Source code for klampt.model.coordinates

"""A module to help manage coordinate frames and objects attached to them.
Similar to the tf module in ROS.

You may attach points / vectors to frames and determine relative or world
coordinates in a straightforward, object-oriented way.

The ``coordinates`` module is set up with a default coordinate manager so that
if you call ``coordinates.[X]``, where ``[X]`` is a method of
:class:`klampt.model.coordinates.Manager`, such as ``setWorldModel()``,
``addPoint()``, ``addFrame()``, etc., then the default ``Manager``
instance gets called.

Advanced users might create their own ``Manager``, or swap top-level managers
in/out using :meth:`setManager`.
"""

from ..math import so3,se3,vectorops
from ..robotsim import IKObjective, RobotModelLink,RigidObjectModel,SimRobotController
from . import ik
from collections import defaultdict
from typing import Optional, Union

[docs]class Frame: """Represents some coordinate frame in space.""" def __init__(self,name,worldCoordinates=se3.identity(), parent=None,relativeCoordinates=None): self._name = name self._parent = parent self._worldCoordinates = worldCoordinates self._data = None if relativeCoordinates == None: if worldCoordinates == None: raise ValueError("One of relativeCoordinates or worldCoordinates must be provided") if parent == None: self._relativeCoordinates = worldCoordinates else: self._relativeCoordinates = se3.mul(se3.inv(parent.worldCoordinates()),worldCoordinates) else: self._relativeCoordinates = relativeCoordinates if worldCoordinates == None: if parent == None: self._worldCoordinates = relativeCoordinates else: self._worldCoordinates = se3.mul(parent.worldCoordinates(),relativeCoordinates)
[docs] def name(self): """Returns the name of this frame""" return self._name
[docs] def data(self): """If any data is attached to this frame, returns it""" return self._data
[docs] def worldOrigin(self): """Returns an element of R^3 denoting the translation of the origin of this frame in world coordinates""" return self._worldCoordinates[1]
[docs] def relativeOrigin(self): """Returns an element of R^3 denoting the translation of the origin of this frame relative to its parent""" return self._relativeCoordinates[1]
[docs] def worldRotation(self): """Returns an element of SO(3) denoting the rotation from this frame to world coordinates""" return self._worldCoordinates[0]
[docs] def relativeRotation(self): """Returns an element of SO(3) denoting the rotation from this frame to its parent""" return self._relativeCoordinates[0]
[docs] def worldCoordinates(self): """Returns an element of SE(3) denoting the transform from this frame to world coordinates""" return self._worldCoordinates
[docs] def relativeCoordinates(self): """Returns an element of SE(3) denoting the transform from this frame to its parent""" return self._relativeCoordinates
[docs] def parent(self): """Returns the parent of the frame, or None if it's given in the world frame.""" return self._parent
[docs]class Transform: """A transform from one Frame (source) to another (destination). The destination may be None, in which case the transform is the world transform of the source. The difference between a Transform and a relative Frame (i.e., one with a parent) is that a Transform is a sort of "read-only" structure whose coordinates change as the frames' coordinates change.""" def __init__(self,source,destination=None): assert isinstance(source,Frame) if destination is not None: assert isinstance(destination,Frame) self._name = None self._source = source self._destination = destination
[docs] def source(self) -> Frame: """Returns the source Frame""" return self._source
[docs] def destination(self) -> Frame: """Returns the source Frame""" return self._destination
[docs] def coordinates(self): """Returns the SE(3) coordinates that transform elements from the source to the destination Frame.""" if self._destination==None: return self._source.worldCoordinates() return se3.mul(se3.inv(self._destination.worldCoordinates()),self._source.worldCoordinates())
