StateSampling.py

#!/usr/bin/env python

######################################################################
# Software License Agreement (BSD License)
#
#  Copyright (c) 2010, Rice University
#  All rights reserved.
#
#  Redistribution and use in source and binary forms, with or without
#  modification, are permitted provided that the following conditions
#  are met:
#
#   * Redistributions of source code must retain the above copyright
#     notice, this list of conditions and the following disclaimer.
#   * Redistributions in binary form must reproduce the above
#     copyright notice, this list of conditions and the following
#     disclaimer in the documentation and/or other materials provided
#     with the distribution.
#   * Neither the name of the Rice University nor the names of its
#     contributors may be used to endorse or promote products derived
#     from this software without specific prior written permission.
#
#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
#  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
#  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
#  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
#  COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
#  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
#  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
#  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
#  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
#  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
#  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
#  POSSIBILITY OF SUCH DAMAGE.
######################################################################

# Author: Mark Moll

try:
    from ompl import util as ou
    from ompl import base as ob
    from ompl import geometric as og
except:
    # if the ompl module is not in the PYTHONPATH assume it is installed in a
    # subdirectory of the parent directory called "py-bindings."
    from os.path import abspath, dirname, join
    import sys
    sys.path.insert(0, join(dirname(dirname(abspath(__file__))),'py-bindings'))
    from ompl import util as ou
    from ompl import base as ob
    from ompl import geometric as og
from time import sleep
from math import fabs

## @cond IGNORE

# This is a problem-specific sampler that automatically generates valid
# states; it doesn't need to call SpaceInformation::isValid. This is an
# example of constrained sampling. If you can explicitly describe the set valid
# states and can draw samples from it, then this is typically much more
# efficient than generating random samples from the entire state space and
# checking for validity.
class MyValidStateSampler(ob.ValidStateSampler):
    def __init__(self, si):
        super(MyValidStateSampler, self).__init__(si)
        self.name_ = "my sampler"
        self.rng_ = ou.RNG()

    # Generate a sample in the valid part of the R^3 state space.
    # Valid states satisfy the following constraints:
    # -1<= x,y,z <=1
    # if .25 <= z <= .5, then |x|>.8 and |y|>.8
    def sample(self, state):
        z = self.rng_.uniformReal(-1,1)

        if z>.25 and z<.5:
            x = self.rng_.uniformReal(0,1.8)
            y = self.rng_.uniformReal(0,.2)
            i = self.rng_.uniformInt(0,3)
            if i==0:
                state[0]=x-1
                state[1]=y-1
            elif i==1:
                state[0]=x-.8
                state[1]=y+.8
            elif i==2:
                state[0]=y-1
                state[1]=x-1
            elif i==3:
                state[0]=y+.8
                state[1]=x-.8
        else:
            state[0] = self.rng_.uniformReal(-1,1)
            state[1] = self.rng_.uniformReal(-1,1)
        state[2] = z
        return True

## @endcond

# This function is needed, even when we can write a sampler like the one
# above, because we need to check path segments for validity
def isStateValid(state):
    # Let's pretend that the validity check is computationally relatively
    # expensive to emphasize the benefit of explicitly generating valid
    # samples
    sleep(.001)
    # Valid states satisfy the following constraints:
    # -1<= x,y,z <=1
    # if .25 <= z <= .5, then |x|>.8 and |y|>.8
    return not (fabs(state[0]<.8) and fabs(state[1]<.8) and
        state[2]>.25 and state[2]<.5)

# return an obstacle-based sampler
def allocOBValidStateSampler(si):
    # we can perform any additional setup / configuration of a sampler here,
    # but there is nothing to tweak in case of the ObstacleBasedValidStateSampler.
    return ob.ObstacleBasedValidStateSampler(si)

# return an instance of my sampler
def allocMyValidStateSampler(si):
    return MyValidStateSampler(si)

def plan(samplerIndex):
    # construct the state space we are planning in
    space = ob.RealVectorStateSpace(3)

    # set the bounds
    bounds = ob.RealVectorBounds(3)
    bounds.setLow(-1)
    bounds.setHigh(1)
    space.setBounds(bounds)

    # define a simple setup class
    ss = og.SimpleSetup(space)

    # set state validity checking for this space
    ss.setStateValidityChecker(ob.StateValidityCheckerFn(isStateValid))

    # create a start state
    start = ob.State(space)
    start[0] = 0
    start[1] = 0
    start[2] = 0

    # create a goal state
    goal = ob.State(space)
    goal[0] = 0
    goal[1] = 0
    goal[2] = 1

    # set the start and goal states;
    ss.setStartAndGoalStates(start, goal)

    # set sampler (optional; the default is uniform sampling)
    si = ss.getSpaceInformation()
    if samplerIndex==1:
        # use obstacle-based sampling
        si.setValidStateSamplerAllocator(ob.ValidStateSamplerAllocator(allocOBValidStateSampler))
    elif samplerIndex==2:
        # use my sampler
        si.setValidStateSamplerAllocator(ob.ValidStateSamplerAllocator(allocMyValidStateSampler))

    # create a planner for the defined space
    planner = og.PRM(si)
    ss.setPlanner(planner)

    # attempt to solve the problem within ten seconds of planning time
    solved = ss.solve(10.0)
    if (solved):
        print("Found solution:")
        # print the path to screen
        print(ss.getSolutionPath())
    else:
        print("No solution found")


if __name__ == '__main__':
    print("Using default uniform sampler:")
    plan(0)
    print("\nUsing obstacle-based sampler:")
    plan(1)
    print("\nUsing my sampler:")
    plan(2)