dynamiclinkage

Interface to dynamic compatible joints

The dynamiclinkage module is an interface between Pymunk and a kinematic linkage.

It provides various classes to overwrite the pylinkage.Joint objects. It also includes a DynamicLinkage that inherits from pylinkage.linkage.Linkage. Eventually a handy convert_to_dynamic_linkage method can generate a DynamicLinkage from a pylinkage.linkage.Linkage.

class leggedsnake.dynamiclinkage.DynamicJoint(body0=None, body1=None, space=None, radius=0.3, density=1, shape_filter=None)

Bases: ABC

Dynamic, pymunk compatible equivalent of kinematic Joint.

__init__(body0=None, body1=None, space=None, radius=0.3, density=1, shape_filter=None)

Partial class to generate a DynamicJoint.

A DynamicJoint is a Joint that can handle Pymunk Bodies.

Parameters:

body0 (pymunk.body.Body, optional) – First Body to link to. The default is None.
body1 (pymunk.body.Body, optional) – Second Body to link to. The default is None
space (pymunk.space.Space, optional) – Simulation space in which the DynamicJoint exists. The default is None.
radius (float, optional) – DynamicJoint will generate hulls of this radius. The default is .3.
density (float, optional) – Density of the hull, mass will be computed accordingly. The default is 1.
shape_filter (pymunk.shapes.ShapeFilter, optional) – Prevent hulls from colliding with each other. Useful is the same linkage for instance. The default is None.

_abc_impl = <_abc._abc_data object>

reload()

Reload DynamicJoint coordinates.

Coordinates only depend on Body position and DO NOT use any linkage constraint.

Return type:: None.

class leggedsnake.dynamiclinkage.DynamicLinkage(joints, space, density=1, load=0, name=None, thickness=0.1)

Bases: Linkage

Dynamic counterpart of a kinematic linkage.Linkage.

It has several attributes linked to its dynamic nature and is close to an empty shell in the ways you will use it.

Please note that it carries a load, which is relevant with real-world simulation where the weight of legs is small compared to the weight of the frame.

__init__(joints, space, density=1, load=0, name=None, thickness=0.1)

Instanciate a new DynamicLinkage.

Parameters:

joints (linkage.Joint) – Joints to be part of the linkage. Kinematic joints will be converted to their dynamic equivalents.
space (pymunk.Space) – Space in which linkage should be instantiated.
density (float, optional) – Density of the Bodies in the linkage. The default is 1.
load (float, optional) – Mass of the load to carry. The default is 0.
name (TYPE, optional) – User-friendly name for the linkage. The default is None. It will be set to str(id(self)) if not provided.
thickness (float, optional) – ratio bar length/width for each bar (radius in pymunk). The default is .1.

Return type:

None.

_thickness

body

build_load(position, load_mass): Create the load this linkage has to carry.

convert_to_dynamic_joints(joints): Convert a kinematic joint in its dynamic counterpart.

density

filter

height

joint_to_rigidbodies

mass

mechanical_energy

rigidbodies

space

class leggedsnake.dynamiclinkage.DynamicPivot(x=0, y=0, joint0=None, space=None, joint1=None, distance0=None, distance1=None, name=None, radius=0.3, density=1, shape_filter=None)

Bases: Pivot, DynamicJoint

Dynamic counterpart of a Pivot joint.

__init__(x=0, y=0, joint0=None, space=None, joint1=None, distance0=None, distance1=None, name=None, radius=0.3, density=1, shape_filter=None)

Set point position, parents, and if it is fixed for this turn.

Parameters:

x (float, optional) – Position on horizontal axis. The default is 0.
y (float, optional) – Position on vertical axis. The default is O.
name (str, optional) – Friendly name for human readability. The default is None.
joint0 (Union[Joint, tuple[float]], optional) – Linked pivot joint 1 (geometric constraints). The default is None.
joint1 (Union[Joint, tuple[float]], optional) – Other pivot joint linked. The default is None.
distance0 (float, optional) – Distance from joint0 to the current Joint. The default is None.
distance1 (float, optional) – Distance from joint1 to the current Joint. The default is None.

_abc_impl = <_abc._abc_data object>

r0

r1

reload()

Reload DynamicJoint coordinates.

Coordinates only depend on Body position and DO NOT use any linkage constraint.

Return type:: None.

set_anchor_a(joint, distance=None)

Set anchor_a characteristics.

Parameters:

joint (DynamicJoint) – DynamicJoint to use as anchor_a.
distance (float, optional) – Distance to keep constant between anchor_a and self. The default is None.

Return type:

None.

set_anchor_b(joint, distance=None)

Set anchor_b characteristics.

