Physics Constraints (bge.constraints)

Bullet Physics provides collision detection and rigid body dynamics for the Blender Game Engine.

Features:

  • Vehicle simulation.

  • Rigid body constraints: hinge and point to point (ball socket).

  • Access to internal physics settings, like deactivation time, and debugging features

Note

Note about parameter settings

Since this API is not well documented, it can be unclear what kind of values to use for setting parameters. In general, damping settings should be in the range of 0 to 1 and stiffness settings should not be much higher than about 10.

Examples

See also

For more examples of Bullet physics and how to use them see the pybullet forum.

Example of how to create a hinge Physics Constraint between two objects.

"""
Basic Physics Constraint
++++++++++++++++++++++++
Example of how to create a hinge Physics Constraint between two objects.
"""
from bge import logic
from bge import constraints

# get object list
objects = logic.getCurrentScene().objects

# get object named Object1 and Object 2
object_1 = objects["Object1"]
object_2 = objects["Object2"]

# want to use Edge constraint type
constraint_type = 2

# get Object1 and Object2 physics IDs
physics_id_1 = object_1.getPhysicsId()
physics_id_2 = object_2.getPhysicsId()

# use bottom right edge of Object1 for hinge position
edge_position_x = 1.0
edge_position_y = 0.0
edge_position_z = -1.0

# rotate the pivot z axis about 90 degrees
edge_angle_x = 0.0
edge_angle_y = 0.0
edge_angle_z = 90.0

# create an edge constraint
constraints.createConstraint(physics_id_1, physics_id_2,
                             constraint_type,
                             edge_position_x, edge_position_y, edge_position_z,
                             edge_angle_x, edge_angle_y, edge_angle_z)

Functions

bge.constraints.createConstraint(physicsid_1, physicsid_2, constraint_type, pivot_x=0.0, pivot_y=0.0, pivot_z=0.0, axis_x=0.0, axis_y=0.0, axis_z=0.0, flag=0)

Creates a constraint.

Parameters

  • physicsid_1 (int) – The physics id of the first object in constraint.

  • physicsid_2 (int) – The physics id of the second object in constraint.

  • constraint_type (int) – The type of the constraint, see Create Constraint Constants.

  • pivot_x (float) – Pivot X position. (optional)

  • pivot_y (float) – Pivot Y position. (optional)

  • pivot_z (float) – Pivot Z position. (optional)

  • axis_x (float) – X axis angle in degrees. (optional)

  • axis_y (float) – Y axis angle in degrees. (optional)

  • axis_z (float) – Z axis angle in degrees. (optional)

  • flag (int) – 128 to disable collision between linked bodies. (optional)

Returns

A constraint wrapper.

Return type

KX_ConstraintWrapper

bge.constraints.createVehicle(physicsid)

Creates a vehicle constraint.

Parameters

physicsid (int) – The physics id of the chassis object in constraint.

Returns

A vehicle constraint wrapper.

Return type

KX_VehicleWrapper

bge.constraints.exportBulletFile(filename)

Exports a file representing the dynamics world (usually using .bullet extension).

See Bullet binary serialization.

Parameters

filename (str) – File path.

bge.constraints.getAppliedImpulse(constraintId)
Parameters

constraintId (int) – The id of the constraint.

Returns

The most recent applied impulse.

Return type

float

bge.constraints.getVehicleConstraint(constraintId)
Parameters

constraintId (int) – The id of the vehicle constraint.

Returns

A vehicle constraint object.

Return type

KX_VehicleWrapper

bge.constraints.getCharacter(gameobj)
Parameters

gameobj (KX_GameObject) – The game object with the character physics.

Returns

Character wrapper.

Return type

KX_CharacterWrapper

bge.constraints.removeConstraint(constraintId)

Removes a constraint.

Parameters

constraintId (int) – The id of the constraint to be removed.

bge.constraints.setCcdMode(ccdMode)

Note

Very experimental, not recommended

Sets the CCD (Continous Colision Detection) mode in the Physics Environment.

Parameters

ccdMode (int) – The new CCD mode.

bge.constraints.setContactBreakingTreshold(breakingTreshold)

Note

Reasonable default is 0.02 (if units are meters)

Sets tresholds to do with contact point management.

