72 lines
2.5 KiB
C++
72 lines
2.5 KiB
C++
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#ifndef TIMER_SYNC_H
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#define TIMER_SYNC_H
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#include "core/engine.h"
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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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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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// 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 // TIMER_SYNC_H
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