1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
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
|