godot/core/math/math_funcs.cpp

/*************************************************************************/
/*  math_funcs.cpp                                                       */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2017 Juan Linietsky, Ariel Manzur.                 */
/*                                                                       */
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#include "math_funcs.h"
#include "core/os/os.h"

pcg32_random_t Math::default_pcg = {1, PCG_DEFAULT_INC_64};

#define PHI 0x9e3779b9

#if 0
static uint32_t Q[4096];
#endif

// TODO: we should eventually expose pcg.inc too
uint32_t Math::rand_from_seed(uint64_t *seed) {
	pcg32_random_t pcg = {*seed, PCG_DEFAULT_INC_64};
	uint32_t r = pcg32_random_r(&pcg);
	*seed = pcg.state;
	return r;
}

void Math::seed(uint64_t x) {
	default_pcg.state=x;
}

void Math::randomize() {

	OS::Time time = OS::get_singleton()->get_time();
	seed(OS::get_singleton()->get_ticks_usec()*(time.hour+1)*(time.min+1)*(time.sec+1)*rand()); // TODO: can be simplified.
}

uint32_t Math::rand() {
	return pcg32_random_r(&default_pcg);
}


int Math::step_decimals(double p_step) {
	static const int maxn=9;
	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
	};

	double as=Math::abs(p_step);
	for(int i=0;i<maxn;i++) {
		if (as>=sd[i]) {
			return i;
		}
	}

	return maxn;
}

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++;
	}

	return 0;
}

double Math::random(double from, double to) {
	unsigned int r = Math::rand();
	double ret = (double)r/(double)RANDOM_MAX;
	return (ret)*(to-from) + from;
}

float Math::random(float from, float to) {
	unsigned int r = Math::rand();
	float ret = (float)r/(float)RANDOM_MAX;
	return (ret)*(to-from) + from;
}