Time Control¶

ivf2 provides a global time controller that lets you pause, resume, and scale time across your entire scene — animations, deformers, particle systems, and any custom logic that depends on elapsed time.

Why TimeController?¶

GLFWWindow exposes elapsedTime() and frameTime() tied to the wall clock. They cannot be paused or slowed. TimeController adds a logical time layer on top: the same real delta is fed in each frame, but your code reads a scaled, pausable version. All systems that consume TimeController::elapsed() or delta() automatically respect the current state.

Basic Usage¶

Include the header (already part of <ivf/gl.h>) and read from the singleton in onUpdate():

#include <ivf/time_controller.h>

void onUpdate() override
{
    auto *tc = ivf::TimeController::instance();
    double t  = tc->elapsed();   // accumulated scaled time (seconds)
    double dt = tc->delta();     // scaled frame delta (0 when paused)

    m_wave->setTime(static_cast<float>(t));
    m_particles->update(static_cast<float>(dt));
}

GLFWSceneWindow feeds the real frame delta into TimeController automatically — you never call update() yourself.

Pause and Resume¶

void onKey(int key, int, int action, int) override
{
    if (action != GLFW_PRESS) return;
    auto *tc = ivf::TimeController::instance();

    if (key == GLFW_KEY_SPACE)
        tc->togglePause();          // flip pause state
    else if (key == GLFW_KEY_P)
        tc->pause();
    else if (key == GLFW_KEY_R)
        tc->resume();
}

When paused, delta() returns 0.0 and elapsed() stops accumulating. Systems driven by delta() freeze in place automatically.

Time Scaling¶

Scale adjusts how fast logical time runs relative to wall time. A scale of 0.5 gives half-speed slow motion; 2.0 doubles the animation speed.

auto *tc = ivf::TimeController::instance();

tc->setScale(0.5f);  // half speed — slow motion
tc->setScale(2.0f);  // double speed
tc->setScale(0.0f);  // freeze (equivalent to pause but scale stays 0)
tc->setScale(1.0f);  // back to normal

Scale and pause are independent. A paused controller at scale 2.0 resumes at double speed.

// Increase/decrease with keyboard
if (key == GLFW_KEY_EQUAL)
    tc->setScale(std::min(4.0f, tc->scale() + 0.1f));
else if (key == GLFW_KEY_MINUS)
    tc->setScale(std::max(0.0f, tc->scale() - 0.1f));

Reset¶

tc->reset();   // sets elapsed back to 0; scale and pause state unchanged

Useful for restarting a scene or resynchronising looping animations.

API Reference¶

TimeControlPanel¶

The easiest way to expose time control to users is the built-in ImGui panel:

#include <ivfui/time_control_panel.h>

int onSetup() override
{
    addUiWindow(ivfui::TimeControlPanel::create());
    return 0;
}

The panel provides a pause/resume button, a time-scale slider (0–4×), a reset button, and a live readout of elapsed time. See Time Control Panel for details.