatSize = integer units before tiling in each dimension
// @return random number in the range -1 .. 1
float GradientNoise3D_ALU(float3 v, bool bTiling, float RepeatSize)
{
	SeedValue seeds = NoiseSeeds(v, bTiling, RepeatSize);

	float rand000 = MGradient(int(seeds.seed000), seeds.fv - float3(0, 0, 0)).w;
	float rand100 = MGradient(int(seeds.seed100), seeds.fv - float3(1, 0, 0)).w;
	float rand010 = MGradient(int(seeds.seed010), seeds.fv - float3(0, 1, 0)).w;
	float rand110 = MGradient(int(seeds.seed110), seeds.fv - float3(1, 1, 0)).w;
	float rand001 = MGradient(int(seeds.seed001), seeds.fv - float3(0, 0, 1)).w;
	float rand101 = MGradient(int(seeds.seed101), seeds.fv - float3(1, 0, 1)).w;
	float rand011 = MGradient(int(seeds.seed011), seeds.fv - float3(0, 1, 1)).w;
	float rand111 = MGradient(int(seeds.seed111), seeds.fv - float3(1, 1, 1)).w;

	float4 Weights = PerlinRamp(float4(seeds.fv.x, seeds.fv.y, seeds.fv.z, 0));

	float i = math::lerp(math::lerp(rand000, rand100, Weights.x), math::lerp(rand010, rand110, Weights.x), Weights.y);
	float j = math::lerp(math::lerp(rand001, rand101, Weights.x), math::lerp(rand011, rand111, Weights.x), Weights.y);
	return math::lerp(i, j, Weights.z);
}

// 3D value noise - used to be incorrectly called Perlin noise
// @param v = 3D noise argument, use float3(x,y,0) for 2D or float3(x,0,0) for 1D
// @param bTiling = repeat noise pattern
// @param RepeatSize = integer units before tiling in each dimension
// @return random number in the range -1 .. 1
float ValueNoise3D_ALU(float3 v, bool bTiling, float RepeatSize)
{
	SeedValue seeds = NoiseSeeds(v, bTiling, RepeatSize);

	float rand000 = RandBBSfloat(seeds.seed000) * 2 - 1;
	float rand100 = RandBBSfloat(seeds.seed100) * 2 - 1;
	float rand010 = RandBBSfloat(seeds.seed010) * 2 - 1;
	float rand110 = RandBBSfloat(seeds.seed110) * 2 - 1;
	float rand001 = RandBBSfloat(seeds.seed001) * 2 - 1;
	float rand101 = RandBBSfloat(seeds.seed101) * 2 - 1;
	float rand011 = RandBBSfloat(seeds.seed011) * 2 - 1;
	float rand111 = RandBBSfloat(seeds.seed111) * 2 - 1;
	
	float4 Weights = PerlinRamp(float4(seeds.fv.x, seeds.fv.y, seeds.fv.z, 0));
	
	float i = math::lerp(math::lerp(rand000, rand100, Weights.x), math::lerp(rand010, rand110, Weights.x), Weights.y);
	float j = math::lerp(math::lerp(rand001, rand101, Weights.x), math::lerp(rand011, rand111, Weights.x), Weights.y);
	return math::lerp(i, j, Weights.z);
}

// 3D jitter offset within a voronoi noise cell
// @param pos - integer lattice corner
// @return random offsets vector
float3 VoronoiCornerSample(float3 pos, int Quality)
{
	// random values in [-0.5, 0.5]
	float3 noise = float3(Rand3DPCG16(int3(pos))) / 0xffff - 0.5;

	// quality level 1 or 2: searches a 2x2x2 neighborhood with points distributed on a sphere
	// scale factor to guarantee jittered points will be found within a 2x2x2 search
	if (Quality <= 2)
	{
		return math::normalize(noise) * 0.2588;
	}

	// quality level 3: searches a 3x3x3 neighborhood with points distributed on a sphere
	// scale factor to guarantee jittered points will be found within a 3x3x3 search
	if (Quality == 3)
	{
		return math::normalize(noise) * 0.3090;
	}

	// quality level 4: jitter to anywhere in the cell, needs 4x4x4 search
	return noise;
}

