src/distance/capsule_capsule.cpp

Go to the documentation of this file.

/*
 * Software License Agreement (BSD License)
 *  Copyright (c) 2015-2021, CNRS-LAAS INRIA
 *  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 Open Source Robotics Foundation 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.
 */
 
#include "coal/math/transform.h"
#include "coal/shape/geometric_shapes.h"
#include "coal/internal/shape_shape_func.h"
 
// Note that partial specialization of template functions is not allowed.
// Therefore, two implementations with the default narrow phase solvers are
// provided. If another narrow phase solver were to be used, the default
// template implementation would be called, unless the function is also
// specialized for this new type.
//
// One solution would be to make narrow phase solvers derive from an abstract
// class and specialize the template for this abstract class.
namespace coal {
struct GJKSolver;
 
namespace internal {
CoalScalar clamp(const CoalScalar& num, const CoalScalar& denom) {
  assert(denom >= 0.);
  if (num <= 0.)
    return 0.;
  else if (num >= denom)
    return 1.;
  else
    return num / denom;
}
 
void clamped_linear(Vec3s& a_sd, const Vec3s& a, const CoalScalar& s_n,
                    const CoalScalar& s_d, const Vec3s& d) {
  assert(s_d >= 0.);
  if (s_n <= 0.)
    a_sd = a;
  else if (s_n >= s_d)
    a_sd = a + d;
  else
    a_sd = a + s_n / s_d * d;
}
 
// Compute the distance between C1 and C2 by computing the distance
// between the two segments supporting the capsules.
// Match algorithm of Real-Time Collision Detection, Christer Ericson - Closest
// Point of Two Line Segments
template <>
CoalScalar ShapeShapeDistance<Capsule, Capsule>(
    const CollisionGeometry* o1, const Transform3s& tf1,
    const CollisionGeometry* o2, const Transform3s& tf2, const GJKSolver*,
    const bool, Vec3s& wp1, Vec3s& wp2, Vec3s& normal) {
  const Capsule* capsule1 = static_cast<const Capsule*>(o1);
  const Capsule* capsule2 = static_cast<const Capsule*>(o2);
 
  CoalScalar EPSILON = std::numeric_limits<CoalScalar>::epsilon() * 100;
 
  // We assume that capsules are centered at the origin.
  const coal::Vec3s& c1 = tf1.getTranslation();
  const coal::Vec3s& c2 = tf2.getTranslation();
  // We assume that capsules are oriented along z-axis.
  CoalScalar halfLength1 = capsule1->halfLength;
  CoalScalar halfLength2 = capsule2->halfLength;
  CoalScalar radius1 = (capsule1->radius + capsule1->getSweptSphereRadius());
  CoalScalar radius2 = (capsule2->radius + capsule2->getSweptSphereRadius());
  // direction of capsules
  // ||d1|| = 2 * halfLength1
  const coal::Vec3s d1 = 2 * halfLength1 * tf1.getRotation().col(2);
  const coal::Vec3s d2 = 2 * halfLength2 * tf2.getRotation().col(2);
 
  // Starting point of the segments
  // p1 + d1 is the end point of the segment
  const coal::Vec3s p1 = c1 - d1 / 2;
  const coal::Vec3s p2 = c2 - d2 / 2;
  const coal::Vec3s r = p1 - p2;
  CoalScalar a = d1.dot(d1);
  CoalScalar b = d1.dot(d2);
  CoalScalar c = d1.dot(r);
  CoalScalar e = d2.dot(d2);
  CoalScalar f = d2.dot(r);
  // S1 is parametrized by the equation p1 + s * d1
  // S2 is parametrized by the equation p2 + t * d2
 
  Vec3s w1, w2;
  if (a <= EPSILON) {
    w1 = p1;
    if (e <= EPSILON)
      // Check if the segments degenerate into points
      w2 = p2;
    else
      // First segment is degenerated
      clamped_linear(w2, p2, f, e, d2);
  } else if (e <= EPSILON) {
    // Second segment is degenerated
    clamped_linear(w1, p1, -c, a, d1);
    w2 = p2;
  } else {
    // Always non-negative, equal 0 if the segments are colinear
    CoalScalar denom = fmax(a * e - b * b, 0);
 
    CoalScalar s;
    CoalScalar t;
    if (denom > EPSILON) {
      s = clamp((b * f - c * e), denom);
      t = b * s + f;
    } else {
      s = 0.;
      t = f;
    }
 
    if (t <= 0.0) {
      w2 = p2;
      clamped_linear(w1, p1, -c, a, d1);
    } else if (t >= e) {
      clamped_linear(w1, p1, (b - c), a, d1);
      w2 = p2 + d2;
    } else {
      w1 = p1 + s * d1;
      w2 = p2 + t / e * d2;
    }
  }
 
  // witness points achieving the distance between the two segments
  CoalScalar distance = (w1 - w2).norm();
 
  // capsule spcecific distance computation
  distance = distance - (radius1 + radius2);
 
  // Normal points from o1 to o2
  normal = (w2 - w1).normalized();
  wp1 = w1 + radius1 * normal;
  wp2 = w2 - radius2 * normal;
 
  return distance;
}
}  // namespace internal
 
}  // namespace coal