[docs] def translationCoordinates(self): """Returns the coordinates of the origin of this frame in R^3, relative to its destination""" if self._destination==None: return self._source.worldOrigin() return se3.apply(se3.inv(self._destination.worldCoordinates()),self._source.worldOrigin())
[docs] def rotationCoordinates(self): """Returns the SO(3) coordinates that rotate elements from the source to the destination Frame""" if self._destination==None: return self._source.worldRotation() return so3.mul(so3.inv(self._destination.worldRotation()),self._source.worldRotation())
[docs] def toWorld(self): """Returns a Transform designating the transformation from the source frame to the world frame.""" return Transform(self.source,None)
[docs] def to(self,frame): """Returns a Transform designating the transformation from the source frame to the given frame.""" return Transform(self.source,frame)
[docs]class Point: """Represents a point in 3D space. It is attached to a frame, so if the frame is changed then its world coordinates will also change.""" def __init__(self,localCoordinates=[0,0,0],frame=None): if frame is not None: assert isinstance(frame,Frame) self._name = None self._localCoordinates = localCoordinates self._frame = frame
[docs] def localCoordinates(self): """Returns the coordinates of this point in its parent Frame""" return self._localCoordinates[:]
[docs] def worldCoordinates(self): """Returns the coordinates of this point in the world Frame""" if self._frame ==None: return self._localCoordinates[:] return se3.apply(self._frame.worldCoordinates(),self._localCoordinates)
[docs] def frame(self) -> Frame: """Returns the frame to which this Point is attached""" return self._frame
[docs] def toWorld(self) -> 'Point': """Returns a Point representing the same point in space, but in the world reference frame""" return Point(self.worldCoordinates(),None)
[docs] def to(self,newframe): """Returns a Point representing the same point in space, but in a different reference frame""" if newframe == None or newframe=='world': return self.toWorld() newlocal = se3.apply(se3.inv(newframe.worldCoordinates()),self.worldCoordinates()) return Point(newlocal,newframe)
[docs] def localOffset(self,dir): """Offsets this point by a vector in local coordinates""" self._localCoordinates = vectorops.add(self._localCoordinates,dir)
[docs] def worldOffset(self,dir): """Offsets this point by a vector in world coordinates""" if self._frame == None: self._localCoordinates = vectorops.add(self._localCoordinates,dir) else: self._localCoordinates = vectorops.add(so3.apply(so3.inv(self._frame.worldCoordinates()[0]),self._localCoordinates),dir)
[docs]class Direction: """Represents a directional quantity in 3D space. It is attached to a frame, so if the frame is rotated then its world coordinates will also change.""" def __init__(self,localCoordinates=[0,0,0],frame=None): if frame is not None: assert isinstance(frame,Frame) self._name = None self._localCoordinates = localCoordinates self._frame = frame
[docs] def localCoordinates(self): return self._localCoordinates[:]
[docs] def worldCoordinates(self): if self._frame ==None: return self._localCoordinates[:] return so3.apply(self._frame.worldCoordinates()[0],self._localCoordinates)
[docs] def frame(self) -> Frame: return self._frame
[docs] def toWorld(self) -> 'Direction': """Returns a Direction representing the same direction in space, but in the world reference frame""" return Direction(self.worldCoordinates(),None)
[docs] def to(self,newframe): """Returns a Direction representing the same direction in space, but in a different reference frame""" if newframe == None or newframe=='world': return self.toWorld() newlocal = so3.apply(so3.inv(newframe.worldCoordinates()[0]),self.worldCoordinates()) return Direction(newlocal,newframe)
[docs] def scale(self,amount): """Scales this direction by a scalar amount""" self._localCoordinates = vectorops.mul(self._localCoordinates,amount)
[docs] def localOffset(self,dir): """Offsets this direction by a vector in local coordinates""" self._localCoordinates = vectorops.add(self._localCoordinates,dir)
