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Diffstat (limited to 'main/timer_sync.h')
| -rw-r--r-- | main/timer_sync.h | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/main/timer_sync.h b/main/timer_sync.h new file mode 100644 index 0000000000..75fbe6a9dc --- /dev/null +++ b/main/timer_sync.h @@ -0,0 +1,101 @@ +/*************************************************************************/ +/* timer_sync.h */ +/*************************************************************************/ +/* This file is part of: */ +/* GODOT ENGINE */ +/* https://godotengine.org */ +/*************************************************************************/ +/* Copyright (c) 2007-2018 Juan Linietsky, Ariel Manzur. */ +/* Copyright (c) 2014-2018 Godot Engine contributors (cf. AUTHORS.md) */ +/* */ +/* 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. */ +/*************************************************************************/ + +#ifndef TIMER_SYNC_H +#define TIMER_SYNC_H + +#include "core/engine.h" + +struct MainFrameTime { + float idle_step; // time to advance idles for (argument to process()) + int physics_steps; // number of times to iterate the physics engine + + void clamp_idle(float min_idle_step, float max_idle_step); +}; + +class MainTimerSync { + // wall clock time measured on the main thread + uint64_t last_cpu_ticks_usec; + uint64_t current_cpu_ticks_usec; + + // logical game time since last physics timestep + float time_accum; + + // current difference between wall clock time and reported sum of idle_steps + float time_deficit; + + // 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; + +protected: + // returns the fraction of p_frame_slice 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 + float 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(float &p_min, float &p_max); + + // advance physics clock by p_idle_step, return appropriate number of steps to simulate + MainFrameTime advance_core(float p_frame_slice, int p_iterations_per_second, float p_idle_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(float p_frame_slice, int p_iterations_per_second, float p_idle_step); + + // determine wall clock step since last iteration + float get_cpu_idle_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(float p_frame_slice, int p_iterations_per_second); +}; + +#endif // TIMER_SYNC_H |