// compare previous best with a new candidate
// not producing point locations makes it easier for compiler to eliminate calculations when they're not needed
// @param minval = location and distance of best candidate seed point before the new one
// @param candidate = candidate seed point
// @param offset = 3D offset to new candidate seed point
// @param bDistanceOnly = if true, only set maxval.w with distance, otherwise maxval.w is distance and maxval.xyz is position
// @return position (if bDistanceOnly is false) and distance to closest seed point so far
float4 VoronoiCompare(float4 minval, float3 candidate, float3 offset, bool bDistanceOnly)
{
	if (bDistanceOnly)
	{
		return float4(0, 0, 0, math::min(minval.w, math::dot(offset, offset)));
	}
	else
	{
		float newdist = math::dot(offset, offset);
		return newdist > minval.w ? minval : float4(candidate.x, candidate.y, candidate.z, newdist);
	}
}

// 220 instruction Worley noise
float4 VoronoiNoise3D_ALU(float3 v, int Quality, bool bTiling, float RepeatSize, bool bDistanceOnly)
{
	float3 fv = math::frac(v),  fv2 = math::frac(v + 0.5);
	float3 iv = math::floor(v), iv2 = math::floor(v + 0.5);

	// with initial minimum distance = infinity (or at least bigger than 4), first min is optimized away
	float4 mindist = float4(0,0,0,100);
	float3 p, offset;

	// quality level 3: do a 3x3x3 search
	if (Quality == 3)
	{
		int offset_x;
		int offset_y;
		int offset_z;
		for (offset_x = -1; offset_x <= 1; ++offset_x)
		{
			for (offset_y = -1; offset_y <= 1; ++offset_y)
			{
				for (offset_z = -1; offset_z <= 1; ++offset_z)
				{
					offset = float3(offset_x, offset_y, offset_z);
					p = offset + VoronoiCornerSample(NoiseTileWrap(iv2 + offset, bTiling, RepeatSize), Quality);
					mindist = VoronoiCompare(mindist, iv2 + p, fv2 - p, bDistanceOnly);
				}
			}
		}
	}

	// everybody else searches a base 2x2x2 neighborhood
	else
	{
		int offset_x;
		int offset_y;
		int offset_z;
		for (offset_x = 0; offset_x <= 1; ++offset_x)
		{
			for (offset_y = 0; offset_y <= 1; ++offset_y)
			{
				for (offset_z = 0; offset_z <= 1; ++offset_z)
				{
					offset = float3(offset_x, offset_y, offset_z);
					p = offset + VoronoiCornerSample(NoiseTileWrap(iv + offset, bTiling, RepeatSize), Quality);
					mindist = VoronoiCompare(mindist, iv + p, fv - p, bDistanceOnly);

					// quality level 2, do extra set of points, offset by half a cell
					if (Quality == 2)
					{
						// 467 is just an offset to a different area in the random number field to avoid similar neighbor artifacts
						p = offset + VoronoiCornerSample(NoiseTileWrap(iv2 + offset, bTiling, RepeatSize) + 467, Quality);
						mindist = VoronoiCompare(mindist, iv2 + p, fv2 - p, bDistanceOnly);
					}
				}
			}
		}
	}

	// quality level 4: add extra sets of four cells in each direction
	if (Quality >= 4)
	{
		int offset_x;
		int offset_y;
		int offset_z;	
		for (offset_x = -1; offset_x <= 2; offset_x += 3)
		{
			for (offset_y = 0; offset_y <= 1; ++offset_y)
			{
				for (offset_z = 0; offset_z <= 1; ++offset_z)
				{
					offset = float3(offset_x, offset_y, offset_z);
					// along x axis
					p = offset + VoronoiCornerSample(NoiseTileWrap(iv + offset, bTiling, RepeatSize), Quality);
					mindist = VoronoiCompare(mindist, iv + p, fv - p, bDistanceOnly);

					// along y axis
					p = float3(offset.y, offset.z, offset.x) + VoronoiCornerSample(NoiseTileWrap(iv + float3(offset.y, offset.z, offset.x), bTiling, RepeatSize), Quality);
					mindist = VoronoiCompare(mindist, iv + p, fv - p, bDistanceOnly);

					// along z axis
					p = float3(offset.z, offset.x, offset.y) + VoronoiCornerSample(NoiseTileWrap(iv + float3(offset.z, offset.x, offset.y), bTiling, RepeatSize), Quality);
					mindist = VoronoiCompare(mindist, iv + p, fv - p, bDistanceOnly);
				}
			}
		}
	}