[docs] def worldOffset(self,dir): """Offsets this direction by a vector in world coordinates""" if self._frame == None: self._localCoordinates = vectorops.add(self._localCoordinates,dir) else: self._localCoordinates = vectorops.add(so3.apply(so3.inv(self._frame.worldCoordinates()[0]),self._localCoordinates),dir)
[docs]class Group: """A collection of Frames, Points, Directions, and sub-Groups. All groups have a privileged frame called 'root'. The default manager is a Group with a privileged frame called 'world' which is just an alias for 'root'. Subgroup items can be accessed using the syntax [group]:[itemname]. Subgroups can also be nested. Attributes: frames (dict): a map from frame names to Frame objects childLists (dict): a map from frame names to lists of children points (dict): a map from point names to Point objects directions (dict): a map from direction names to Direction objects subgroups (dict): a map from subgroup names to Group objects """ def __init__(self): self._name = None self.destroy()
[docs] def rootFrame(self) -> Optional[Frame]: return self.frames.get('root',None)
[docs] def destroy(self): """Call this to destroy a group cleanly""" self.frames = {} self.childLists = defaultdict(list) self.frames['root'] = Frame('root') self.points = {} self.directions = {} self.subgroups = {}
[docs] def setWorldModel(self,worldModel): """Sets this group to contain all entities of a world model""" for i in range(worldModel.numRobots()): rgroup = self.addGroup(worldModel.robot(i).getName()) rgroup.setRobotModel(worldModel.robot(i)) for i in range(worldModel.numRigidObjects()): try: f = self.addFrame(worldModel.rigidObject(i).getName(),worldCoordinates=worldModel.rigidObject(i).getTransform()) f._data = worldModel.rigidObject(i) except ValueError: f = self.addFrame("%s[%d]"%(worldModel.rigidObject(i).getName(),i),worldCoordinates=worldModel.rigidObject(i).getTransform()) f._data = worldModel.rigidObject(i) for i in range(worldModel.numTerrains()): try: f = self.addFrame(worldModel.terrain(i).getName(),worldCoordinates=se3.identity()) f._data = worldModel.terrain(i) except ValueError: f = self.addFrame("%s[%d]"%(worldModel.terrain(i).getName(),i),worldCoordinates=se3.identity()) f._data = worldModel.terrain(i) return
[docs] def setRobotModel(self,robotModel): """Sets this group to contain all links of a robot model""" root = self.frames['root'] for i in range(robotModel.numLinks()): p = robotModel.link(i).getParent() if p >= 0: Fp = self.frames[robotModel.link(p).getName()] else: Fp = root f = self.addFrame(robotModel.link(i).getName(),worldCoordinates=robotModel.link(i).getTransform(),parent=Fp) f._data = robotModel.link(i) return
[docs] def setController(self,controller): """Given a SimRobotController, sets this group to contain all sensed and commanded frames.""" root = self.frames['root'] robot = controller.robot() robot.setConfig(controller.getCommandedConfig()) for i in range(robot.numLinks()): p = robot.link(i).getParent() if p >= 0: Fp = self.frames[robot.link(p).getName()+"_commanded"] else: Fp = root f = self.addFrame(robot.link(i).getName()+"_commanded",worldCoordinates=robot.link(i).getTransform(),parent=Fp) f._data = (controller,i,'commanded') robot.setConfig(controller.getSensedConfig()) for i in range(robot.numLinks()): p = robot.link(i).getParent() if p >= 0: Fp = self.frames[robot.link(p).getName()+"_commanded"] else: Fp = root f = self.addFrame(robot.link(i).getName()+"_sensed",worldCoordinates=robot.link(i).getTransform(),parent=Fp) f._data = (controller,i,'sensed') return
[docs] def setSimBody(self,name,simBody): """Sets this group to be attached to a simBody""" f = self.addFrame(name,worldCoordinates=simBody.getTransform()) f._data = simBody return
