godot/main/main_timer_sync.cpp

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/**************************************************************************/
/* main_timer_sync.cpp */
/**************************************************************************/
/* This file is part of: */
/* GODOT ENGINE */
/* https://godotengine.org */
/**************************************************************************/
/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
/* */
/* Permission is hereby granted, free of charge, to any person obtaining */
/* a copy of this software and associated documentation files (the */
/* "Software"), to deal in the Software without restriction, including */
/* without limitation the rights to use, copy, modify, merge, publish, */
/* distribute, sublicense, and/or sell copies of the Software, and to */
/* permit persons to whom the Software is furnished to do so, subject to */
/* the following conditions: */
/* */
/* The above copyright notice and this permission notice shall be */
/* included in all copies or substantial portions of the Software. */
/* */
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
/**************************************************************************/
2018-05-17 01:19:33 +08:00
#include "main_timer_sync.h"
#include "core/os/os.h"
#include "servers/display_server.h"
void MainFrameTime::clamp_process_step(double min_process_step, double max_process_step) {
if (process_step < min_process_step) {
process_step = min_process_step;
} else if (process_step > max_process_step) {
process_step = max_process_step;
}
}
/////////////////////////////////
void MainTimerSync::DeltaSmoother::update_refresh_rate_estimator(int64_t p_delta) {
// the calling code should prevent 0 or negative values of delta
// (preventing divide by zero)
// note that if the estimate gets locked, and something external changes this
// (e.g. user changes to non-vsync in the OS), then the results may be less than ideal,
// but usually it will detect this via the FPS measurement and not attempt smoothing.
// This should be a rare occurrence anyway, and will be cured next time user restarts game.
if (_estimate_locked) {
return;
}
// First average the delta over NUM_READINGS
_estimator_total_delta += p_delta;
_estimator_delta_readings++;
const int NUM_READINGS = 60;
if (_estimator_delta_readings < NUM_READINGS) {
return;
}
// use average
p_delta = _estimator_total_delta / NUM_READINGS;
// reset the averager for next time
_estimator_delta_readings = 0;
_estimator_total_delta = 0;
///////////////////////////////
int fps = Math::round(1000000.0 / p_delta);
// initial estimation, to speed up converging, special case we will estimate the refresh rate
// from the first average FPS reading
if (_estimated_fps == 0) {
// below 50 might be chugging loading stuff, or else
// dropping loads of frames, so the estimate will be inaccurate
if (fps >= 50) {
_estimated_fps = fps;
#ifdef GODOT_DEBUG_DELTA_SMOOTHER
print_line("initial guess (average measured) refresh rate: " + itos(fps));
#endif
} else {
// can't get started until above 50
return;
}
}
// we hit our exact estimated refresh rate.
// increase our confidence in the estimate.
if (fps == _estimated_fps) {
// note that each hit is an average of NUM_READINGS frames
_hits_at_estimated++;
if (_estimate_complete && _hits_at_estimated == 20) {
_estimate_locked = true;
#ifdef GODOT_DEBUG_DELTA_SMOOTHER
print_line("estimate LOCKED at " + itos(_estimated_fps) + " fps");
#endif
return;
}
// if we are getting pretty confident in this estimate, decide it is complete
// (it can still be increased later, and possibly lowered but only for a short time)
if ((!_estimate_complete) && (_hits_at_estimated > 2)) {
// when the estimate is complete we turn on smoothing
if (_estimated_fps) {
_estimate_complete = true;
_vsync_delta = 1000000 / _estimated_fps;
#ifdef GODOT_DEBUG_DELTA_SMOOTHER
print_line("estimate complete. vsync_delta " + itos(_vsync_delta) + ", fps " + itos(_estimated_fps));
#endif
}
}
#ifdef GODOT_DEBUG_DELTA_SMOOTHER
if ((_hits_at_estimated % (400 / NUM_READINGS)) == 0) {
String sz = "hits at estimated : " + itos(_hits_at_estimated) + ", above : " + itos(_hits_above_estimated) + "( " + itos(_hits_one_above_estimated) + " ), below : " + itos(_hits_below_estimated) + " (" + itos(_hits_one_below_estimated) + " )";
print_line(sz);
}
#endif
return;
}
const int SIGNIFICANCE_UP = 1;
const int SIGNIFICANCE_DOWN = 2;
// we are not usually interested in slowing the estimate
// but we may have overshot, so make it possible to reduce
if (fps < _estimated_fps) {
// micro changes
if (fps == (_estimated_fps - 1)) {
_hits_one_below_estimated++;
if ((_hits_one_below_estimated > _hits_at_estimated) && (_hits_one_below_estimated > SIGNIFICANCE_DOWN)) {
_estimated_fps--;
made_new_estimate();
}
return;
} else {
_hits_below_estimated++;
// don't allow large lowering if we are established at a refresh rate, as it will probably be dropped frames
bool established = _estimate_complete && (_hits_at_estimated > 10);
// macro changes
// note there is a large barrier to macro lowering. That is because it is more likely to be dropped frames
// than mis-estimation of the refresh rate.
