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d95794ec8a
As many open source projects have started doing it, we're removing the current year from the copyright notice, so that we don't need to bump it every year. It seems like only the first year of publication is technically relevant for copyright notices, and even that seems to be something that many companies stopped listing altogether (in a version controlled codebase, the commits are a much better source of date of publication than a hardcoded copyright statement). We also now list Godot Engine contributors first as we're collectively the current maintainers of the project, and we clarify that the "exclusive" copyright of the co-founders covers the timespan before opensourcing (their further contributions are included as part of Godot Engine contributors). Also fixed "cf." Frenchism - it's meant as "refer to / see".
269 lines
10 KiB
C++
269 lines
10 KiB
C++
/**************************************************************************/
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/* main_timer_sync.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) 2014-present Godot Engine contributors (see AUTHORS.md). */
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/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
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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 "main_timer_sync.h"
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void MainFrameTime::clamp_process_step(double min_process_step, double max_process_step) {
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if (process_step < min_process_step) {
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process_step = min_process_step;
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} else if (process_step > max_process_step) {
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process_step = max_process_step;
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}
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}
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/////////////////////////////////
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// returns the fraction of p_physics_step required for the timer to overshoot
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// before advance_core considers changing the physics_steps return from
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// the typical values as defined by typical_physics_steps
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double MainTimerSync::get_physics_jitter_fix() {
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return Engine::get_singleton()->get_physics_jitter_fix();
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}
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// gets our best bet for the average number of physics steps per render frame
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// return value: number of frames back this data is consistent
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int MainTimerSync::get_average_physics_steps(double &p_min, double &p_max) {
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p_min = typical_physics_steps[0];
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p_max = p_min + 1;
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for (int i = 1; i < CONTROL_STEPS; ++i) {
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const double typical_lower = typical_physics_steps[i];
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const double current_min = typical_lower / (i + 1);
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if (current_min > p_max) {
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return i; // bail out if further restrictions would void the interval
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} else if (current_min > p_min) {
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p_min = current_min;
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}
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const double current_max = (typical_lower + 1) / (i + 1);
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if (current_max < p_min) {
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return i;
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} else if (current_max < p_max) {
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p_max = current_max;
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}
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}
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return CONTROL_STEPS;
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}
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// advance physics clock by p_process_step, return appropriate number of steps to simulate
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MainFrameTime MainTimerSync::advance_core(double p_physics_step, int p_physics_ticks_per_second, double p_process_step) {
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MainFrameTime ret;
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ret.process_step = p_process_step;
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// simple determination of number of physics iteration
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time_accum += ret.process_step;
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ret.physics_steps = floor(time_accum * p_physics_ticks_per_second);
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int min_typical_steps = typical_physics_steps[0];
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int max_typical_steps = min_typical_steps + 1;
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// given the past recorded steps and typical steps to match, calculate bounds for this
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// step to be typical
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bool update_typical = false;
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for (int i = 0; i < CONTROL_STEPS - 1; ++i) {
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int steps_left_to_match_typical = typical_physics_steps[i + 1] - accumulated_physics_steps[i];
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if (steps_left_to_match_typical > max_typical_steps ||
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steps_left_to_match_typical + 1 < min_typical_steps) {
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update_typical = true;
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break;
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}
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if (steps_left_to_match_typical > min_typical_steps) {
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min_typical_steps = steps_left_to_match_typical;
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}
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if (steps_left_to_match_typical + 1 < max_typical_steps) {
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max_typical_steps = steps_left_to_match_typical + 1;
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}
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}
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#ifdef DEBUG_ENABLED
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if (max_typical_steps < 0) {
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WARN_PRINT_ONCE("`max_typical_steps` is negative. This could hint at an engine bug or system timer misconfiguration.");
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}
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#endif
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// try to keep it consistent with previous iterations
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if (ret.physics_steps < min_typical_steps) {
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const int max_possible_steps = floor((time_accum)*p_physics_ticks_per_second + get_physics_jitter_fix());
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if (max_possible_steps < min_typical_steps) {
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ret.physics_steps = max_possible_steps;
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update_typical = true;
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} else {
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ret.physics_steps = min_typical_steps;
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}
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} else if (ret.physics_steps > max_typical_steps) {
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const int min_possible_steps = floor((time_accum)*p_physics_ticks_per_second - get_physics_jitter_fix());
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if (min_possible_steps > max_typical_steps) {
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ret.physics_steps = min_possible_steps;
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update_typical = true;
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} else {
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ret.physics_steps = max_typical_steps;
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}
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}
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if (ret.physics_steps < 0) {
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ret.physics_steps = 0;
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}
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time_accum -= ret.physics_steps * p_physics_step;
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// keep track of accumulated step counts
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for (int i = CONTROL_STEPS - 2; i >= 0; --i) {
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accumulated_physics_steps[i + 1] = accumulated_physics_steps[i] + ret.physics_steps;
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}
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accumulated_physics_steps[0] = ret.physics_steps;
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if (update_typical) {
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for (int i = CONTROL_STEPS - 1; i >= 0; --i) {
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if (typical_physics_steps[i] > accumulated_physics_steps[i]) {
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typical_physics_steps[i] = accumulated_physics_steps[i];
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} else if (typical_physics_steps[i] < accumulated_physics_steps[i] - 1) {
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typical_physics_steps[i] = accumulated_physics_steps[i] - 1;
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}
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}
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}
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return ret;
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}
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// calls advance_core, keeps track of deficit it adds to animaption_step, make sure the deficit sum stays close to zero
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MainFrameTime MainTimerSync::advance_checked(double p_physics_step, int p_physics_ticks_per_second, double p_process_step) {
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if (fixed_fps != -1) {
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p_process_step = 1.0 / fixed_fps;
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}
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float min_output_step = p_process_step / 8;
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min_output_step = MAX(min_output_step, 1E-6);
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// compensate for last deficit
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p_process_step += time_deficit;
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MainFrameTime ret = advance_core(p_physics_step, p_physics_ticks_per_second, p_process_step);
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// we will do some clamping on ret.process_step and need to sync those changes to time_accum,
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// that's easiest if we just remember their fixed difference now
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const double process_minus_accum = ret.process_step - time_accum;
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// first, least important clamping: keep ret.process_step consistent with typical_physics_steps.