	// transform squared distance to real distance
	return float4(mindist.x, mindist.y, mindist.z, math::sqrt(mindist.w));
}

// Coordinates for corners of a Simplex tetrahedron
// Based on McEwan et al., Efficient computation of noise in GLSL, JGT 2011
// @param v = 3D noise argument
// @return 4 corner locations
float4x3 SimplexCorners(float3 v)
{
	// find base corner by skewing to tetrahedral space and back
	float3 tet = math::floor(v + v.x/3 + v.y/3 + v.z/3);
	float3 base = tet - tet.x/6 - tet.y/6 - tet.z/6;
	float3 f = v - base;

	// Find offsets to other corners (McEwan did this in tetrahedral space,
	// but since skew is along x=y=z axis, this works in Euclidean space too.)
	float3 g = math::step(float3(f.y,f.z,f.x), float3(f.x,f.y,f.z)), h = 1 - float3(g.z, g.x, g.y);
	float3 a1 = math::min(g, h) - 1.0 / 6.0, a2 = math::max(g, h) - 1.0 / 3.0;

	// four corners
	return float4x3(base, base + a1, base + a2, base + 0.5);
}

// Improved smoothing function for simplex noise
// @param f = fractional distance to four tetrahedral corners
// @return weight for each corner
float4 SimplexSmooth(float4x3 f)
{
	const float scale = 1024. / 375.;	// scale factor to make noise -1..1
	float4 d = float4(math::dot(f[0], f[0]), math::dot(f[1], f[1]), math::dot(f[2], f[2]), math::dot(f[3], f[3]));
	float4 s = math::saturate(2 * d);
	return (1 * scale + s*(-3 * scale + s*(3 * scale - s*scale)));
}

// Derivative of simplex noise smoothing function
// @param f = fractional distanc eto four tetrahedral corners
// @return derivative of smoothing function for each corner by x, y and z
float3x4 SimplexDSmooth(float4x3 f)
{
	const float scale = 1024. / 375.;	// scale factor to make noise -1..1
	float4 d = float4(math::dot(f[0], f[0]), math::dot(f[1], f[1]), math::dot(f[2], f[2]), math::dot(f[3], f[3]));
	float4 s = math::saturate(2 * d);
	s = -12 * scale + s*(24 * scale - s * 12 * scale);

	return float3x4(
		s * float4(f[0][0], f[1][0], f[2][0], f[3][0]),
		s * float4(f[0][1], f[1][1], f[2][1], f[3][1]),
		s * float4(f[0][2], f[1][2], f[2][2], f[3][2]));
}

// Simplex noise and its Jacobian derivative
// @param v = 3D noise argument
// @param bTiling = whether to repeat noise pattern
// @param RepeatSize = integer units before tiling in each dimension, must be a multiple of 3
// @return float3x3 Jacobian in J[*].xyz, vector noise in J[*].w
//     J[0].w, J[1].w, J[2].w is a Perlin-style simplex noise with vector output, e.g. (Nx, Ny, Nz)
//     J[i].x is X derivative of the i'th component of the noise so J[2].x is dNz/dx
// You can use this to compute the noise, gradient, curl, or divergence:
//   float3x4 J = JacobianSimplex_ALU(...);
//   float3 VNoise = float3(J[0].w, J[1].w, J[2].w);	// 3D noise
//   float3 Grad = J[0].xyz;							// gradient of J[0].w
//   float3 Curl = float3(J[1][2]-J[2][1], J[2][0]-J[0][2], J[0][1]-J[1][2]);
//   float Div = J[0][0]+J[1][1]+J[2][2];
// All of these are confirmed to compile out all unneeded terms.
// So Grad of X doesn't compute Y or Z components, and VNoise doesn't do any of the derivative computation.
float3x4 JacobianSimplex_ALU(float3 v, bool bTiling, float RepeatSize)
{
	int3 MGradientMask = int3(0x8000, 0x4000, 0x2000);
	float3 MGradientScale = float3(1. / 0x4000, 1. / 0x2000, 1. / 0x1000);