if (!established) {
if (((_hits_below_estimated / 8) > _hits_at_estimated) && (_hits_below_estimated > SIGNIFICANCE_DOWN)) {
// decrease the estimate
_estimated_fps--;
made_new_estimate();
}
}
return;
}
}
// Changes increasing the estimate.
// micro changes
if (fps == (_estimated_fps + 1)) {
_hits_one_above_estimated++;
if ((_hits_one_above_estimated > _hits_at_estimated) && (_hits_one_above_estimated > SIGNIFICANCE_UP)) {
_estimated_fps++;
made_new_estimate();
}
return;
} else {
_hits_above_estimated++;
// macro changes
if ((_hits_above_estimated > _hits_at_estimated) && (_hits_above_estimated > SIGNIFICANCE_UP)) {
// increase the estimate
int change = fps - _estimated_fps;
change /= 2;
change = MAX(1, change);
_estimated_fps += change;
made_new_estimate();
}
return;
}
}
bool MainTimerSync::DeltaSmoother::fps_allows_smoothing(int64_t p_delta) {
_measurement_time += p_delta;
_measurement_frame_count++;
if (_measurement_frame_count == _measurement_end_frame) {
// only switch on or off if the estimate is complete
if (_estimate_complete) {
int64_t time_passed = _measurement_time - _measurement_start_time;
// average delta
time_passed /= MEASURE_FPS_OVER_NUM_FRAMES;
// estimate fps
if (time_passed) {
double fps = 1000000.0 / time_passed;
double ratio = fps / (double)_estimated_fps;
//print_line("ratio : " + String(Variant(ratio)));
if ((ratio > 0.95) && (ratio < 1.05)) {
_measurement_allows_smoothing = true;
} else {
_measurement_allows_smoothing = false;
}
}
} // estimate complete
// new start time for next iteration
_measurement_start_time = _measurement_time;
_measurement_end_frame += MEASURE_FPS_OVER_NUM_FRAMES;
}
return _measurement_allows_smoothing;
}
int64_t MainTimerSync::DeltaSmoother::smooth_delta(int64_t p_delta) {
// Conditions to disable smoothing.
// Note that vsync is a request, it cannot be relied on, the OS may override this.
// If the OS turns vsync on without vsync in the app, smoothing will not be enabled.
// If the OS turns vsync off with sync enabled in the app, the smoothing must detect this
// via the error metric and switch off.
// Also only try smoothing if vsync is enabled (classical vsync, not new types) ..
// This condition is currently checked before calling smooth_delta().
if (!OS::get_singleton()->is_delta_smoothing_enabled() || Engine::get_singleton()->is_editor_hint()) {
return p_delta;
}
// only attempt smoothing if vsync is selected
DisplayServer::VSyncMode vsync_mode = DisplayServer::get_singleton()->window_get_vsync_mode(DisplayServer::MAIN_WINDOW_ID);
if (vsync_mode != DisplayServer::VSYNC_ENABLED) {
return p_delta;
}
// Very important, ignore long deltas and pass them back unmodified.
// This is to deal with resuming after suspend for long periods.
if (p_delta > 1000000) {
return p_delta;
}
// keep a running guesstimate of the FPS, and turn off smoothing if
// conditions not close to the estimated FPS
if (!fps_allows_smoothing(p_delta)) {
return p_delta;
}
// we can't cope with negative deltas .. OS bug on some hardware
// and also very small deltas caused by vsync being off.
// This could possibly be part of a hiccup, this value isn't fixed in stone...
if (p_delta < 1000) {
return p_delta;
}
// note still some vsync off will still get through to this point...
