Add new class _TimerSync to manage timestep calculations. The new class handles the decisions about simulation progression previously handled by main::iteration(). It is fed the current timer ticks and determines how many physics updates are to be run and what the delta argument to the _process() functions should be. The new class tries to keep the number of physics updates per frame as constant as possible from frame to frame. Ideally, it would be N steps every render frame, but even with perfectly regular rendering, the general case is that N or N+1 steps are required per frame, for some fixed N. The best guess for N is stored in typical_physics_steps. When determining the number of steps to take, no restrictions are imposed between the choice of typical_physics_steps and typical_physics_steps+1 steps. Should more or less steps than that be required, the accumulated remaining time (as before, stored in time_accum) needs to surpass its boundaries by some minimal threshold. Once surpassed, typical_physics_steps is updated to allow the new step count for future updates. Care is taken that the modified calculation of the number of physics steps is not observable from game code that only checks the delta parameters to the _process and _physics_process functions; in addition to modifying the number of steps, the _process argument is modified as well to stay in expected bounds. Extra care is taken that the accumulated steps still sum up to roughly the real elapsed time, up to a maximum tolerated difference. To allow the hysteresis code to work correctly on higher refresh monitors, the number of typical physics steps is not only recorded and kept consistent for single render frames, but for groups of them. Currently, up to 12 frames are grouped that way. The engine parameter physics_jitter_fix controls both the maximum tolerated difference between wall clock time and summed up _process arguments and the threshold for changing typical_physics_steps. It is given in units of the real physics frame slice 1/physics_fps. Set physics_jitter_fix to 0 to disable the effects of the new code here. It starts to be effective against the random physics jitter at around 0.02 to 0.05. at values greater than 1 it starts having ill effects on the engine's ability to react sensibly to dropped frames and framerate changes.
125 lines
4.4 KiB
C++
125 lines
4.4 KiB
C++
/*************************************************************************/
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/* engine.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) 2007-2018 Juan Linietsky, Ariel Manzur. */
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/* Copyright (c) 2014-2018 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 ENGINE_H
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#define ENGINE_H
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#include "list.h"
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#include "os/main_loop.h"
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#include "ustring.h"
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#include "vector.h"
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class Engine {
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public:
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struct Singleton {
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StringName name;
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Object *ptr;
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Singleton(const StringName &p_name = StringName(), Object *p_ptr = NULL) :
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name(p_name),
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ptr(p_ptr) {
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}
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};
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private:
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friend class Main;
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uint64_t frames_drawn;
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uint32_t _frame_delay;
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uint64_t _frame_ticks;
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float _frame_step;
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int ips;
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float physics_jitter_fix;
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float _fps;
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int _target_fps;
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float _time_scale;
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bool _pixel_snap;
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uint64_t _physics_frames;
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uint64_t _idle_frames;
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bool _in_physics;
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List<Singleton> singletons;
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Map<StringName, Object *> singleton_ptrs;
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bool editor_hint;
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static Engine *singleton;
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public:
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static Engine *get_singleton();
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virtual void set_iterations_per_second(int p_ips);
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virtual int get_iterations_per_second() const;
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void set_physics_jitter_fix(float p_threshold);
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float get_physics_jitter_fix() const;
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virtual void set_target_fps(int p_fps);
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virtual float get_target_fps() const;
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virtual float get_frames_per_second() const { return _fps; }
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uint64_t get_frames_drawn();
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uint64_t get_physics_frames() const { return _physics_frames; }
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uint64_t get_idle_frames() const { return _idle_frames; }
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bool is_in_physics_frame() const { return _in_physics; }
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uint64_t get_idle_frame_ticks() const { return _frame_ticks; }
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float get_idle_frame_step() const { return _frame_step; }
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void set_time_scale(float p_scale);
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float get_time_scale() const;
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void set_frame_delay(uint32_t p_msec);
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uint32_t get_frame_delay() const;
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void add_singleton(const Singleton &p_singleton);
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void get_singletons(List<Singleton> *p_singletons);
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bool has_singleton(const String &p_name) const;
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Object *get_singleton_object(const String &p_name) const;
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_FORCE_INLINE_ bool get_use_pixel_snap() const { return _pixel_snap; }
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#ifdef TOOLS_ENABLED
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_FORCE_INLINE_ void set_editor_hint(bool p_enabled) { editor_hint = p_enabled; }
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_FORCE_INLINE_ bool is_editor_hint() const { return editor_hint; }
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#else
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_FORCE_INLINE_ void set_editor_hint(bool p_enabled) {}
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_FORCE_INLINE_ bool is_editor_hint() const { return false; }
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#endif
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Dictionary get_version_info() const;
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Engine();
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};
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#endif // ENGINE_H
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