Parameters:

joint (DynamicJoint) – DynamicJoint to use as anchor_b.
distance (float, optional) – Distance to keep constant between anchor_b and self. The default is None.

Return type:

None.

class leggedsnake.dynamiclinkage.Motor(x=None, y=None, joint0=None, space=None, distance=None, angle=None, name=None, radius=0.3, density=1, shape_filter=None)

Bases: Crank, DynamicJoint

A Motor is a crank.

It makes a link between a body and a second link it creates. It attaches them with a PivotJoint, and adds a SimpleMotor over it. The bodies are now constrained to rotate around one each other.

The Motor is placed at the extremity of the body it creates.

__init__(x=None, y=None, joint0=None, space=None, distance=None, angle=None, name=None, radius=0.3, density=1, shape_filter=None)

Define a crank (circular motor).

Parameters:

x (float, optional) – initial horizontal position, won’t be used thereafter. The default is None.
y (float, optional) – initial vertical position. The default is None.
joint0 (Union[Joint, tuple[float]], optional) – first reference joint. The default is None.
distance (float, optional) – distance to keep between joint0 and self. The default is None.
angle (float, optional) – It is the angle (horizontal axis, joint0, self). Should be in radian and in trigonometric order. The default is None.
name (str, optional) – user-friendly name. The default is None.

Return type:

None.

_abc_impl = <_abc._abc_data object>

angle

r

reload()

Reload DynamicJoint coordinates.

Coordinates only depend on Body position and DO NOT use any linkage constraint.

Return type:: None.

set_anchor_a(joint, distance=None)

Set anchor_a characteristics.

Parameters:

joint (DynamicJoint) – DynamicJoint to use as anchor_a.
distance (float, optional) – Distance to keep constant between anchor_a and self. The default is None.

Return type:

None.

class leggedsnake.dynamiclinkage.Nail(x=0, y=0, name=None, body=None, space=None, radius=0.3, density=1, shape_filter=None)

Bases: Static, DynamicJoint

A simple point to follow a rigidbody.

It is special since it DOES NOT generate bodies.

__init__(x=0, y=0, name=None, body=None, space=None, radius=0.3, density=1, shape_filter=None)

A Static joint is a point in space to use as anchor by other joints.

It is NOT a kind of joint as viewed in engineering terms!

xfloat, optional: Position on horizontal axis. The default is 0.
yfloat, optional: Position on vertical axis. The default is O.
namestr, optional: Friendly name for human readability. The default is None.

_abc_impl = <_abc._abc_data object>

reload(): Reload position based on linked body rotation and position.

class leggedsnake.dynamiclinkage.PinUp(x=0, y=0, joint0=None, space=None, joint1=None, distance=None, angle=None, name=None, radius=0.3, density=1, shape_filter=None)

Bases: Fixed, DynamicJoint

Dynamic counterpart of Fixed joint.

Add two pm.Segment to the linked body.

__init__(x=0, y=0, joint0=None, space=None, joint1=None, distance=None, angle=None, name=None, radius=0.3, density=1, shape_filter=None)

Create a point, of position fully defined by its two references.

Parameters:

x (float, optional) – Position on horizontal axis. The default is 0.
y (float, optional) – Position on vertical axis. The default is O.
name (str, optional) – Friendly name for human readability. The default is None.
joint0 (Union[Joint, tuple[float]], optional) – Linked pivot joint 1 (geometric constraints). The default is None.
joint1 (Union[Joint, tuple[float]], optional) – Other pivot joint linked. The default is None.
distance (float, optional) – Distance to keep constant between joint0 and self. The default is None.
angle (float, optional) – Angle (joint1, joint0, self). Should be in radian and in trigonometric order. The default is None.

_abc_impl = <_abc._abc_data object>

angle

r

reload()

Reload DynamicJoint coordinates.

Coordinates only depend on Body position and DO NOT use any linkage constraint.

Return type:: None.

set_anchor_a(joint, distance=None, angle=None)

Set first anchor characteristics.

Parameters:

joint (DynamicJoint) – DynamicJoint to use as anchor_a.
distance (float, optional) – Distance to keep constant. The default is None.
angle (float, optional) – Angle (in radians) (joint1, joint0, self). The default is None.

Return type:

None.

set_anchor_b(joint)

Set second anchor characteristics.

It will create errors if called before anchor_a is properly defined. SIDE EFFECT: creates two Segment objects and adds them to self.space.

Parameters:: joint (DynamicJoint) – Joint to use as anchor_b.
Return type:: None.

leggedsnake.dynamiclinkage.convert_to_dynamic_linkage(kinematic_linkage, space, density=1, load=1): Convert a classic Linkage to its dynamic counterpart.