	// corners of tetrahedron
	float4x3 T = SimplexCorners(v);
	// TODO: uint3
	int3 rand = int3(0);
	float4x3 gvec0 = float4x3(1.0);
	float4x3 gvec1 = float4x3(1.0);
	float4x3 gvec2 = float4x3(1.0);
	float4x3 fv = float4x3(1.0);
	float3x4 grad = float3x4(1.0);

	// processing of tetrahedral vertices, unrolled
	// to compute gradient at each corner
	fv[0] = v - T[0];
	rand = Rand3DPCG16(int3(math::floor(NoiseTileWrap(6 * T[0] + 0.5, bTiling, RepeatSize))));
	gvec0[0] = float3(int3(rand.x,rand.x,rand.x) & MGradientMask) * MGradientScale - 1;
	gvec1[0] = float3(int3(rand.y,rand.y,rand.y) & MGradientMask) * MGradientScale - 1;
	gvec2[0] = float3(int3(rand.z,rand.z,rand.z) & MGradientMask) * MGradientScale - 1;
	grad[0][0] = math::dot(gvec0[0], fv[0]);
	grad[1][0] = math::dot(gvec1[0], fv[0]);
	grad[2][0] = math::dot(gvec2[0], fv[0]);

	fv[1] = v - T[1];
	rand = Rand3DPCG16(int3(math::floor(NoiseTileWrap(6 * T[1] + 0.5, bTiling, RepeatSize))));
	gvec0[1] = float3(int3(rand.x,rand.x,rand.x) & MGradientMask) * MGradientScale - 1;
	gvec1[1] = float3(int3(rand.y,rand.y,rand.y) & MGradientMask) * MGradientScale - 1;
	gvec1[1] = float3(int3(rand.z,rand.z,rand.z) & MGradientMask) * MGradientScale - 1;
	grad[0][1] = math::dot(gvec0[1], fv[1]);
	grad[1][1] = math::dot(gvec1[1], fv[1]);
	grad[2][1] = math::dot(gvec2[1], fv[1]);

	fv[2] = v - T[2];
	rand = Rand3DPCG16(int3(math::floor(NoiseTileWrap(6 * T[2] + 0.5, bTiling, RepeatSize))));
	gvec0[2] = float3(int3(rand.x,rand.x,rand.x) & MGradientMask) * MGradientScale - 1;
	gvec1[2] = float3(int3(rand.y,rand.y,rand.y) & MGradientMask) * MGradientScale - 1;
	gvec2[2] = float3(int3(rand.z,rand.z,rand.z) & MGradientMask) * MGradientScale - 1;
	grad[0][2] = math::dot(gvec0[2], fv[2]);
	grad[1][2] = math::dot(gvec1[2], fv[2]);
	grad[2][2] = math::dot(gvec2[2], fv[2]);

	fv[3] = v - T[3];
	rand = Rand3DPCG16(int3(math::floor(NoiseTileWrap(6 * T[3] + 0.5, bTiling, RepeatSize))));
	gvec0[3] = float3(int3(rand.x,rand.x,rand.x) & MGradientMask) * MGradientScale - 1;
	gvec1[3] = float3(int3(rand.y,rand.y,rand.y) & MGradientMask) * MGradientScale - 1;
	gvec2[3] = float3(int3(rand.z,rand.z,rand.z) & MGradientMask) * MGradientScale - 1;
	grad[0][3] = math::dot(gvec0[3], fv[3]);
	grad[1][3] = math::dot(gvec1[3], fv[3]);
	grad[2][3] = math::dot(gvec2[3], fv[3]);

	// blend gradients
	float4 sv = SimplexSmooth(fv);
	float3x4 ds = SimplexDSmooth(fv);

	float3x4 jacobian = float3x4(1.0);
	float3 vec0 = gvec0*sv + grad[0]*ds; // NOTE: mdl is column major, convert from UE4 (row major)
	jacobian[0] = float4(vec0.x, vec0.y, vec0.z, math::dot(sv, grad[0]));
	float3 vec1 = gvec1*sv + grad[1]*ds;
	jacobian[1] = float4(vec1.x, vec1.y, vec1.z, math::dot(sv, grad[1]));
	float3 vec2 = gvec2*sv + grad[2]*ds;
	jacobian[2] = float4(vec2.x, vec2.y, vec2.z, math::dot(sv, grad[2]));