// and we need to cope with it by not converging the estimator / and / or not smoothing
update_refresh_rate_estimator(p_delta);
// no smoothing until we know what the refresh rate is
if (!_estimate_complete) {
return p_delta;
}
// accumulate the time we have available to use
_leftover_time += p_delta;
// how many vsyncs units can we fit?
int64_t units = _leftover_time / _vsync_delta;
// a delta must include minimum 1 vsync
// (if it is less than that, it is either random error or we are no longer running at the vsync rate,
// in which case we should switch off delta smoothing, or re-estimate the refresh rate)
units = MAX(units, 1);
_leftover_time -= units * _vsync_delta;
// print_line("units " + itos(units) + ", leftover " + itos(_leftover_time/1000) + " ms");
return units * _vsync_delta;
}
/////////////////////////////////////
// returns the fraction of p_physics_step required for the timer to overshoot
// before advance_core considers changing the physics_steps return from
// the typical values as defined by typical_physics_steps
double MainTimerSync::get_physics_jitter_fix() {
// Turn off jitter fix when using fixed timestep interpolation.
// Note this shouldn't be on UNTIL 3d interpolation is implemented,
// otherwise we will get people making 3d games with the physics_interpolation
// set to on getting jitter fix disabled unexpectedly.
#if 0
if (Engine::get_singleton()->is_physics_interpolation_enabled()) {
// Would be better to write a simple bypass for jitter fix but this will do to get started.
return 0.0;
}
#endif
return Engine::get_singleton()->get_physics_jitter_fix();
}
// gets our best bet for the average number of physics steps per render frame
// return value: number of frames back this data is consistent
int MainTimerSync::get_average_physics_steps(double &p_min, double &p_max) {
p_min = typical_physics_steps[0];
p_max = p_min + 1;
for (int i = 1; i < CONTROL_STEPS; ++i) {
const double typical_lower = typical_physics_steps[i];
const double current_min = typical_lower / (i + 1);
if (current_min > p_max) {
return i; // bail out if further restrictions would void the interval
} else if (current_min > p_min) {
p_min = current_min;
}
const double current_max = (typical_lower + 1) / (i + 1);
if (current_max < p_min) {
return i;
} else if (current_max < p_max) {
p_max = current_max;
}
}
return CONTROL_STEPS;
}
// advance physics clock by p_process_step, return appropriate number of steps to simulate
MainFrameTime MainTimerSync::advance_core(double p_physics_step, int p_physics_ticks_per_second, double p_process_step) {
MainFrameTime ret;
ret.process_step = p_process_step;
// simple determination of number of physics iteration
time_accum += ret.process_step;
ret.physics_steps = floor(time_accum * p_physics_ticks_per_second);
int min_typical_steps = typical_physics_steps[0];
int max_typical_steps = min_typical_steps + 1;
// given the past recorded steps and typical steps to match, calculate bounds for this
// step to be typical
bool update_typical = false;
for (int i = 0; i < CONTROL_STEPS - 1; ++i) {
int steps_left_to_match_typical = typical_physics_steps[i + 1] - accumulated_physics_steps[i];
if (steps_left_to_match_typical > max_typical_steps ||
steps_left_to_match_typical + 1 < min_typical_steps) {
update_typical = true;
break;
}
if (steps_left_to_match_typical > min_typical_steps) {
min_typical_steps = steps_left_to_match_typical;
}
if (steps_left_to_match_typical + 1 < max_typical_steps) {
max_typical_steps = steps_left_to_match_typical + 1;
}
}
#ifdef DEBUG_ENABLED
if (max_typical_steps < 0) {
WARN_PRINT_ONCE("`max_typical_steps` is negative. This could hint at an engine bug or system timer misconfiguration.");
}
#endif
// try to keep it consistent with previous iterations
if (ret.physics_steps < min_typical_steps) {
const int max_possible_steps = floor((time_accum)*p_physics_ticks_per_second + get_physics_jitter_fix());
if (max_possible_steps < min_typical_steps) {
ret.physics_steps = max_possible_steps;
update_typical = true;
} else {
ret.physics_steps = min_typical_steps;
}
} else if (ret.physics_steps > max_typical_steps) {
const int min_possible_steps = floor((time_accum)*p_physics_ticks_per_second - get_physics_jitter_fix());
if (min_possible_steps > max_typical_steps) {
ret.physics_steps = min_possible_steps;
update_typical = true;
} else {
ret.physics_steps = max_typical_steps;
}
}
if (ret.physics_steps < 0) {
ret.physics_steps = 0;
}
time_accum -= ret.physics_steps * p_physics_step;
// keep track of accumulated step counts
for (int i = CONTROL_STEPS - 2; i >= 0; --i) {
accumulated_physics_steps[i + 1] = accumulated_physics_steps[i] + ret.physics_steps;
}
accumulated_physics_steps[0] = ret.physics_steps;
if (update_typical) {
for (int i = CONTROL_STEPS - 1; i >= 0; --i) {
if (typical_physics_steps[i] > accumulated_physics_steps[i]) {
typical_physics_steps[i] = accumulated_physics_steps[i];
} else if (typical_physics_steps[i] < accumulated_physics_steps[i] - 1) {
typical_physics_steps[i] = accumulated_physics_steps[i] - 1;
}
}
}
return ret;
}
// calls advance_core, keeps track of deficit it adds to animaption_step, make sure the deficit sum stays close to zero
MainFrameTime MainTimerSync::advance_checked(double p_physics_step, int p_physics_ticks_per_second, double p_process_step) {
if (fixed_fps != -1) {
p_process_step = 1.0 / fixed_fps;
}
float min_output_step = p_process_step / 8;
min_output_step = MAX(min_output_step, 1E-6);
// compensate for last deficit
p_process_step += time_deficit;
MainFrameTime ret = advance_core(p_physics_step, p_physics_ticks_per_second, p_process_step);
// we will do some clamping on ret.process_step and need to sync those changes to time_accum,
// that's easiest if we just remember their fixed difference now
const double process_minus_accum = ret.process_step - time_accum;
// first, least important clamping: keep ret.process_step consistent with typical_physics_steps.
