godot/core/math/math_funcs.cpp

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/*  math_funcs.cpp                                                       */
/*************************************************************************/
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/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
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#include "math_funcs.h"

#include "core/error_macros.h"

RandomPCG Math::default_rand(RandomPCG::DEFAULT_SEED, RandomPCG::DEFAULT_INC);

#define PHI 0x9e3779b9

uint32_t Math::rand_from_seed(uint64_t *seed) {
	RandomPCG rng = RandomPCG(*seed, RandomPCG::DEFAULT_INC);
	uint32_t r = rng.rand();
	*seed = rng.get_seed();
	return r;
}

void Math::seed(uint64_t x) {
	default_rand.seed(x);
}

void Math::randomize() {
	default_rand.randomize();
}

uint32_t Math::rand() {
	return default_rand.rand();
}

int Math::step_decimals(double p_step) {
	static const int maxn = 10;
	static const double sd[maxn] = {
		0.9999, // somehow compensate for floating point error
		0.09999,
		0.009999,
		0.0009999,
		0.00009999,
		0.000009999,
		0.0000009999,
		0.00000009999,
		0.000000009999,
		0.0000000009999
	};

	double abs = Math::abs(p_step);
	double decs = abs - (int)abs; // Strip away integer part
	for (int i = 0; i < maxn; i++) {
		if (decs >= sd[i]) {
			return i;
		}
	}

	return 0;
}

// Only meant for editor usage in float ranges, where a step of 0
// means that decimal digits should not be limited in String::num.
int Math::range_step_decimals(double p_step) {
	if (p_step < 0.0000000000001) {
		return 16; // Max value hardcoded in String::num
	}
	return step_decimals(p_step);
}

double Math::dectime(double p_value, double p_amount, double p_step) {
	double sgn = p_value < 0 ? -1.0 : 1.0;
	double val = Math::abs(p_value);
	val -= p_amount * p_step;
	if (val < 0.0) {
		val = 0.0;
	}
	return val * sgn;
}

double Math::ease(double p_x, double p_c) {
	if (p_x < 0) {
		p_x = 0;
	} else if (p_x > 1.0) {
		p_x = 1.0;
	}
	if (p_c > 0) {
		if (p_c < 1.0) {
			return 1.0 - Math::pow(1.0 - p_x, 1.0 / p_c);
		} else {
			return Math::pow(p_x, p_c);
		}
	} else if (p_c < 0) {
		//inout ease

		if (p_x < 0.5) {
			return Math::pow(p_x * 2.0, -p_c) * 0.5;
		} else {
			return (1.0 - Math::pow(1.0 - (p_x - 0.5) * 2.0, -p_c)) * 0.5 + 0.5;
		}
	} else {
		return 0; // no ease (raw)
	}
}

double Math::stepify(double p_value, double p_step) {
	if (p_step != 0) {
		p_value = Math::floor(p_value / p_step + 0.5) * p_step;
	}
	return p_value;
}

uint32_t Math::larger_prime(uint32_t p_val) {
	static const uint32_t primes[] = {
		5,
		13,
		23,
		47,
		97,
		193,
		389,
		769,
		1543,
		3079,
		6151,
		12289,
		24593,
		49157,
		98317,
		196613,
		393241,
		786433,
		1572869,
		3145739,
		6291469,
		12582917,
		25165843,
		50331653,
		100663319,
		201326611,
		402653189,
		805306457,
		1610612741,
		0,
	};

	int idx = 0;
	while (true) {
		ERR_FAIL_COND_V(primes[idx] == 0, 0);
		if (primes[idx] > p_val) {
			return primes[idx];
		}
		idx++;
	}
}

double Math::random(double from, double to) {
	return default_rand.random(from, to);
}

float Math::random(float from, float to) {
	return default_rand.random(from, to);
}