Visualization

GLFW window management and the real-time render/tick loop. More...

Classes
struct	mj_kdl::Viewer

Functions
bool	mj_kdl::init_window (Viewer *v, Robot *r, const char *title="MuJoCo", int width=1280, int height=720)
bool	mj_kdl::init_window_sim (Viewer *v, Robot *r, const char *title="MuJoCo")
void	mj_kdl::cleanup (Viewer *v)
bool	mj_kdl::is_running (const Viewer *v)
bool	mj_kdl::render (Viewer *v, const Robot *r)
bool	mj_kdl::render (Viewer *v, mjModel *m, mjData *d)
bool	mj_kdl::tick (Viewer *v, Robot *r)
bool	mj_kdl::tick (Viewer *v, mjModel *m, mjData *d)

Detailed Description

GLFW window management and the real-time render/tick loop.

Use init_window_sim() + tick() for the full simulate UI with physics panels. Use init_window() + render() for a lightweight manual render loop.

Function Documentation

cleanup()

void mj_kdl::cleanup

(

Viewer *

v

)

Release the GLFW window and MuJoCo visualization contexts owned by v.

Parameters

[in,out]

v

Viewer to tear down; all pointers set to null afterwards.

init_window()

bool mj_kdl::init_window	(	Viewer *	v,
		Robot *	r,
		const char *	title = "MuJoCo",
		int	width = 1280,
		int	height = 720
	)

Open a GLFW window and initialise MuJoCo visualization contexts. Must be called after init_robot() or init_from_mjcf().

Parameters

[out]	v	Viewer to initialise; must be zero-initialised before call.
[in]	r	Robot whose model drives the rendering context.
[in]	title	Window title string.
[in]	width	Window width in pixels.
[in]	height	Window height in pixels.

Returns

true on success, false if GLFW or MuJoCo context creation fails.

init_window_sim()

bool mj_kdl::init_window_sim	(	Viewer *	v,
		Robot *	r,
		const char *	title = "MuJoCo"
	)

Open the full MuJoCo simulate UI (panels, physics controls, joint viewer) in a background render thread, then return so the caller can drive the physics loop with tick().

Use this instead of init_window() when you want the simulate UI panels alongside a user-owned loop. tick() automatically acquires the render mutex, steps physics, and handles pause / perturbation / speed controls.

Note: the render thread owns the GLFW window; on Linux (X11 / Wayland) this works correctly. Not supported on macOS.

Parameters

[out]	v	Viewer to initialise; freed by cleanup(Viewer *).
[in]	r	Robot to simulate.
[in]	title	Label shown in the window title bar (default "MuJoCo").

Returns

true on success.

Referenced by main().

is_running()

bool mj_kdl::is_running

(

const Viewer *

v

)

Returns true if the viewer window is open and not scheduled for closing.

Parameters

[in]

v

Viewer created by init_window().

render() [1/2]

bool mj_kdl::render	(	Viewer *	v,
		const Robot *	r
	)

Render the current simulation frame to the viewer window.

Parameters

[in,out]	v	Viewer created by init_window().
[in]	r	Robot whose model and data are rendered.

Returns

true if the window is still open after rendering.

render() [2/2]

bool mj_kdl::render	(	Viewer *	v,
		mjModel *	m,
		mjData *	d
	)

Render the current simulation frame to the viewer window. Model/data overload – use when no single Robot owns the scene (e.g. multi-robot).

Parameters

[in,out]	v	Viewer created by init_window().
[in]	m	MuJoCo model.
[in]	d	MuJoCo data.

Returns

true if the window is still open after rendering.

tick() [1/2]

bool mj_kdl::tick	(	Viewer *	v,
		mjModel *	m,
		mjData *	d
	)

Model/data overload of tick() for multi-robot or model-owned loops where no single Robot is the canonical owner of the scene. Physics always runs (paused state is not tracked; use the sim UI pause button when using init_window_sim, or manage it externally for init_window).

Parameters

[in,out]	v	Viewer initialised by init_window() or init_window_sim().
[in]	m	Shared MuJoCo model.
[in]	d	Shared MuJoCo data.

Returns

true while the window is open; false once the user closes it.

tick() [2/2]

bool mj_kdl::tick	(	Viewer *	v,
		Robot *	r
	)

Advance one physics step, render, sync to real time, and poll GLFW events. Intended for user-owned control loops; call once per control cycle.

Sequence inside tick():

1. glfwPollEvents() – fires keyboard / mouse callbacks
2. real-time sleep – paces the loop to model->opt.timestep wall time
3. if (!r->paused): apply mouse perturbation forces (if active) mj_step()
4. render()

update() is NOT called here – call it yourself to read *_msr and apply *_cmd. Typical loop:

update(&robot); // seed initial sensor readings while (tick(&viewer, &robot)) { my_control_step(&robot); // reads *_msr, writes *_cmd update(&robot); // applies *_cmd, refreshes *_msr for next step }

Returns

true while the window is open; false once the user closes it.

Referenced by main().