godot/main/main_timer_sync.h

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/**************************************************************************/
/* main_timer_sync.h */
/**************************************************************************/
/* 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
#ifndef MAIN_TIMER_SYNC_H
#define MAIN_TIMER_SYNC_H
#include "core/config/engine.h"
// Uncomment this define to get more debugging logs for the delta smoothing.
// #define GODOT_DEBUG_DELTA_SMOOTHER
struct MainFrameTime {
double process_step; // delta time to advance during process()
int physics_steps; // number of times to iterate the physics engine
double interpolation_fraction; // fraction through the current physics tick
void clamp_process_step(double min_process_step, double max_process_step);
};
class MainTimerSync {
class DeltaSmoother {
public:
// pass the recorded delta, returns a smoothed delta
int64_t smooth_delta(int64_t p_delta);
private:
void update_refresh_rate_estimator(int64_t p_delta);
bool fps_allows_smoothing(int64_t p_delta);
// estimated vsync delta (monitor refresh rate)
int64_t _vsync_delta = 16666;
// keep track of accumulated time so we know how many vsyncs to advance by
int64_t _leftover_time = 0;
// keep a rough measurement of the FPS as we run.
// If this drifts a long way below or above the refresh rate, the machine
// is struggling to keep up, and we can switch off smoothing. This
// also deals with the case that the user has overridden the vsync in the GPU settings,
// in which case we don't want to try smoothing.
static const int MEASURE_FPS_OVER_NUM_FRAMES = 64;
int64_t _measurement_time = 0;
int64_t _measurement_frame_count = 0;
int64_t _measurement_end_frame = MEASURE_FPS_OVER_NUM_FRAMES;
int64_t _measurement_start_time = 0;
bool _measurement_allows_smoothing = true;
// we can estimate the fps by growing it on condition
// that a large proportion of frames are higher than the current estimate.
int32_t _estimated_fps = 0;
int32_t _hits_at_estimated = 0;
int32_t _hits_above_estimated = 0;
int32_t _hits_below_estimated = 0;
int32_t _hits_one_above_estimated = 0;
int32_t _hits_one_below_estimated = 0;
bool _estimate_complete = false;
bool _estimate_locked = false;
// data for averaging the delta over a second or so
// to prevent spurious values
int64_t _estimator_total_delta = 0;
int32_t _estimator_delta_readings = 0;
void made_new_estimate() {
_hits_above_estimated = 0;
_hits_at_estimated = 0;
_hits_below_estimated = 0;
_hits_one_above_estimated = 0;
_hits_one_below_estimated = 0;
_estimate_complete = false;
#ifdef GODOT_DEBUG_DELTA_SMOOTHER
print_line("estimated fps " + itos(_estimated_fps));
#endif
}
} _delta_smoother;
// wall clock time measured on the main thread
uint64_t last_cpu_ticks_usec = 0;
uint64_t current_cpu_ticks_usec = 0;
// logical game time since last physics timestep
double time_accum = 0;
// current difference between wall clock time and reported sum of process_steps
double time_deficit = 0;
// number of frames back for keeping accumulated physics steps roughly constant.
// value of 12 chosen because that is what is required to make 144 Hz monitors
// behave well with 60 Hz physics updates. The only worse commonly available refresh
// would be 85, requiring CONTROL_STEPS = 17.
static const int CONTROL_STEPS = 12;
// sum of physics steps done over the last (i+1) frames
int accumulated_physics_steps[CONTROL_STEPS];
// typical value for accumulated_physics_steps[i] is either this or this plus one
int typical_physics_steps[CONTROL_STEPS];
int fixed_fps = 0;
protected:
// 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 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 get_average_physics_steps(double &p_min, double &p_max);
// advance physics clock by p_process_step, return appropriate number of steps to simulate
MainFrameTime advance_core(double p_physics_step, int p_physics_ticks_per_second, double p_process_step);
// calls advance_core, keeps track of deficit it adds to animaption_step, make sure the deficit sum stays close to zero
MainFrameTime advance_checked(double p_physics_step, int p_physics_ticks_per_second, double p_process_step);
// determine wall clock step since last iteration
double get_cpu_process_step();
public:
MainTimerSync();
// start the clock
void init(uint64_t p_cpu_ticks_usec);
// set measured wall clock time
void set_cpu_ticks_usec(uint64_t p_cpu_ticks_usec);
//set fixed fps
void set_fixed_fps(int p_fixed_fps);
// advance one frame, return timesteps to take
MainFrameTime advance(double p_physics_step, int p_physics_ticks_per_second);
};
#endif // MAIN_TIMER_SYNC_H