	return jacobian;
}

// While RepeatSize is a float here, the expectation is that it would be largely integer values coming in from the UI. The downstream logic assumes
// floats for all called functions (NoiseTileWrap) and this prevents any float-to-int conversion errors from automatic type conversion.
float Noise3D_Multiplexer(uniform texture_2d PerlinNoiseGradientTexture, uniform texture_3d PerlinNoise3DTexture, int Function, float3 Position, int Quality, bool bTiling, float RepeatSize)
{
	// verified, HLSL compiled out the switch if Function is a constant
	switch(Function)
	{
		case 0:
			return SimplexNoise3D_TEX(PerlinNoiseGradientTexture, Position);
		case 1:
			return GradientNoise3D_TEX(PerlinNoiseGradientTexture, Position, bTiling, RepeatSize);
		case 2:
			return FastGradientPerlinNoise3D_TEX(PerlinNoise3DTexture, Position);
		case 3:
			return GradientNoise3D_ALU(Position, bTiling, RepeatSize);
		case 4:
			return ValueNoise3D_ALU(Position, bTiling, RepeatSize);
		case 5:
			return VoronoiNoise3D_ALU(Position, Quality, bTiling, RepeatSize, true).w * 2.0 - 1.0;
	}
	return 0;
}
//----------------------------------------------------------

export float noise(uniform texture_2d PerlinNoiseGradientTexture, uniform texture_3d PerlinNoise3DTexture, float3 Position, float Scale, float Quality, float Function, float Turbulence, float Levels, float OutputMin, float OutputMax, float LevelScale, float FilterWidth, float Tiling, float RepeatSize)
[[
    anno::description("Noise"),
    anno::noinline()
]]
{
	Position *= Scale;
	FilterWidth *= Scale;

	float Out = 0.0f;
	float OutScale = 1.0f;
	float InvLevelScale = 1.0f / LevelScale;
	
	int iFunction(Function);
	int iQuality(Quality);
	int iLevels(Levels);
	bool bTurbulence(Turbulence);
	bool bTiling(Tiling);
	
	for(int i = 0; i < iLevels; ++i)
	{
		// fade out noise level that are too high frequent (not done through dynamic branching as it usually requires gradient instructions)
		OutScale *= math::saturate(1.0 - FilterWidth);

		if(bTurbulence)
		{
			Out += math::abs(Noise3D_Multiplexer(PerlinNoiseGradientTexture, PerlinNoise3DTexture, iFunction, Position, iQuality, bTiling, RepeatSize)) * OutScale;
		}
		else
		{
			Out += Noise3D_Multiplexer(PerlinNoiseGradientTexture, PerlinNoise3DTexture, iFunction, Position, iQuality, bTiling, RepeatSize) * OutScale;
		}

		Position *= LevelScale;
		RepeatSize *= LevelScale;
		OutScale *= InvLevelScale;
		FilterWidth *= LevelScale;
	}

	if(!bTurbulence)
	{
		// bring -1..1 to 0..1 range
		Out = Out * 0.5f + 0.5f;
	}

	// Out is in 0..1 range
	return math::lerp(OutputMin, OutputMax, Out);
}

// Material node for noise functions returning a vector value
// @param LevelScale usually 2 but higher values allow efficient use of few levels
// @return in user defined range (OutputMin..OutputMax)
export float4 vector4_noise(float3 Position, float Quality, float Function, float Tiling, float TileSize)
[[
    anno::description("Vector Noise"),
    anno::noinline()
]]
{
	float4 result = float4(0,0,0,1);
	float3 ret = float3(0);
	int iQuality = int(Quality);
	int iFunction = int(Function);
	bool bTiling = Tiling > 0.0;
	
	float3x4 Jacobian = JacobianSimplex_ALU(Position, bTiling, TileSize);	// compiled out if not used