[docs] def updateFromWorld(self): """For any frames with associated world elements, updates the transforms from the world elements.""" for (n,f) in self.frames.items(): if f._data == None: continue if hasattr(f._data,'getTransform'): worldCoordinates = f._data.getTransform() if hasattr(f._data,'getParent'): p = f._data.getParent() if p >= 0: plink = f._data.robot().link(p) parentCoordinates = plink.getTransform() f._relativeCoordinates = se3.mul(se3.inv(parentCoordinates),worldCoordinates) else: f._relativeCoordinates = worldCoordinates else: f._relativeCoordinates = worldCoordinates f._worldCoordinates = worldCoordinates #update downstream non-link items for c in self.childLists[f._name]: if c._data == None or not hasattr(c._data,'getTransform'): c._worldCoordinates = se3.mul(f._worldCoordinates,c._relativeCoordinates) self.updateDependentFrames(c) if isinstance(f._data,tuple) and isinstance(f._data[0],SimRobotController): controller,index,itemtype = f._data #TODO: update the frame from the controller data for (n,g) in self.subgroups.items(): g.updateFromWorld()
[docs] def updateToWorld(self): """For any frames with associated world elements, updates the transforms of the world elements. Note: this does NOT perform inverse kinematics!""" for (n,f) in self.frames.items(): if f.data == None: continue if hasattr(f.data,'setTransform'): f.data.setTransform(*f.worldCoordinates()) for (n,g) in self.subgroups.items(): g.updateToWorld()
[docs] def addFrame(self,name,worldCoordinates=None,parent=None,relativeCoordinates=None): """Adds a new named Frame, possibly with a parent. 'parent' may either be a string identifying another named Frame in this Group, or it can be a Frame object. (Warning: unknown behavior may result from specifying a Frame not in this Group). Either worldCoordinates or relativeCoordinates must be given. If worldCoordinates is given, then the frame's initial relative transform is determined by the current coordinates of the parent. If all parameters are left as default, the frame is placed directly at the origin of the parent""" if name in self.frames: raise ValueError("Frame "+name+" already exists") if parent==None: parent = 'root' if isinstance(parent,str): parent = self.frames[parent] if worldCoordinates == None and relativeCoordinates == None: relativeCoordinates = se3.identity() self.frames[name] = Frame(name,worldCoordinates=worldCoordinates,parent=parent,relativeCoordinates=relativeCoordinates) self.childLists[parent._name].append(self.frames[name]) return self.frames[name]
[docs] def addPoint(self,name,coordinates=[0,0,0],frame='root'): if name in self.points: raise ValueError("Point "+name+" already exists") res = self.point(coordinates,frame) res._name = name self.points[name] = res return res
[docs] def addDirection(self,name,coordinates=[0,0,0],frame='root'): if name in self.direction: raise ValueError("Direction "+name+" already exists") res = self.direction(coordinates,frame) res._name = name self.directions[name] = res return res
[docs] def addGroup(self,name,group=None,parentFrame='root'): """Adds a subgroup to this group. If parentFrame is given, then the group is attached relative to the given frame. Otherwise, it is assumed attached to the root frame. """ if group==None: group = Group() if name in self.subgroups: raise ValueError("Subgroup "+name+" already exists") group._name = name self.subgroups[name] = group group.frames['root']._parent = self.frame(parentFrame) return group
[docs] def deleteFrame(self,name): """Deletes the named frame. All items that refer to this frame will be automatically converted to be relative to the root coordinate system""" assert name != 'root',"Root frame may not be deleted" if name not in self.frames: raise ValueError("Invalid frame to delete") f = self.frames[name] f._parent = None if f._parent != None: self.childLists[f._parent._name].remove(f) for (n,p) in self.points.items(): if p._parent == f: p._localCoordinates = p.worldCoordinates() p._parent = self.frames['root'] for (n,p) in self.directions.items(): if p._parent == f: p._localCoordinates = p.worldCoordinates() p._parent = self.frames['root'] for c in self.childLists[name]: c._relativeCoordinates = c._worldCoordinates c._parent = self.frames['root'] del self.frames[name] del self.childLists[name]
[docs] def deletePoint(self,name): del self.points[name]
[docs] def deleteDirection(self,name): del self.directions[name]
[docs] def deleteGroup(self,name): del self.subgroups[name]
