Vkm::Engine::Clock Class Reference

The engine's frame clock: real + simulation time and the fixed-step accumulator. More...

#include <clock.h>

Public Member Functions
void	beginFrame ()
	Open a new frame: measure the real delta, derive the sim delta, fill the accumulator.
bool	consumeFixedStep ()
	Take one fixed step if one is owed; the main-loop fixedUpdate condition.
void	setTickRate (uint32_t ticksPerSecond)
	Set the simulation cadence, in ticks per second.
void	setPaused (bool paused)
	Pause or resume simulation time.
void	setTimeScale (float scale)
	Set the slow-motion / fast-forward multiplier applied while running.
void	setPacing (float scale)
	Set how many fixed steps a second of wall time buys, as a multiple.
void	requestStep (int steps=1)
	Queue fixed-step advances, whatever the play state.
float	getFixedAlpha () const
	How far into the next fixed step this frame falls, 0..1.
float	getFrameRate () const
	Frames per second, smoothed over roughly the last half second.
float	getFrameTime () const
	The smoothed frame as a duration rather than a rate.
bool	isSimulationStill () const
	Whether the world stands still this frame.
uint32_t	getTick () const
	Which fixed step is running, counting from one.

Detailed Description

The engine's frame clock: real + simulation time and the fixed-step accumulator.

Systems read getDeltaTime() for real-time work (input, camera, UI), getSimDelta() for simulation update() and getFixedStep() in fixedUpdate().

Member Function Documentation

beginFrame()

void Vkm::Engine::Clock::beginFrame

(

)

Open a new frame: measure the real delta, derive the sim delta, fill the accumulator.

The first call reports zero, so a slow startup gives no giant step. A frame longer than Config::MAX_FRAME_ACCUMULATOR is capped, so a hitch discards wall time.

consumeFixedStep()

bool Vkm::Engine::Clock::consumeFixedStep

(

)

Take one fixed step if one is owed; the main-loop fixedUpdate condition.

Requested steps are taken first, then measured time.

Returns

True having taken a step, false once none is owed.

setTickRate()

void Vkm::Engine::Clock::setTickRate ( uint32_t ticksPerSecond )

inline

Set the simulation cadence, in ticks per second.

Set when a project is read, never per frame: fixedUpdate assumes a fixed step.

Parameters

ticksPerSecond

Clamped to [Config::MIN_TICK_RATE, Config::MAX_TICK_RATE].

setPaused()

void Vkm::Engine::Clock::setPaused ( bool paused )

inline

Pause or resume simulation time.

Queued steps survive it.

Parameters

paused

True freezes simulation time (sim delta 0).

setTimeScale()

void Vkm::Engine::Clock::setTimeScale ( float scale )

inline

Set the slow-motion / fast-forward multiplier applied while running.

In the editor a scale lasts one play session; see SceneIOController::endPlaySession.

Parameters

scale

Negative is clamped to 0.

setPacing()

void Vkm::Engine::Clock::setPacing ( float scale )

inline

Set how many fixed steps a second of wall time buys, as a multiple.

A networked client runs slightly fast or slow so the server's command queue neither runs dry nor backs up (NetPacing); the step never changes. Multiplied with the time scale; Engine::run sets it each frame from NetSession::pacing().

Parameters

scale

Negative is clamped to 0.

requestStep()

void Vkm::Engine::Clock::requestStep ( int steps = 1 )

inline

Queue fixed-step advances, whatever the play state.

A count, not seconds: a step is rarely a binary fraction, so n * step converted back would lose ticks.

Parameters

steps

Fixed steps to enqueue; non-positive is ignored.

getFixedAlpha()

float Vkm::Engine::Clock::getFixedAlpha ( ) const

inline

How far into the next fixed step this frame falls, 0..1.

The accumulator's leftover, as a fraction of a step past the last tick.

getFrameRate()

float Vkm::Engine::Clock::getFrameRate ( ) const

inline

Frames per second, smoothed over roughly the last half second.

For this frame alone, use getDeltaTime().

Returns

Zero before the first frame.

getFrameTime()

float Vkm::Engine::Clock::getFrameTime ( ) const

inline

The smoothed frame as a duration rather than a rate.

Returns

Milliseconds per frame; zero before the first frame.

isSimulationStill()

bool Vkm::Engine::Clock::isSimulationStill ( ) const

inline

Whether the world stands still this frame.

True when no simulation time passes and no step is asked for, so no tick can follow; Engine::run drops input latched on such a frame.

getTick()

uint32_t Vkm::Engine::Clock::getTick ( ) const

inline

Which fixed step is running, counting from one.

Advances only when consumeFixedStep() hands one out.

Returns

The tick number; zero before the first.

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The documentation for this class was generated from the following file:

• core/clock.h