Files
test/intern/cycles/util/math_float3.h
Lukas Stockner eaa5f63ba2 Cycles: Replace thin-film basis function approximation with accurate LUTs
Previously, we used precomputed Gaussian fits to the XYZ CMFs, performed
the spectral integration in that space, and then converted the result
to the RGB working space.

That worked because we're only supporting dielectric base layers for
the thin film code, so the inputs to the spectral integration
(reflectivity and phase) are both constant w.r.t. wavelength.

However, this will no longer work for conductive base layers.
We could handle reflectivity by converting to XYZ, but that won't work
for phase since its effect on the output is nonlinear.

Therefore, it's time to do this properly by performing the spectral
integration directly in the RGB primaries. To do this, we need to:
- Compute the RGB CMFs from the XYZ CMFs and XYZ-to-RGB matrix
- Resample the RGB CMFs to be parametrized by frequency instead of wavelength
- Compute the FFT of the CMFs
- Store it as a LUT to be used by the kernel code

However, there's two optimizations we can make:
- Both the resampling and the FFT are linear operations, as is the
  XYZ-to-RGB conversion. Therefore, we can resample and Fourier-transform
  the XYZ CMFs once, store the result in a precomputed table, and then just
  multiply the entries by the XYZ-to-RGB matrix at runtime.
  - I've included the Python script used to compute the table under
    `intern/cycles/doc/precompute`.
- The reference implementation by the paper authors [1] simply stores the
  real and imaginary parts in the LUT, and then computes
  `cos(shift)*real + sin(shift)*imag`. However, the real and imaginary parts
  are oscillating, so the LUT with linear interpolation is not particularly
  good at representing them. Instead, we can convert the table to
  Magnitude/Phase representation, which is much smoother, and do
  `mag * cos(phase - shift)` in the kernel.
  - Phase needs to be unwrapped to handle the interpolation decently,
    but that's easy.
  - This requires an extra trig operation in the kernel in the dielectric case,
    but for the conductive case we'll actually save three.

Rendered output is mostly the same, just slightly different because we're
no longer using the Gaussian approximation.

[1] "A Practical Extension to Microfacet Theory for the Modeling of
    Varying Iridescence" by Laurent Belcour and Pascal Barla,
    https://belcour.github.io/blog/research/publication/2017/05/01/brdf-thin-film.html

Pull Request: https://projects.blender.org/blender/blender/pulls/140944
2025-07-09 22:10:28 +02:00

686 lines
17 KiB
C++

/* SPDX-FileCopyrightText: 2011-2013 Intel Corporation
* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
*
* SPDX-License-Identifier: Apache-2.0 */
#pragma once
#include "util/math_base.h"
#include "util/math_float4.h"
#include "util/types_float3.h"
#include "util/types_float4.h"
#include "util/types_int3.h"
CCL_NAMESPACE_BEGIN
ccl_device_inline float3 zero_float3()
{
#ifdef __KERNEL_SSE__
return float3(_mm_setzero_ps());
#else
return make_float3(0.0f, 0.0f, 0.0f);
#endif
}
ccl_device_inline float3 one_float3()
{
return make_float3(1.0f, 1.0f, 1.0f);
}
ccl_device_template_spec float3 make_zero()
{
return zero_float3();
}
ccl_device_inline float3 reciprocal(const float3 a)
{
#ifdef __KERNEL_SSE__
