Differential D15589 Diff 55385 intern/mikktspace/mikk_util.hh

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intern/mikktspace/mikk_util.hh

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				/* SPDX-License-Identifier: Apache-2.0 */

				/** \file
				* \ingroup mikktspace
				*/

				#pragma once

				#include <cassert>
				#include <cmath>

				#ifndef M_PI_F
				# define M_PI_F (3.1415926535897932f) /* pi */
				#endif

				namespace mikk {

				inline bool not_zero(const float fX)
				{
				return fabsf(fX) > FLT_MIN;
				}

				/* Helpers for (un)packing a 2-bit vertex index and a 30-bit face index to one integer. */
				static uint pack_index(const uint face, const uint vert)
				{
				assert((vert & 0x3) == vert);
				return (face << 2) \| (vert & 0x3);
				}

				static void unpack_index(uint &face, uint &vert, const uint indexIn)
				{
				vert = indexIn & 0x3;
				face = indexIn >> 2;
				}

				/* From intern/cycles/util/math_fast.h */
				inline float fast_acosf(float x)
				{
				const float f = fabsf(x);
				/* clamp and crush denormals. */
				const float m = (f < 1.0f) ? 1.0f - (1.0f - f) : 1.0f;
				/* Based on http://www.pouet.net/topic.php?which=9132&page=2
				* 85% accurate (ulp 0)
				* Examined 2130706434 values of acos:
				* 15.2000597 avg ulp diff, 4492 max ulp, 4.51803e-05 max error // without "denormal crush"
				* Examined 2130706434 values of acos:
				* 15.2007108 avg ulp diff, 4492 max ulp, 4.51803e-05 max error // with "denormal crush"
				*/
				const float a = sqrtf(1.0f - m) *
				(1.5707963267f + m * (-0.213300989f + m * (0.077980478f + m * -0.02164095f)));
				return x < 0 ? M_PI_F - a : a;
				}

				static uint rotl(uint x, uint k)
				{
				return (x << k) \| (x >> (32 - k));
				}

				static uint hash_uint3(uint kx, uint ky, uint kz)
				{
				uint a, b, c;
				a = b = c = 0xdeadbeef + (2 << 2) + 13;

				c += kz;
				b += ky;
				a += kx;

				c = (c ^ b) - rotl(b, 14);
				a = (a ^ c) - rotl(c, 11);
				b = (b ^ a) - rotl(a, 25);
				c = (c ^ b) - rotl(b, 16);

				return c;
				}

				static uint hash_uint3_fast(const uint x, const uint y, const uint z)
				{
				return (x * 73856093) ^ (y * 19349663) ^ (z * 83492791);
				}

				static uint float_as_uint(const float v)
				{
				return ((uint )(&v));
				}

				static float uint_as_float(const uint v)
				{
				return ((float )(&v));
				}

				static uint hash_float3_fast(const float x, const float y, const float z)
				{
				return hash_uint3_fast(float_as_uint(x), float_as_uint(y), float_as_uint(z));
				}

				static uint hash_float3x3(const float3 &x, const float3 &y, const float3 &z)
				{
				return hash_uint3(hash_float3_fast(x.x, x.y, x.z),
				hash_float3_fast(y.x, y.y, y.z),
				hash_float3_fast(z.x, z.y, z.z));
				}

				template<typename T, typename KeyGetter>
				void radixsort(std::vector<T> &data, std::vector<T> &data2, KeyGetter getKey)
				{
				typedef decltype(getKey(data[0])) key_t;
				constexpr size_t datasize = sizeof(key_t);
				static_assert(datasize % 2 == 0);
				static_assert(std::is_integral<key_t>::value);

				uint bins[datasize][257] = {0};

				/* Count number of elements per bin. */
				for (const T &item : data) {
				key_t key = getKey(item);
				for (uint pass = 0; pass < datasize; pass++)
				bins[pass][((key >> (8 * pass)) & 0xff) + 1]++;
				}

				/* Compute prefix sum to find position of each bin in the sorted array. */
				for (uint pass = 0; pass < datasize; pass++) {
				for (uint i = 2; i < 256; i++) {
				bins[pass][i] += bins[pass][i - 1];
				}
				}

				int shift = 0;
				for (uint pass = 0; pass < datasize; pass++, shift += 8) {
				/* Insert the elements in their correct location based on their bin. */
				for (const T &item : data) {
				uint pos = bins[pass][(getKey(item) >> shift) & 0xff]++;
				data2[pos] = item;
				}

				/* Swap arrays. */
				std::swap(data, data2);
				}
				}

				static void float_add_atomic(float *val, float add)
				{
				/* Hacky, but atomic floats are only supported from C++20 onwards.
				* This works in practise since std::atomic<uint32_t> is really just an uint32_t in memory,
				* so this cast lets us do a 32-bit CAS operation (which is used to build the atomic float
				* operation) without needing any external libraries or compiler-specific builtins. */
				std::atomic<uint32_t> atomic_val = reinterpret_cast<std::atomic<uint32_t> >(val);
				for (;;) {
				uint32_t old_v = atomic_val->load();
				uint32_t new_v = float_as_uint(uint_as_float(old_v) + add);
				if (atomic_val->compare_exchange_weak(old_v, new_v)) {
				return;
				}
				}
				}

				} // namespace mikk