[docs] def setFrameCoordinates(self,name,coordinates,parent='relative'): """Sets the coordinates of the frame, given as an se3 element. The coordinates can be given either in 'relative' mode, where the coordinates are the natural coordinates of the frame relative to its parent, or in 'world' mode, where the coordinates are the global world coordinates, or they can be given relative to any other frame in this coordinate Group. If None, this defaults to the root frame of this Group.""" f = self.frame(name) if parent==None: parent = 'root' if isinstance(parent,str): if parent=='relative': parent = f._parent elif parent=='world': parent = None else: parent = self.frames[parent] if parent: worldCoordinates = se3.mul(parent._worldCoordinates,coordinates) else: worldCoordinates = coordinates if parent == f._parent: f._relativeCoordinates = coordinates else: f._relativeCoordinates = se3.mul(se3.inv(f._parent._worldCoordinates),worldCoordinates) f._worldCoordinates = worldCoordinates self.updateDependentFrames(f)
[docs] def updateDependentFrames(self,frame): """Whenever Frame's world coordinates are updated, call this to update the downstream frames. This will be called automatically via setFrameCoordinates but not if you change a Frame's coordinates manually.""" for c in self.childLists[frame._name]: c._worldCoordinates = se3.mul(frame.worldCoordinates(),c._relativeCoordinates) self.updateDependentFrames(c)
[docs] def frame(self,name): """Retrieves a named Frame.""" if isinstance(name,Frame): return name try: return self.frames[name] except KeyError: #try looking through groups splits = name.split(":",1) if len(splits)==1: raise ValueError("Frame "+name+" does not exist") if splits[0] not in self.subgroups: raise ValueError("Frame "+name+" or subgroup "+splits[0]+" do not exist") return self.subgroups[splits[0]].frame(splits[1])
[docs] def getPoint(self,name): """Retrieves a named Point.""" if isinstance(name,Point): return name try: return self.points[name] except KeyError: #try looking through groups splits = name.split(":",1) if len(splits)==1: raise ValueError("Point "+name+" does not exist") if splits[0] not in self.subgroups: raise ValueError("Point "+name+" or subgroup "+splits[0]+" do not exist") return self.subgroups[splits[0]].getPoint(splits[1])
[docs] def getDirection(self,name): """Retrieves a named Direction.""" if isinstance(name,Direction): return name try: return self.directions[name] except KeyError: #try looking through groups splits = name.split(":",1) if len(splits)==1: raise ValueError("Direction "+name+" does not exist") if splits[0] not in self.subgroups: raise ValueError("Direction "+name+" or subgroup "+splits[0]+" do not exist") return self.subgroups[splits[0]].getDirection(splits[1])
[docs] def toWorld(self,object): """Converts a Transform, Point, or Direction to have coordinates relative to the world frame.""" return object.toWorld()
[docs] def to(self,object,frame): """Converts a Transform, Point, or Direction to have coordinates relative to the given frame 'frame'.""" return object.to(self.frame(frame))
[docs] def transform(self,sourceFrame,destFrame='root'): """Makes a Transform object from the source frame to the destination frame. """ return Transform(self.frame(sourceFrame),self.frame(destFrame))
[docs] def point(self,coordinates=[0,0,0],frame='root'): """Makes a Point object with the given local coordinates in the given frame. Does not add it to the list of managed points.""" return Point(coordinates,self.frame(frame))
[docs] def direction(self,coordinates=[0,0,0],frame='root'): """Makes a Direction object with the given local coordinates in the given frame. Does not add it to the list of managed points.""" return Direction(coordinates,self.frame(frame))
[docs] def pointFromWorld(self,worldCoordinates=[0,0,0],frame='root'): """Alias for to(point(worldCoordinates,'root'),frame)""" f = self.frame(frame) local = se3.apply(se3.inv(f._worldCoordinates),worldCoordinates) return Point(local,f)
[docs] def directionFromWorld(self,worldCoordinates=[0,0,0],frame='world'): """Alias for to(direction(worldCoordinates,'root'),frame)""" f = self.frame(frame) local = so3.apply(so3.inv(f._worldCoordinates[0]),worldCoordinates) return Direction(local,f)