/* Don't use _mm_rcp_ps due to poor precision. */
return float3(_mm_div_ps(_mm_set_ps1(1.0f), a.m128));
#else
return make_float3(1.0f / a.x, 1.0f / a.y, 1.0f / a.z);
#endif
}
#ifndef __KERNEL_METAL__
ccl_device_inline float3 operator-(const float3 &a)
{
# ifdef __KERNEL_SSE__
return float3(_mm_xor_ps(a.m128, _mm_castsi128_ps(_mm_set1_epi32(0x80000000))));
# else
return make_float3(-a.x, -a.y, -a.z);
# endif
}
ccl_device_inline float3 operator*(const float3 a, const float3 b)
{
# ifdef __KERNEL_SSE__
return float3(_mm_mul_ps(a.m128, b.m128));
# else
return make_float3(a.x * b.x, a.y * b.y, a.z * b.z);
# endif
}
ccl_device_inline float3 operator*(const float3 a, const float f)
{
# ifdef __KERNEL_SSE__
return float3(_mm_mul_ps(a.m128, _mm_set1_ps(f)));
# else
return make_float3(a.x * f, a.y * f, a.z * f);
# endif
}
ccl_device_inline float3 operator*(const float f, const float3 a)
{
# if defined(__KERNEL_SSE__)
return float3(_mm_mul_ps(_mm_set1_ps(f), a.m128));
# else
return make_float3(a.x * f, a.y * f, a.z * f);
# endif
}
ccl_device_inline float3 operator/(const float f, const float3 a)
{
# if defined(__KERNEL_SSE__)
return float3(_mm_div_ps(_mm_set1_ps(f), a.m128));
# else
return make_float3(f / a.x, f / a.y, f / a.z);
# endif
}
ccl_device_inline float3 operator/(const float3 a, const float f)
{
# if defined(__KERNEL_SSE__)
return float3(_mm_div_ps(a.m128, _mm_set1_ps(f)));
# else
float invf = 1.0f / f;
return make_float3(a.x * invf, a.y * invf, a.z * invf);
# endif
}
ccl_device_inline float3 operator/(const float3 a, const float3 b)
{
# if defined(__KERNEL_SSE__)
return float3(_mm_div_ps(a.m128, b.m128));
# else
return make_float3(a.x / b.x, a.y / b.y, a.z / b.z);
# endif
}
ccl_device_inline float3 operator+(const float3 a, const float3 b)
{
# ifdef __KERNEL_SSE__
return float3(_mm_add_ps(a.m128, b.m128));
# else
return make_float3(a.x + b.x, a.y + b.y, a.z + b.z);
# endif
}
ccl_device_inline float3 operator+(const float3 a, const float f)
{
return a + make_float3(f);
}
ccl_device_inline float3 operator-(const float3 a, const float3 b)
{
# ifdef __KERNEL_SSE__
return float3(_mm_sub_ps(a.m128, b.m128));
# else
return make_float3(a.x - b.x, a.y - b.y, a.z - b.z);
# endif
}
ccl_device_inline float3 operator-(const float3 a, const float f)
{
return a - make_float3(f);
}
ccl_device_inline float3 operator+=(float3 &a, const float3 b)
{
return a = a + b;
}
ccl_device_inline float3 operator-=(float3 &a, const float3 b)
{
return a = a - b;
}
ccl_device_inline float3 operator*=(float3 &a, const float3 b)
{
return a = a * b;
}
ccl_device_inline float3 operator*=(float3 &a, const float f)
{
return a = a * f;
}
ccl_device_inline float3 operator/=(float3 &a, const float3 b)
{
return a = a / b;
}
ccl_device_inline float3 operator/=(float3 &a, const float f)
{
const float invf = 1.0f / f;
return a = a * invf;
}
# if !(defined(__KERNEL_CUDA__) || defined(__KERNEL_HIP__) || defined(__KERNEL_ONEAPI__))
ccl_device_inline packed_float3 operator*=(packed_float3 &a, const float3 b)
{
a = float3(a) * b;
return a;
}
ccl_device_inline packed_float3 operator*=(packed_float3 &a, const float f)
{
a = float3(a) * f;
return a;
}
ccl_device_inline packed_float3 operator/=(packed_float3 &a, const float3 b)
{
a = float3(a) / b;
return a;
}
ccl_device_inline packed_float3 operator/=(packed_float3 &a, const float f)