Parameters

breakingTreshold (float) – The new contact breaking treshold.

bge.constraints.setDeactivationAngularTreshold(angularTreshold)

Sets the angular velocity treshold.

Parameters

angularTreshold (float) – New deactivation angular treshold.

bge.constraints.setDeactivationLinearTreshold(linearTreshold)

Sets the linear velocity treshold.

Parameters

linearTreshold (float) – New deactivation linear treshold.

bge.constraints.setDeactivationTime(time)

Sets the time after which a resting rigidbody gets deactived.

Parameters

time (float) – The deactivation time.

bge.constraints.setDebugMode(mode)

Sets the debug mode.

Parameters

mode (int) – The new debug mode, see Debug Mode Constants.

bge.constraints.setGravity(x, y, z)

Sets the gravity force.

Parameters

  • x (float) – Gravity X force.

  • y (float) – Gravity Y force.

  • z (float) – Gravity Z force.

bge.constraints.setLinearAirDamping(damping)

Note

Not implemented

Sets the linear air damping for rigidbodies.

bge.constraints.setNumIterations(numiter)

Sets the number of iterations for an iterative constraint solver.

Parameters

numiter (int) – New number of iterations.

bge.constraints.setNumTimeSubSteps(numsubstep)

Sets the number of substeps for each physics proceed. Tradeoff quality for performance.

Parameters

numsubstep (int) – New number of substeps.

bge.constraints.setSolverDamping(damping)

Note

Very experimental, not recommended

Sets the damper constant of a penalty based solver.

Parameters

damping (float) – New damping for the solver.

bge.constraints.setSolverTau(tau)

Note

Very experimental, not recommended

Sets the spring constant of a penalty based solver.

Parameters

tau (float) – New tau for the solver.

bge.constraints.setSolverType(solverType)

Note

Very experimental, not recommended

Sets the solver type.

Parameters

solverType (int) – The new type of the solver.

bge.constraints.setSorConstant(sor)

Note

Very experimental, not recommended

Sets the successive overrelaxation constant.

Parameters

sor (float) – New sor value.

bge.constraints.setUseEpa(epa)

Note

Not implemented

Constants

bge.constraints.error

Symbolic constant string that indicates error.

Type

str

Debug Mode Constants

Debug mode to be used with setDebugMode().

bge.constraints.DBG_NODEBUG

No debug.

Value

0

bge.constraints.DBG_DRAWWIREFRAME

Draw wireframe in debug.

Value

1

bge.constraints.DBG_DRAWAABB

Draw Axis Aligned Bounding Box in debug.

Value

2

bge.constraints.DBG_DRAWFREATURESTEXT

Draw features text in debug.

Value

4

bge.constraints.DBG_DRAWCONTACTPOINTS

Draw contact points in debug.

Value

8

bge.constraints.DBG_NOHELPTEXT

Debug without help text.

Value

32

bge.constraints.DBG_DRAWTEXT

Draw text in debug.

Value

64

bge.constraints.DBG_PROFILETIMINGS

Draw profile timings in debug.

Value

128

bge.constraints.DBG_ENABLESATCOMPARISION

Enable sat comparision in debug.

Value

256

bge.constraints.DBG_DISABLEBULLETLCP

Disable Bullet LCP.

Value

512

bge.constraints.DBG_ENABLECCD

Enable Continous Collision Detection in debug.

Value

1024

bge.constraints.DBG_DRAWCONSTRAINTS

Draw constraints in debug.

Value

2048

bge.constraints.DBG_DRAWCONSTRAINTLIMITS

Draw constraint limits in debug.

Value

4096

bge.constraints.DBG_FASTWIREFRAME

Draw a fast wireframe in debug.

Value

8192

Create Constraint Constants

Constraint type to be used with createConstraint().

bge.constraints.POINTTOPOINT_CONSTRAINT
Value

1

bge.constraints.LINEHINGE_CONSTRAINT
Value

2

bge.constraints.ANGULAR_CONSTRAINT
Value

3

bge.constraints.CONETWIST_CONSTRAINT
Value

4

bge.constraints.VEHICLE_CONSTRAINT
Value

11

bge.constraints.GENERIC_6DOF_CONSTRAINT
Value

12