Constraints

Constraints Overview

Selects and manages native Jolt solver relationships between bodies or between one body and the fixed world.

A constraint removes or controls relative degrees of freedom. Choose the narrowest type that describes the intended mechanism: simpler constraints are easier to configure, explain and tune than a fully general SixDOF joint.

Constraint selection#

Type	Permitted relative motion	Limits / drive	World variant
Fixed	None; preserves complete relative transform	No limits or motor	Yes
Point	All rotation around one shared point	No angular limits or motor	Yes
Distance	Free orientation within a length range	Min/max distance and spring	Yes
Hinge	One rotational axis	Angular limits, torque motor and spring	Yes
Slider	One linear axis	Linear limits, force motor and spring	Yes
Cone	Circular bounded swing plus free twist	Single swing half-angle	Yes
SwingTwist	Elliptical swing and bounded twist	Friction plus separate swing/twist motors	No
SixDOF	Any axis may be fixed, free or limited	Per-axis friction, limits and motors	No
Pulley	Two lengths coupled through a ratio	Total length range	No
Path	Travel along a Hermite curve	Path motor, friction and rotation modes	Separate Paths section

Public creators#

Factory	Usage
jolt_fixed	See the specific constraint reference for required arguments.
jolt_point	See the specific constraint reference for required arguments.
jolt_distance	See the specific constraint reference for required arguments.
jolt_hinge	See the specific constraint reference for required arguments.
jolt_slider	See the specific constraint reference for required arguments.
jolt_cone	See the specific constraint reference for required arguments.
jolt_swing_twist	See the specific constraint reference for required arguments.
jolt_sixdof	See the specific constraint reference for required arguments.
jolt_pulley	See the specific constraint reference for required arguments.
jolt_path	See the specific constraint reference for required arguments.

Common creation contract#

Managed creators require jolt_start() and resources belonging to its active default world.
Body-to-body creators require two different live JoltBody wrappers in that same world.
Static-dynamic, kinematic-dynamic and dynamic-dynamic mechanisms are supported; unsupported static-static configurations fail natively.
Creators return JoltConstraint on success or undefined on failure. Read jolt_get_error() for code, message and context.
Public positions, anchors and ordinary axes are right-handed world-space X/Y/Z with Z up unless a page explicitly documents COM-local or constraint-space data.

Shared runtime interface#

Method	Meaning
is_valid()	Checks the wrapper, managed world and native generational handle.
get_native_handle()	Returns an opaque handle for diagnostics/advanced interop, or 0 when invalid.
destroy()	Idempotently removes this constraint only.
set_enabled() / get_enabled()	Temporarily changes solver participation.
set_collision_enabled() / get_collision_enabled()	Controls collision for the connected user-body pair.

Collision policy#

Classic body-to-body constraints default collision to true. SwingTwist and SixDOF default it to false. Disabling collision affects only that connected pair and is reference-counted when several constraints suppress the same pair. World variants have no second user body and always report false.

Update and cleanup order#

jolt_start();
// Create bodies and constraints.

// Step event:
jolt_update();

// Cleanup when needed:
joint.destroy();
body_a.destroy();
body_b.destroy();
jolt_stop();

Debug drawing#

jolt_debug_enable(true);
jolt_debug_set(JOLT_DEBUG_CONSTRAINTS, true);

// Draw End, after opaque scene geometry:
jolt_debug_draw();

The constraint debug layer visualizes live anchors, frames, limits, motors and type-specific solver geometry. It changes no simulation state.