{
a = float3(a) / f;
return a;
}
# endif
ccl_device_inline bool operator==(const float3 a, const float3 b)
{
# ifdef __KERNEL_SSE__
return (_mm_movemask_ps(_mm_cmpeq_ps(a.m128, b.m128)) & 7) == 7;
# else
return (a.x == b.x && a.y == b.y && a.z == b.z);
# endif
}
ccl_device_inline bool operator!=(const float3 a, const float3 b)
{
return !(a == b);
}
ccl_device_inline int3 operator>=(const float3 a, const float3 b)
{
# ifdef __KERNEL_SSE__
return int3(_mm_castps_si128(_mm_cmpge_ps(a.m128, b.m128)));
# else
return make_int3(a.x >= b.x, a.y >= b.y, a.z >= b.z);
# endif
}
ccl_device_inline float dot(const float3 a, const float3 b)
{
# if defined(__KERNEL_SSE42__) && defined(__KERNEL_SSE__)
return _mm_cvtss_f32(_mm_dp_ps(a, b, 0x7F));
# else
return a.x * b.x + a.y * b.y + a.z * b.z;
# endif
}
#endif
ccl_device_inline float dot_xy(const float3 a, const float3 b)
{
#if defined(__KERNEL_SSE42__) && defined(__KERNEL_SSE__)
return _mm_cvtss_f32(_mm_hadd_ps(_mm_mul_ps(a, b), b));
#else
return a.x * b.x + a.y * b.y;
#endif
}
ccl_device_inline float len(const float3 a)
{
#if defined(__KERNEL_SSE42__) && defined(__KERNEL_SSE__)
return _mm_cvtss_f32(_mm_sqrt_ss(_mm_dp_ps(a.m128, a.m128, 0x7F)));
#else
return sqrtf(dot(a, a));
#endif
}
ccl_device_inline float reduce_min(const float3 a)
{
return min(min(a.x, a.y), a.z);
}
ccl_device_inline float reduce_max(const float3 a)
{
return max(max(a.x, a.y), a.z);
}
ccl_device_inline float len_squared(const float3 a)
{
return dot(a, a);
}
#ifndef __KERNEL_METAL__
ccl_device_inline float distance(const float3 a, const float3 b)
{
return len(a - b);
}
ccl_device_inline float3 cross(const float3 a, const float3 b)
{
# ifdef __KERNEL_SSE__
const float4 x = float4(a.m128);
const float4 y = shuffle<1, 2, 0, 3>(float4(b.m128));
const float4 z = float4(_mm_mul_ps(shuffle<1, 2, 0, 3>(float4(a.m128)), float4(b.m128)));
return float3(shuffle<1, 2, 0, 3>(msub(x, y, z)).m128);
# else
return make_float3(a.y * b.z - a.z * b.y, a.z * b.x - a.x * b.z, a.x * b.y - a.y * b.x);
# endif
}
ccl_device_inline float3 normalize(const float3 a)
{
# if defined(__KERNEL_SSE42__) && defined(__KERNEL_SSE__)
const __m128 norm = _mm_sqrt_ps(_mm_dp_ps(a.m128, a.m128, 0x7F));
return float3(_mm_div_ps(a.m128, norm));
# else
return a / len(a);
# endif
}
ccl_device_inline float3 min(const float3 a, const float3 b)
{
# ifdef __KERNEL_SSE__
return float3(_mm_min_ps(a.m128, b.m128));
# else
return make_float3(min(a.x, b.x), min(a.y, b.y), min(a.z, b.z));
# endif
}
ccl_device_inline float3 max(const float3 a, const float3 b)
{
# ifdef __KERNEL_SSE__
return float3(_mm_max_ps(a.m128, b.m128));
# else
return make_float3(max(a.x, b.x), max(a.y, b.y), max(a.z, b.z));
# endif
}
ccl_device_inline float3 clamp(const float3 a, const float3 mn, const float3 mx)
{
return min(max(a, mn), mx);
}
ccl_device_inline float3 fabs(const float3 a)
{
# ifdef __KERNEL_SSE__
# ifdef __KERNEL_NEON__
return float3(vabsq_f32(a.m128));
# else
__m128 mask = _mm_castsi128_ps(_mm_set1_epi32(0x7fffffff));
return float3(_mm_and_ps(a.m128, mask));
# endif
# else
return make_float3(fabsf(a.x), fabsf(a.y), fabsf(a.z));
# endif
}
/* The floating-point remainder of the division operation a / b calculated by this function is
* exactly the value a - iquot * b, where iquot is a / b with its fractional part truncated.