[docs] def listFrames(self,indent=0): """Prints all the frames in this group and subgroups""" for k,f in self.frames.items(): if indent > 0: print(" "*(indent-1), end=' ') if f._parent == None: print(k) else: print(k,"(%s)"%(f._parent._name,)) for n,g in self.subgroups.items(): if indent > 0: print(" "*(indent-1), end=' ') print(n,":") g.listFrames(indent+2)
[docs] def listItems(self,indent=0): """Prints all the items in this group""" if len(self.frames) > 0: if indent > 0: print(" "*(indent-1), end=' ') print("Frames:") for k,f in self.frames.items(): if indent > 0: print(" "*(indent+1), end=' ') if f._parent == None: print(k) else: print(k,"(%s)"%(f._parent._name,)) if len(self.points) > 0: if indent > 0: print(" "*(indent-1), end=' ') print("Points:") for k in self.points.keys(): if indent > 0: print(" "*(indent+1), end=' ') print(k) if len(self.directions) > 0: if indent > 0: print(" "*(indent-1), end=' ') print("Directions:") for k in self.directions.keys(): if indent > 0: print(" "*(indent+1), end=' ') print(k) if len(self.subgroups) > 0: if indent > 0: print(" "*(indent-1), end=' ') print("Subgroups:") for n,g in self.subgroups.items(): if indent > 0: print(" "*(indent+1), end=' ') print(n,":") g.listItems(indent+2)
[docs]class Manager(Group): """A manager of coordinate frames.""" def __init__(self): Group.__init__(self) self._name = "world_group" self.frames['world'] = self.frames['root']
[docs] def worldFrame(self) -> Frame: return self.frames.get('world',None)
[docs] def destroy(self): Group.destroy(self)
[docs] def deleteFrame(self,name : str): assert name != 'world',"World frame may not be deleted"
[docs] def setFrameCoordinates(self, name : str, coordinates, parent='relative'): assert name != 'world',"World frame must stay fixed at identity" Group.setFrameCoordinates(self,name,coordinates,parent)
#create defaults so you can just call coordinates.addFrame() etc. _defaultManager = Manager() def _callfn(name): global _defaultManager return lambda *args,**kwargs:getattr(_defaultManager,name)(*args,**kwargs)
[docs]def manager() -> Manager: """Retrieves the default top-level manager""" global _defaultManager return _defaultManager
[docs]def setManager(manager : Manager) -> None: """Sets the new top-level manager to a new Manager instance, and returns the old top-level manager.""" assert isinstance(manager,Manager),"setManager must be called with a Manager instance" global _defaultManager res = _defaultManager _defaultManager = manager return res
destroy = _callfn("destroy") setWorldModel = _callfn("setWorldModel") setRobotModel = _callfn("setRobotModel") setController = _callfn("setController") setSimBody = _callfn("setSimBody") updateFromWorld = _callfn("updateFromWorld") updateToWorld = _callfn("updateToWorld") addFrame = _callfn("addFrame") addPoint = _callfn("addPoint") addDirection = _callfn("addDirection") addGroup = _callfn("addGroup") deleteFrame = _callfn("deleteFrame") deletePoint = _callfn("deletePoint") deleteDirection = _callfn("deleteDirection") deleteGroup = _callfn("deleteGroup") setFrameCoordinates = _callfn("setFrameCoordinates") frame = _callfn("frame") getPoint = _callfn("getPoint") getDirection = _callfn("getDirection") toWorld = _callfn("toWorld") to = _callfn("to") transform = _callfn("transform") point = _callfn("point") direction = _callfn("direction") pointFromWorld = _callfn("pointFromWorld") directionFromWorld = _callfn("directionFromWorld") listFrames = _callfn("listFrames") listItems = _callfn("listItems") def _ancestor_with_link(frame): """Returns the nearest ancestor of the given frame attached to a robot link or rigid object""" while frame and (frame._data == None or not isinstance(frame._data,(RobotModelLink,RigidObjectModel))): frame = frame._parent return frame