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// this smoothes out the process steps and culls small but quick variations.
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{
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double min_average_physics_steps, max_average_physics_steps;
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int consistent_steps = get_average_physics_steps(min_average_physics_steps, max_average_physics_steps);
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if (consistent_steps > 3) {
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ret.clamp_process_step(min_average_physics_steps * p_physics_step, max_average_physics_steps * p_physics_step);
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}
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}
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// second clamping: keep abs(time_deficit) < jitter_fix * frame_slise
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double max_clock_deviation = get_physics_jitter_fix() * p_physics_step;
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ret.clamp_process_step(p_process_step - max_clock_deviation, p_process_step + max_clock_deviation);
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// last clamping: make sure time_accum is between 0 and p_physics_step for consistency between physics and process
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ret.clamp_process_step(process_minus_accum, process_minus_accum + p_physics_step);
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// all the operations above may have turned ret.p_process_step negative or zero, keep a minimal value
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if (ret.process_step < min_output_step) {
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ret.process_step = min_output_step;
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}
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// restore time_accum
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time_accum = ret.process_step - process_minus_accum;
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// forcing ret.process_step to be positive may trigger a violation of the
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// promise that time_accum is between 0 and p_physics_step
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#ifdef DEBUG_ENABLED
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if (time_accum < -1E-7) {
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WARN_PRINT_ONCE("Intermediate value of `time_accum` is negative. This could hint at an engine bug or system timer misconfiguration.");
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}
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#endif
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if (time_accum > p_physics_step) {
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const int extra_physics_steps = floor(time_accum * p_physics_ticks_per_second);
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time_accum -= extra_physics_steps * p_physics_step;
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ret.physics_steps += extra_physics_steps;
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}
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#ifdef DEBUG_ENABLED
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if (time_accum < -1E-7) {
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WARN_PRINT_ONCE("Final value of `time_accum` is negative. It should always be between 0 and `p_physics_step`. This hints at an engine bug.");
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}
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if (time_accum > p_physics_step + 1E-7) {
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WARN_PRINT_ONCE("Final value of `time_accum` is larger than `p_physics_step`. It should always be between 0 and `p_physics_step`. This hints at an engine bug.");
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}
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#endif
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// track deficit
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time_deficit = p_process_step - ret.process_step;
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// p_physics_step is 1.0 / iterations_per_sec
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// i.e. the time in seconds taken by a physics tick
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ret.interpolation_fraction = time_accum / p_physics_step;
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return ret;
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}
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// determine wall clock step since last iteration
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double MainTimerSync::get_cpu_process_step() {
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uint64_t cpu_ticks_elapsed = current_cpu_ticks_usec - last_cpu_ticks_usec;
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last_cpu_ticks_usec = current_cpu_ticks_usec;
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return cpu_ticks_elapsed / 1000000.0;
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}
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MainTimerSync::MainTimerSync() {
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for (int i = CONTROL_STEPS - 1; i >= 0; --i) {
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typical_physics_steps[i] = i;
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accumulated_physics_steps[i] = i;
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}
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}
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// start the clock
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void MainTimerSync::init(uint64_t p_cpu_ticks_usec) {
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current_cpu_ticks_usec = last_cpu_ticks_usec = p_cpu_ticks_usec;
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}
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// set measured wall clock time
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void MainTimerSync::set_cpu_ticks_usec(uint64_t p_cpu_ticks_usec) {
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current_cpu_ticks_usec = p_cpu_ticks_usec;
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}
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void MainTimerSync::set_fixed_fps(int p_fixed_fps) {
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fixed_fps = p_fixed_fps;
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}
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// advance one physics frame, return timesteps to take
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MainFrameTime MainTimerSync::advance(double p_physics_step, int p_physics_ticks_per_second) {
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double cpu_process_step = get_cpu_process_step();
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return advance_checked(p_physics_step, p_physics_ticks_per_second, cpu_process_step);
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}
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