// this smoothes out the process steps and culls small but quick variations.
{
double min_average_physics_steps, max_average_physics_steps;
int consistent_steps = get_average_physics_steps(min_average_physics_steps, max_average_physics_steps);
if (consistent_steps > 3) {
ret.clamp_process_step(min_average_physics_steps * p_physics_step, max_average_physics_steps * p_physics_step);
}
}
// second clamping: keep abs(time_deficit) < jitter_fix * frame_slise
double max_clock_deviation = get_physics_jitter_fix() * p_physics_step;
ret.clamp_process_step(p_process_step - max_clock_deviation, p_process_step + max_clock_deviation);
// last clamping: make sure time_accum is between 0 and p_physics_step for consistency between physics and process
ret.clamp_process_step(process_minus_accum, process_minus_accum + p_physics_step);
// all the operations above may have turned ret.p_process_step negative or zero, keep a minimal value
if (ret.process_step < min_output_step) {
ret.process_step = min_output_step;
}
// restore time_accum
time_accum = ret.process_step - process_minus_accum;
// forcing ret.process_step to be positive may trigger a violation of the
// promise that time_accum is between 0 and p_physics_step
#ifdef DEBUG_ENABLED
if (time_accum < -1E-7) {
WARN_PRINT_ONCE("Intermediate value of `time_accum` is negative. This could hint at an engine bug or system timer misconfiguration.");
}
#endif
if (time_accum > p_physics_step) {
const int extra_physics_steps = floor(time_accum * p_physics_ticks_per_second);
time_accum -= extra_physics_steps * p_physics_step;
ret.physics_steps += extra_physics_steps;
}
#ifdef DEBUG_ENABLED
if (time_accum < -1E-7) {
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.");
}
if (time_accum > p_physics_step + 1E-7) {
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.");
}
#endif
// track deficit
time_deficit = p_process_step - ret.process_step;
// p_physics_step is 1.0 / iterations_per_sec
// i.e. the time in seconds taken by a physics tick
ret.interpolation_fraction = time_accum / p_physics_step;
return ret;
}
// determine wall clock step since last iteration
double MainTimerSync::get_cpu_process_step() {
uint64_t cpu_ticks_elapsed = current_cpu_ticks_usec - last_cpu_ticks_usec;
last_cpu_ticks_usec = current_cpu_ticks_usec;
cpu_ticks_elapsed = _delta_smoother.smooth_delta(cpu_ticks_elapsed);
return cpu_ticks_elapsed / 1000000.0;
}
MainTimerSync::MainTimerSync() {
for (int i = CONTROL_STEPS - 1; i >= 0; --i) {
typical_physics_steps[i] = i;
accumulated_physics_steps[i] = i;
}
}
// start the clock
void MainTimerSync::init(uint64_t p_cpu_ticks_usec) {
current_cpu_ticks_usec = last_cpu_ticks_usec = p_cpu_ticks_usec;
}
// set measured wall clock time
void MainTimerSync::set_cpu_ticks_usec(uint64_t p_cpu_ticks_usec) {
current_cpu_ticks_usec = p_cpu_ticks_usec;
}
void MainTimerSync::set_fixed_fps(int p_fixed_fps) {
fixed_fps = p_fixed_fps;
}
// advance one physics frame, return timesteps to take
MainFrameTime MainTimerSync::advance(double p_physics_step, int p_physics_ticks_per_second) {
double cpu_process_step = get_cpu_process_step();
return advance_checked(p_physics_step, p_physics_ticks_per_second, cpu_process_step);
}