[docs]def ik_objective(obj,target) -> IKObjective: """Returns an IK objective that attempts to fix the given klampt.coordinates object 'obj' at given target object 'target'. Arguments: obj: An instance of one of the {Point,Direction,Transform,Frame} classes. target: If 'obj' is a Point, Direction, or Frame objects, this must be an object of the same type of 'obj' denoting the target to which 'obj' should be fixed. In other words, the local coordinates of 'obj' relative to 'target's parent frame will be equal to 'target's local coordinates. If obj is a Transform object, this element is an se3 object. Returns: An IK objective to be used with the klampt.ik module. Since the klampt.ik module is not aware about custom frames, an ancestor of the object must be attached to a RobotModelLink or a RigidObjectModel, or else None will be returned. The same goes for target, if provided. TODO: support lists of objects to fix. TODO: support Direction constraints. """ body = None coords = None ref = None if isinstance(obj,Frame): assert isinstance(target,Frame),"ik_objective: target must be of same type as obj" body = obj ref = target.parent() coords = target.relativeCoordinates() elif isinstance(obj,Transform): if ref != None: print("ik_objective: Warning, ref argument passed with Transform object, ignoring") body = obj.source() ref = obj.destination() coords = target elif isinstance(obj,(Point,Direction)): assert type(target)==type(obj),"ik_objective: target must be of same type as obj" body = obj.frame() ref = target.frame() coords = target.localCoordinates() else: raise ValueError("Argument to ik_objective must be an object from the coordinates module") linkframe = _ancestor_with_link(body) if linkframe == None: print("Warning: object provided to ik_objective is not attached to a robot link or rigid object, returning None") return None linkbody = linkframe._data #find the movable frame attached to ref refframe = _ancestor_with_link(ref) if ref != None else None refbody = (refframe._data if refframe!=None else None) if isinstance(obj,(Frame,Transform)): #figure out the desired transform T[linkbody->refbody], given #coords = T[obj->ref], T[obj->linkbody], T[ref->refbody] #result = (T[ref->refbody] * coords * T[obj->linkbody]^-1) if linkframe != body: coords = se3.mul(coords,Transform(linkframe,body).coordinates()) if refframe != ref: coords = se3.mul(Transform(ref,refframe).coordinates(),coords) return ik.objective(linkbody,ref=refbody,R=coords[0],t=coords[1]) elif isinstance(obj,Point): #figure out the local and world points local = obj.to(linkframe).localCoordinates() world = target.to(refframe).localCoordinates() return ik.objective(linkbody,local=[local],world=[world]) elif isinstance(obj,Direction): raise ValueError("Axis constraints are not yet supported in the klampt.ik module") return None
[docs]def ik_fixed_objective(obj,ref=None): """Returns an IK objective that attempts to fix the given klampt.coordinates object at its current pose. If ref=None, its pose is fixed in world coordinates. Otherwise, its pose is fixed relative to the reference frame ref. Arguments: obj: An instance of one of the {Point,Direction,Transform,Frame} classes. ref (optional): either None, or a Frame object denoting the reference frame to which the object should be fixed. (If obj is a Transform object, its destination frame is used as the reference frame, and this argument is ignored.) Returns: IKObjective: An IK objective to be used with the klampt.ik module. For Point, Direction, and Frame objects this objective fixes the object coordinates relative to the ref frame, or the world if None frame is provided. For Transform objects the source frame is fixed relative to the destination frame. Since the klampt.ik module is not aware about custom frames, an ancestor of the object must be attached to a RobotModelLink or a RigidObjectModel, or else None will be returned. The same goes for ref, if provided. TODO: support lists of objects to fix. TODO: support Direction constraints. """ if isinstance(obj,(Point,Direction)): return ik_objective(obj,obj.to(ref)) elif isinstance(obj,Frame): return ik_fixed_objective(Transform(obj,ref)) elif isinstance(obj,Transform): if ref != None: print("ik_fixed_objective: Warning, ref argument passed with Transform object, ignoring") return ik_objective(obj,obj.coordinates()) else: raise ValueError("Argument to ik_fixed_objective must be an object from the coordinates module")