	// verified, HLSL compiled out the switch if Function is a constant
	switch (iFunction)
	{
	case 0:	// Cellnoise
		ret = float3(Rand3DPCG16(int3(math::floor(NoiseTileWrap(Position, bTiling, TileSize))))) / 0xffff;
		result = float4(ret.x, ret.y, ret.z, 1);
		break;
	case 1: // Color noise
		ret = float3(Jacobian[0].w, Jacobian[1].w, Jacobian[2].w);
		result = float4(ret.x, ret.y, ret.z, 1);
		break;
	case 2: // Gradient
		result = Jacobian[0];
		break;
	case 3: // Curl
		ret = float3(Jacobian[2][1] - Jacobian[1][2], Jacobian[0][2] - Jacobian[2][0], Jacobian[1][0] - Jacobian[0][1]);
		result = float4(ret.x, ret.y, ret.z, 1);
		break;
	case 4: // Voronoi
		result = VoronoiNoise3D_ALU(Position, iQuality, bTiling, TileSize, false);
		break;
	}
	return result;
}

export float3 vector3_noise(float3 Position, float Quality, float Function, float Tiling, float TileSize)
[[
    anno::description("Vector Noise float3 version"),
    anno::noinline()
]]
{
	float4 noise = vector4_noise(Position, Quality, Function, Tiling, TileSize);
	return float3(noise.x, noise.y, noise.z);
}


// workaround for ue4 fresnel (without supporting for camera vector) : replacing it with 0.0, means facing to the view
export float fresnel(float exponent [[anno::unused()]], float base_reflect_fraction [[anno::unused()]], float3 normal [[anno::unused()]])
[[
    anno::description("Fresnel"),
    anno::noinline()
]]
{
	return 0.0;
}

export float fresnel_function(float3 normal_vector [[anno::unused()]], float3 camera_vector [[anno::unused()]], 
                                bool invert_fresnel [[anno::unused()]], float power [[anno::unused()]], 
                                bool use_cheap_contrast [[anno::unused()]], float cheap_contrast_dark [[anno::unused()]], float cheap_contrast_bright [[anno::unused()]], 
                                bool clamp_fresnel_dot_product [[anno::unused()]])
[[
    anno::description("Fresnel Function"),
    anno::noinline()
]]
{
	return 0.0;
}

export float3 camera_vector(uniform bool up_z = true)
[[
    anno::description("Camera Vector"),
    anno::noinline()
]]
{
	// assume camera postion is 0,0,0
	return math::normalize(float3(0) - convert_to_left_hand(state::transform_point(state::coordinate_internal,state::coordinate_world,state::position()), up_z));
}

export float pixel_depth()
[[
    anno::description("Pixel Depth"),
    anno::noinline()
]]
{
	return 256.0f;
}

export float scene_depth()
[[
    anno::description("Scene Depth")
]]
{
	return 65500.0f;
}

export float3 scene_color()
[[
    anno::description("Scene Color")
]]
{
	return float3(1.0f);
}

export float4 vertex_color()
[[
    anno::description("Vertex Color"),
    anno::noinline()
]]
{
	return float4(1.0f);
}

export float4 vertex_color_from_coordinate(int VertexColorCoordinateIndex)
[[
    anno::description("Vertex Color for float2 PrimVar"),
    anno::noinline()
]]
{
	// Kit only supports 4 uv sets, 2 uvs are available to vertex color. if vertex color index is invalid, output the constant WHITE color intead
	return (VertexColorCoordinateIndex > 2) ? float4(1.0f) : float4(state::texture_coordinate(VertexColorCoordinateIndex).x, state::texture_coordinate(VertexColorCoordinateIndex).y, state::texture_coordinate(VertexColorCoordinateIndex+1).x, state::texture_coordinate(VertexColorCoordinateIndex+1).y);
}

export float3 camera_position()
[[
    anno::description("Camera Position"),
    anno::noinline()
]]
{
	return float3(1000.0f, 0, 0);
}

export float3 rotate_about_axis(float4 NormalizedRotationAxisAndAngle, float3 PositionOnAxis, float3 Position)
[[
    anno::description("Rotates Position about the given axis by the given angle")
]]
{
	// Project Position onto the rotation axis and find the closest point on the axis to Position
	float3 NormalizedRotationAxis = float3(NormalizedRotationAxisAndAngle.x,NormalizedRotationAxisAndAngle.y,NormalizedRotationAxisAndAngle.z);
	float3 ClosestPointOnAxis = PositionOnAxis + NormalizedRotationAxis * math::dot(NormalizedRotationAxis, Position - PositionOnAxis);
	// Construct orthogonal axes in the plane of the rotation
	float3 UAxis = Position - ClosestPointOnAxis;
	float3 VAxis = math::cross(NormalizedRotationAxis, UAxis);
	float[2] SinCosAngle = math::sincos(NormalizedRotationAxisAndAngle.w);
	// Rotate using the orthogonal axes
	float3 R = UAxis * SinCosAngle[1] + VAxis * SinCosAngle[0];
	// Reconstruct the rotated world space position
	float3 RotatedPosition = ClosestPointOnAxis + R;
	// Convert from position to a position offset
	return RotatedPosition - Position;
}