*
* The returned value has the same sign as a and is less than b in magnitude. */
ccl_device_inline float3 fmod(const float3 a, const float b)
{
# if defined(__KERNEL_NEON__)
/* Use native Neon instructions.
* The logic is the same as the SSE code below, but on Apple M2 Ultra this seems to be faster.
* Possibly due to some runtime checks in _mm_round_ps which do not get properly inlined. */
const float32x4_t iquot = vrndq_f32(a / b);
return float3(vsubq_f32(a, vmulq_f32(iquot, vdupq_n_f32(b))));
# elif defined(__KERNEL_SSE42__) && defined(__KERNEL_SSE__)
const __m128 iquot = _mm_round_ps(a / b, _MM_FROUND_TRUNC);
return float3(_mm_sub_ps(a, _mm_mul_ps(iquot, _mm_set1_ps(b))));
# else
return make_float3(fmodf(a.x, b), fmodf(a.y, b), fmodf(a.z, b));
# endif
}
ccl_device_inline float3 sqrt(const float3 a)
{
# ifdef __KERNEL_SSE__
return float3(_mm_sqrt_ps(a));
# else
return make_float3(sqrtf(a.x), sqrtf(a.y), sqrtf(a.z));
# endif
}
ccl_device_inline float3 floor(const float3 a)
{
# ifdef __KERNEL_SSE__
return float3(_mm_floor_ps(a));
# else
return make_float3(floorf(a.x), floorf(a.y), floorf(a.z));
# endif
}
ccl_device_inline float3 ceil(const float3 a)
{
# ifdef __KERNEL_SSE__
return float3(_mm_ceil_ps(a));
# else
return make_float3(ceilf(a.x), ceilf(a.y), ceilf(a.z));
# endif
}
ccl_device_inline float3 mix(const float3 a, const float3 b, const float t)
{
return a + t * (b - a);
}
ccl_device_inline float3 saturate(const float3 a)
{
return make_float3(saturatef(a.x), saturatef(a.y), saturatef(a.z));
}
ccl_device_inline float3 exp(const float3 v)
{
return make_float3(expf(v.x), expf(v.y), expf(v.z));
}
ccl_device_inline float3 log(const float3 v)
{
return make_float3(logf(v.x), logf(v.y), logf(v.z));
}
ccl_device_inline float3 cos(const float3 v)
{
return make_float3(cosf(v.x), cosf(v.y), cosf(v.z));
}
ccl_device_inline float3 atan2(const float3 y, const float3 x)
{
return make_float3(atan2f(y.x, x.x), atan2f(y.y, x.y), atan2f(y.z, x.z));
}
ccl_device_inline float3 round(const float3 a)
{
return make_float3(roundf(a.x), roundf(a.y), roundf(a.z));
}
ccl_device_inline float3 reflect(const float3 incident, const float3 unit_normal)
{
return incident - 2.0f * unit_normal * dot(incident, unit_normal);
}
ccl_device_inline float3 refract(const float3 incident, const float3 normal, const float eta)
{
const float k = 1.0f - eta * eta * (1.0f - dot(normal, incident) * dot(normal, incident));
if (k < 0.0f) {
return zero_float3();
}
return eta * incident - (eta * dot(normal, incident) + sqrt(k)) * normal;
}
ccl_device_inline float3 faceforward(const float3 vector,
const float3 incident,
const float3 reference)
{
return (dot(reference, incident) < 0.0f) ? vector : -vector;
}
#endif
ccl_device_inline float3 project(const float3 v, const float3 v_proj)
{
const float len_squared = dot(v_proj, v_proj);
return (len_squared != 0.0f) ? (dot(v, v_proj) / len_squared) * v_proj : zero_float3();
