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5f1b9a2313
When generating single precision floats, Godot casts a uint32_t to float, causing uniformity loss. This new randf, inspired by T. R. Campbell's random_real, samples the output of rand as the fraction part of an infinite binary number, with some tricks to reduce ops and branching. This method provides "good enough" uniformity at decent speed, for floats greater than 2^-64. Smaller numbers are floored to 0.
53 lines
2.6 KiB
C++
53 lines
2.6 KiB
C++
/*************************************************************************/
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/* random_pcg.cpp */
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/*************************************************************************/
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/* This file is part of: */
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/* GODOT ENGINE */
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/* https://godotengine.org */
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/*************************************************************************/
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/* Copyright (c) 2007-2019 Juan Linietsky, Ariel Manzur. */
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/* Copyright (c) 2014-2019 Godot Engine contributors (cf. AUTHORS.md) */
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/* */
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/* Permission is hereby granted, free of charge, to any person obtaining */
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/* a copy of this software and associated documentation files (the */
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/* "Software"), to deal in the Software without restriction, including */
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/* without limitation the rights to use, copy, modify, merge, publish, */
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/* distribute, sublicense, and/or sell copies of the Software, and to */
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/* permit persons to whom the Software is furnished to do so, subject to */
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/* the following conditions: */
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/* */
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/* The above copyright notice and this permission notice shall be */
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/* included in all copies or substantial portions of the Software. */
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/* */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
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/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
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/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
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/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
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/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
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/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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/*************************************************************************/
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#include "random_pcg.h"
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#include "core/os/os.h"
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RandomPCG::RandomPCG(uint64_t p_seed, uint64_t p_inc) :
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pcg(),
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current_seed(DEFAULT_SEED) {
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pcg.inc = p_inc;
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seed(p_seed);
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}
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void RandomPCG::randomize() {
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seed(OS::get_singleton()->get_ticks_usec() * pcg.state + PCG_DEFAULT_INC_64);
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}
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double RandomPCG::random(double p_from, double p_to) {
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return randd() * (p_to - p_from) + p_from;
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}
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float RandomPCG::random(float p_from, float p_to) {
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return randf() * (p_to - p_from) + p_from;
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}
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