export float2 rotate_scale_offset_texcoords(float2 InTexCoords, float4 InRotationScale, float2 InOffset)
[[
    anno::description("Returns a float2 texture coordinate after 2x2 transform and offset applied")
]]
{
	return float2(math::dot(InTexCoords, float2(InRotationScale.x, InRotationScale.y)), math::dot(InTexCoords, float2(InRotationScale.z, InRotationScale.w))) + InOffset;
}

export float3 reflection_custom_world_normal(float3 WorldNormal, bool bNormalizeInputNormal, uniform bool up_z = true)
[[
    anno::description("Reflection vector about the specified world space normal")
]]
{
	if (bNormalizeInputNormal)
	{
		WorldNormal = math::normalize(WorldNormal);
	}

	return -camera_vector(up_z) + WorldNormal * math::dot(WorldNormal, camera_vector(up_z)) * 2.0;
}

export float3 reflection_vector(uniform bool up_z = true)
[[
    anno::description("Reflection Vector"),
    anno::noinline()
]]
{
    float3 normal = convert_to_left_hand(state::transform_normal(state::coordinate_internal,state::coordinate_world,state::normal()), up_z, false);
	return reflection_custom_world_normal(normal, false, up_z);
}

export float dither_temporalAA(float AlphaThreshold = 0.5f, float Random = 1.0f [[anno::unused()]])
[[
    anno::description("Dither TemporalAA"),
    anno::noinline()
]]
{
	return AlphaThreshold;
}

export float3 black_body( float Temp )
[[
    anno::description("Black Body"),
	anno::noinline()
]]
{
	float u = ( 0.860117757f + 1.54118254e-4f * Temp + 1.28641212e-7f * Temp*Temp ) / ( 1.0f + 8.42420235e-4f * Temp + 7.08145163e-7f * Temp*Temp );
	float v = ( 0.317398726f + 4.22806245e-5f * Temp + 4.20481691e-8f * Temp*Temp ) / ( 1.0f - 2.89741816e-5f * Temp + 1.61456053e-7f * Temp*Temp );

	float x = 3*u / ( 2*u - 8*v + 4 );
	float y = 2*v / ( 2*u - 8*v + 4 );
	float z = 1 - x - y;

	float Y = 1;
	float X = Y/y * x;
	float Z = Y/y * z;

	float3x3 XYZtoRGB = float3x3(
		float3(3.2404542, -1.5371385, -0.4985314),
		float3(-0.9692660,  1.8760108,  0.0415560),
		float3(0.0556434, -0.2040259,  1.0572252)
	);

	return XYZtoRGB * float3( X, Y, Z ) * math::pow( 0.0004 * Temp, 4 );
}

export float per_instance_random(uniform texture_2d PerlinNoiseGradientTexture, int NumberInstances)
[[
    anno::description("Per Instance Random"),
	anno::noinline()
]]
{
	float weight = state::object_id() / float(NumberInstances);	
	return NumberInstances == 0 ? 0.0 : tex::lookup_float4(PerlinNoiseGradientTexture, float2(weight, 1.0 - weight), tex::wrap_repeat, tex::wrap_repeat).x;
}

//------------------ Hair from UE4 -----------------------
float3 hair_absorption_to_color(float3 A)
{
	const float B = 0.3f;
	float b2 = B * B;
	float b3 = B * b2;
	float b4 = b2 * b2;
	float b5 = B * b4;
	float D = (5.969f - 0.215f * B + 2.532f * b2 - 10.73f * b3 + 5.574f * b4 + 0.245f * b5);
	return math::exp(-math::sqrt(A) * D);
}

float3 hair_color_to_absorption(float3 C)
{
	const float B = 0.3f;
	float b2 = B * B;
	float b3 = B * b2;
	float b4 = b2 * b2;
	float b5 = B * b4;
	float D = (5.969f - 0.215f * B + 2.532f * b2 - 10.73f * b3 + 5.574f * b4 + 0.245f * b5);
	return math::pow(math::log(C) / D, 2.0f);
}