}
ccl_device_inline float3 normalize_len(const float3 a, ccl_private float *t)
{
*t = len(a);
const float x = 1.0f / *t;
return a * x;
}
ccl_device_inline float3 safe_normalize(const float3 a)
{
const float t = len(a);
return (t != 0.0f) ? a * (1.0f / t) : a;
}
ccl_device_inline float3 safe_normalize_fallback(const float3 a, const float3 fallback)
{
const float t = len(a);
return (t != 0.0f) ? a * (1.0f / t) : fallback;
}
ccl_device_inline float3 safe_normalize_len(const float3 a, ccl_private float *t)
{
*t = len(a);
return (*t != 0.0f) ? a / (*t) : a;
}
ccl_device_inline float3 safe_divide(const float3 a, const float3 b)
{
return make_float3((b.x != 0.0f) ? a.x / b.x : 0.0f,
(b.y != 0.0f) ? a.y / b.y : 0.0f,
(b.z != 0.0f) ? a.z / b.z : 0.0f);
}
ccl_device_inline float3 safe_divide(const float3 a, const float b)
{
return (b != 0.0f) ? a / b : zero_float3();
}
ccl_device_inline float3 interp(const float3 a, const float3 b, const float t)
{
return a + t * (b - a);
}
ccl_device_inline float3 sqr(const float3 a)
{
return a * a;
}
ccl_device_inline bool is_zero(const float3 a)
{
#ifdef __KERNEL_SSE__
return a == make_float3(0.0f);
#else
return (a.x == 0.0f && a.y == 0.0f && a.z == 0.0f);
#endif
}
ccl_device_inline float reduce_add(const float3 a)
{
#if defined(__KERNEL_SSE__) && defined(__KERNEL_NEON__)
__m128 t = a.m128;
t = vsetq_lane_f32(0.0f, t, 3);
return vaddvq_f32(t);
#else
return (a.x + a.y + a.z);
#endif
}
ccl_device_inline float average(const float3 a)
{
return reduce_add(a) * (1.0f / 3.0f);
}
ccl_device_inline bool isequal(const float3 a, const float3 b)
{
#if defined(__KERNEL_METAL__)
return all(a == b);
#else
return a == b;
#endif
}
template<class MaskType>
ccl_device_inline float3 select(const MaskType mask, const float3 a, const float3 b)
{
#if defined(__KERNEL_METAL__)
return metal::select(b, a, bool3(mask));
#elif defined(__KERNEL_SSE__)
# ifdef __KERNEL_SSE42__
return float3(_mm_blendv_ps(b.m128, a.m128, _mm_castsi128_ps(mask.m128)));
# else
return float4(
_mm_or_ps(_mm_and_ps(_mm_castsi128_ps(mask), a), _mm_andnot_ps(_mm_castsi128_ps(mask), b)));
# endif
#else
return make_float3((mask.x) ? a.x : b.x, (mask.y) ? a.y : b.y, (mask.z) ? a.z : b.z);
#endif
}
template<class MaskType> ccl_device_inline float3 mask(const MaskType mask, const float3 a)
{
/* Replace elements of x with zero where mask isn't set. */
return select(mask, a, zero_float3());
}
/* Consistent name for this would be pow, but HIP compiler crashes in name mangling. */
ccl_device_inline float3 power(const float3 v, const float e)
{
return make_float3(powf(v.x, e), powf(v.y, e), powf(v.z, e));
}
ccl_device_inline bool isfinite_safe(const float3 v)
{
return isfinite_safe(v.x) && isfinite_safe(v.y) && isfinite_safe(v.z);
}
ccl_device_inline float3 ensure_finite(const float3 v)
{
float3 r = v;
if (!isfinite_safe(r.x)) {
