3025b6d299
Extremely long frames caused by suspending and resuming the machine could result in an overflow in the delta smoothing because it uses 32 bit math on delta values measured in nanoseconds. This PR puts a cap of a second as the maximum frame delta that will be processed by the smoothing, otherwise it returns the frame delta 64 bit value unaltered. It also converts internal math to explicitly use 64 bit integers.
166 lines
6.7 KiB
C++
166 lines
6.7 KiB
C++
/*************************************************************************/
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/* main_timer_sync.h */
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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) 2007-2021 Juan Linietsky, Ariel Manzur. */
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/* Copyright (c) 2014-2021 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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#ifndef MAIN_TIMER_SYNC_H
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#define MAIN_TIMER_SYNC_H
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#include "core/engine.h"
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// define these to get more debugging logs for the delta smoothing
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//#define GODOT_DEBUG_DELTA_SMOOTHER
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struct MainFrameTime {
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float idle_step; // time to advance idles for (argument to process())
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int physics_steps; // number of times to iterate the physics engine
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float interpolation_fraction; // fraction through the current physics tick
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void clamp_idle(float min_idle_step, float max_idle_step);
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};
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class MainTimerSync {
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class DeltaSmoother {
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public:
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// pass the recorded delta, returns a smoothed delta
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int64_t smooth_delta(int64_t p_delta);
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private:
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void update_refresh_rate_estimator(int64_t p_delta);
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bool fps_allows_smoothing(int64_t p_delta);
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// estimated vsync delta (monitor refresh rate)
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int64_t _vsync_delta = 16666;
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// keep track of accumulated time so we know how many vsyncs to advance by
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int64_t _leftover_time = 0;
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// keep a rough measurement of the FPS as we run.
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// If this drifts a long way below or above the refresh rate, the machine
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// is struggling to keep up, and we can switch off smoothing. This
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// also deals with the case that the user has overridden the vsync in the GPU settings,
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// in which case we don't want to try smoothing.
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static const int MEASURE_FPS_OVER_NUM_FRAMES = 64;
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int64_t _measurement_time = 0;
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int64_t _measurement_frame_count = 0;
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int64_t _measurement_end_frame = MEASURE_FPS_OVER_NUM_FRAMES;
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int64_t _measurement_start_time = 0;
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bool _measurement_allows_smoothing = true;
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// we can estimate the fps by growing it on condition
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// that a large proportion of frames are higher than the current estimate.
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int32_t _estimated_fps = 0;
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int32_t _hits_at_estimated = 0;
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int32_t _hits_above_estimated = 0;
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int32_t _hits_below_estimated = 0;
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int32_t _hits_one_above_estimated = 0;
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int32_t _hits_one_below_estimated = 0;
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bool _estimate_complete = false;
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bool _estimate_locked = false;
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// data for averaging the delta over a second or so
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// to prevent spurious values
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int64_t _estimator_total_delta = 0;
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int32_t _estimator_delta_readings = 0;
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void made_new_estimate() {
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_hits_above_estimated = 0;
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_hits_at_estimated = 0;
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_hits_below_estimated = 0;
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_hits_one_above_estimated = 0;
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_hits_one_below_estimated = 0;
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_estimate_complete = false;
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#ifdef GODOT_DEBUG_DELTA_SMOOTHER
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print_line("estimated fps " + itos(_estimated_fps));
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#endif
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}
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} _delta_smoother;
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// wall clock time measured on the main thread
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uint64_t last_cpu_ticks_usec;
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uint64_t current_cpu_ticks_usec;
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// logical game time since last physics timestep
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float time_accum;
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// current difference between wall clock time and reported sum of idle_steps
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float time_deficit;
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// number of frames back for keeping accumulated physics steps roughly constant.
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// value of 12 chosen because that is what is required to make 144 Hz monitors
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// behave well with 60 Hz physics updates. The only worse commonly available refresh
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// would be 85, requiring CONTROL_STEPS = 17.
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static const int CONTROL_STEPS = 12;
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// sum of physics steps done over the last (i+1) frames
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int accumulated_physics_steps[CONTROL_STEPS];
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// typical value for accumulated_physics_steps[i] is either this or this plus one
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int typical_physics_steps[CONTROL_STEPS];
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int fixed_fps;
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protected:
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// returns the fraction of p_frame_slice 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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float get_physics_jitter_fix();
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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 get_average_physics_steps(float &p_min, float &p_max);
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// advance physics clock by p_idle_step, return appropriate number of steps to simulate
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MainFrameTime advance_core(float p_frame_slice, int p_iterations_per_second, float p_idle_step);
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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 advance_checked(float p_frame_slice, int p_iterations_per_second, float p_idle_step);
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// determine wall clock step since last iteration
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float get_cpu_idle_step();
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public:
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MainTimerSync();
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// start the clock
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void init(uint64_t p_cpu_ticks_usec);
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// set measured wall clock time
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void set_cpu_ticks_usec(uint64_t p_cpu_ticks_usec);
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//set fixed fps
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void set_fixed_fps(int p_fixed_fps);
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// advance one frame, return timesteps to take
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MainFrameTime advance(float p_frame_slice, int p_iterations_per_second);
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};
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#endif // MAIN_TIMER_SYNC_H
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