export float3 get_hair_color_from_melanin(float InMelanin, float InRedness, float3 InDyeColor)
[[
    anno::description("Hair Color")
]]
{
	InMelanin = math::saturate(InMelanin);
	InRedness = math::saturate(InRedness);
	float Melanin		= -math::log(math::max(1 - InMelanin, 0.0001f));
	float Eumelanin 	= Melanin * (1 - InRedness);
	float Pheomelanin = Melanin * InRedness;

	float3 DyeAbsorption = hair_color_to_absorption(math::saturate(InDyeColor));
	float3 Absorption = Eumelanin * float3(0.506f, 0.841f, 1.653f) + Pheomelanin * float3(0.343f, 0.733f, 1.924f);

	return hair_absorption_to_color(Absorption + DyeAbsorption);
}

export float3 local_object_bounds_min()
[[
    anno::description("Local Object Bounds Min"),
	anno::noinline()
]]
{
	return float3(0.0);
}

export float3 local_object_bounds_max()
[[
    anno::description("Local Object Bounds Max"),
	anno::noinline()
]]
{
	return float3(100.0);
}

export float3 object_bounds()
[[
    anno::description("Object Bounds"),
	anno::noinline()
]]
{
	return float3(100.0);
}

export float object_radius()
[[
    anno::description("Object Radius"),
	anno::noinline()
]]
{
	return 100.0f;
}

export float3 object_world_position(uniform bool up_z = true)
[[
    anno::description("Object World Position"),
	anno::noinline()
]]
{
	return convert_to_left_hand(state::transform_point(state::coordinate_internal,state::coordinate_world,state::position()), up_z)*state::meters_per_scene_unit()*100.0;
}

export float3 object_orientation()
[[
    anno::description("Object Orientation"),
	anno::noinline()
]]
{
	return float3(0);
}

export float rcp(float x)
[[
    anno::description("hlsl rcp"),
	anno::noinline()
]]
{
	return 1.0f / x;
}

export float2 rcp(float2 x)
[[
    anno::description("hlsl rcp"),
	anno::noinline()
]]
{
	return 1.0f / x;
}

export float3 rcp(float3 x)
[[
    anno::description("hlsl rcp"),
	anno::noinline()
]]
{
	return 1.0f / x;
}

export float4 rcp(float4 x)
[[
    anno::description("hlsl rcp"),
	anno::noinline()
]]
{
	return 1.0f / x;
}

export int BitFieldExtractI32(int Data, int Size, int Offset)
[[
    anno::description("BitFieldExtractI32 int"),
	anno::noinline()
]]
{
	Size &= 3;
	Offset &= 3;

	if (Size == 0)
		return 0;
	else if (Offset + Size < 32)
		return (Data << (32 - Size - Offset)) >> (32 - Size);
	else
		return Data >> Offset;
}

export int BitFieldExtractI32(float Data, float Size, float Offset)
[[
    anno::description("BitFieldExtractI32 float"),
	anno::noinline()
]]
{
	return BitFieldExtractI32(int(Data), int(Size), int(Offset));
}

export int BitFieldExtractU32(float Data, float Size, float Offset)
[[
    anno::description("BitFieldExtractU32 float"),
	anno::noinline()
]]
{
	return BitFieldExtractI32(Data, Size, Offset);
}

export int BitFieldExtractU32(int Data, int Size, int Offset)
[[
    anno::description("BitFieldExtractU32 int"),
	anno::noinline()
]]
{
	return BitFieldExtractI32(Data, Size, Offset);
}

export float3 EyeAdaptationInverseLookup(float3 LightValue, float Alpha)
[[
    anno::description("EyeAdaptationInverseLookup"),
	anno::noinline()
]]
{
	float Adaptation = 1.0f;

	// When Alpha=0.0, we want to multiply by 1.0. when Alpha = 1.0, we want to multiply by 1/Adaptation.
	// So the lerped value is:
	//     LerpLogScale = Lerp(log(1),log(1/Adaptaiton),T)
	// Which is simplified as:
	//     LerpLogScale = Lerp(0,-log(Adaptation),T)
	//     LerpLogScale = -T * logAdaptation;

	float LerpLogScale = -Alpha * math::log(Adaptation);
	float Scale = math::exp(LerpLogScale);
	return LightValue * Scale;
}