r.x = 0.0f;
}
if (!isfinite_safe(r.y)) {
r.y = 0.0f;
}
if (!isfinite_safe(r.z)) {
r.z = 0.0f;
}
return r;
}
/* Triangle */
ccl_device_inline float triangle_area(const ccl_private float3 &v1,
const ccl_private float3 &v2,
const ccl_private float3 &v3)
{
return len(cross(v3 - v2, v1 - v2)) * 0.5f;
}
/* Orthonormal vectors */
ccl_device_inline void make_orthonormals(const float3 N,
ccl_private float3 *a,
ccl_private float3 *b)
{
#if 0
if (fabsf(N.y) >= 0.999f) {
*a = make_float3(1, 0, 0);
*b = make_float3(0, 0, 1);
return;
}
if (fabsf(N.z) >= 0.999f) {
*a = make_float3(1, 0, 0);
*b = make_float3(0, 1, 0);
return;
}
#endif
if (N.x != N.y || N.x != N.z) {
*a = make_float3(N.z - N.y, N.x - N.z, N.y - N.x); //(1,1,1)x N
}
else {
*a = make_float3(N.z - N.y, N.x + N.z, -N.y - N.x); //(-1,1,1)x N
}
*a = normalize(*a);
*b = cross(N, *a);
}
/* Rotation of point around axis and angle */
ccl_device_inline float3 rotate_around_axis(const float3 p, const float3 axis, const float angle)
{
const float costheta = cosf(angle);
const float sintheta = sinf(angle);
float3 r;
r.x = ((costheta + (1 - costheta) * axis.x * axis.x) * p.x) +
(((1 - costheta) * axis.x * axis.y - axis.z * sintheta) * p.y) +
(((1 - costheta) * axis.x * axis.z + axis.y * sintheta) * p.z);
r.y = (((1 - costheta) * axis.x * axis.y + axis.z * sintheta) * p.x) +
((costheta + (1 - costheta) * axis.y * axis.y) * p.y) +
(((1 - costheta) * axis.y * axis.z - axis.x * sintheta) * p.z);
r.z = (((1 - costheta) * axis.x * axis.z - axis.y * sintheta) * p.x) +
(((1 - costheta) * axis.y * axis.z + axis.x * sintheta) * p.y) +
((costheta + (1 - costheta) * axis.z * axis.z) * p.z);
return r;
}
/* Calculate the angle between the two vectors a and b.
* The usual approach `acos(dot(a, b))` has severe precision issues for small angles,
* which are avoided by this method.
* Based on "Mangled Angles" from https://people.eecs.berkeley.edu/~wkahan/Mindless.pdf
*/
ccl_device_inline float precise_angle(const float3 a, const float3 b)
{
return 2.0f * atan2f(len(a - b), len(a + b));
}
/* Tangent of the angle between vectors a and b. */
ccl_device_inline float tan_angle(const float3 a, const float3 b)
{
return len(cross(a, b)) / dot(a, b);
}
/* projections */
ccl_device_inline float2 map_to_tube(const float3 co)
{
float len;
float u;
float v;
len = sqrtf(co.x * co.x + co.y * co.y);
if (len > 0.0f) {
u = (1.0f - (atan2f(co.x / len, co.y / len) / M_PI_F)) * 0.5f;
v = (co.z + 1.0f) * 0.5f;
}
else {
u = v = 0.0f;
}
return make_float2(u, v);
}
ccl_device_inline float2 map_to_sphere(const float3 co)
{
const float l = dot(co, co);
float u;
float v;
if (l > 0.0f) {
if (UNLIKELY(co.x == 0.0f && co.y == 0.0f)) {
u = 0.0f; /* Otherwise domain error. */
}
else {
u = (0.5f - atan2f(co.x, co.y) * M_1_2PI_F);
}
v = 1.0f - safe_acosf(co.z / sqrtf(l)) * M_1_PI_F;
}
else {
u = v = 0.0f;
}
return make_float2(u, v);
}
CCL_NAMESPACE_END