test_fcl_sphere_box.cpp

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#include <memory>

#include <gtest/gtest.h>
#include <Eigen/Dense>

#include "eigen_matrix_compare.h"
#include "fcl/narrowphase/collision_object.h"
#include "fcl/narrowphase/distance.h"

// TODO(SeanCurtis-TRI): Modify this test so it can be re-used for the distance
// query -- such that the sphere is slightly separated instead of slightly
// penetrating.  See test_sphere_box.cpp for an example.

// This collides a box with a sphere. The box is long and skinny with size
// (w, d, h) and its geometric frame is aligned with the world frame.
// The sphere has radius r and is positioned at (sx, sy, sz) with an identity
// orientation. In this configuration, the sphere penetrates the box slightly
// on its face that faces in the +z direction. The contact is *fully* contained
// in that face. (As illustrated below.)
//
// Side view
//                     z        small sphere
//                     ┆            ↓
// ┏━━━━━━━━━━━━━━━━━━━┿━━━━━━━━━━━━◯━━━━━━┓      ┬
// ╂┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┼┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄╂  x   h
// ┗━━━━━━━━━━━━━━━━━━━┿━━━━━━━━━━━━━━━━━━━┛      ┴
//                     ┆
//
// ├────────────────── w ──────────────────┤
//
// Top view
//                     y        small sphere
//                     ┆            ↓
// ┏━━━━━━━━━━━━━━━━━━━┿━━━━━━━━━━━━━━━━━━━┓      ┬
// ╂┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┼┄┄┄┄┄┄┄┄┄┄┄┄◯┄┄┄┄┄┄╂  x   d
// ┗━━━━━━━━━━━━━━━━━━━┿━━━━━━━━━━━━━━━━━━━┛      ┴
//                     ┆
//
// Properties of expected outcome:
//  - One contact *should* be reported,
//  - Penetration depth δ should be: radius - (sz - h / 2),
//  - Contact point should be at: [sx, sy, h / 2 - δ / 2], and
//  - Contact normal should be [0, 0, -1] (pointing from sphere into box).
//
// NOTE: Orientation of the sphere should *not* make a difference and is not
// tested here; it relies on the sphere-box primitive algorithm unit tests to
// have robustly tested that.
//
// This test *fails* if GJK is used to evaluate the collision. It passes if the
// custom sphere-box algorithm is used, and, therefore, its purpose is to
// confirm that the custom algorithm is being applied. It doesn't exhaustively
// test sphere-box collision. It merely confirms the tested primitive algorithm
// has been wired up correctly.
template <typename S>
void LargeBoxSmallSphereTest(fcl::GJKSolverType solver_type) {
  using fcl::Vector3;
  using Real = typename fcl::constants<S>::Real;
  const Real eps = fcl::constants<S>::eps();

  // Configure geometry.

  // Box and sphere dimensions.
  const Real w = 0.115;
  const Real h = 0.0025;
  const Real d = 0.01;
  // The magnitude of the box's extents along each axis.
  const Vector3<S> half_size{w / 2, d / 2, h / 2};
  const Real r = 0.0015;
  auto sphere_geometry = std::make_shared<fcl::Sphere<S>>(r);
  auto box_geometry = std::make_shared<fcl::Box<S>>(w, d, h);

  // Poses of the geometry.
  fcl::Transform3<S> X_WB = fcl::Transform3<S>::Identity();

  // Compute multiple sphere locations. All at the same height to produce a
  // fixed, expected penetration depth of half of its radius. The reported
  // position of the contact will have the x- and y- values of the sphere
  // center, but be half the target_depth below the +z face, i.e.,
  //  pz = (h / 2) - (target_depth / 2)
  const Real target_depth = r * 0.5;
  // Sphere center's height (position in z).
  const Real sz = h / 2 + r - target_depth;
  const Real pz = h / 2 - target_depth / 2;
  // This transform will get repeated modified in the nested for loop below.
  fcl::Transform3<S> X_WS = fcl::Transform3<S>::Identity();

  fcl::CollisionObject<S> sphere(sphere_geometry, X_WS);
  fcl::CollisionObject<S> box(box_geometry, X_WB);

  // Expected results. (Expected position is defined inside the for loop as it
  // changes with each new position of the sphere.)
  const S expected_depth = target_depth;
  // This normal direction assumes the *sphere* is the first collision object.
  // If the order is reversed, the normal must be likewise reversed.
  const Vector3<S> expected_normal = -Vector3<S>::UnitZ();

  // Set up the collision request.
  fcl::CollisionRequest<S> collision_request(1 /* num contacts */,
                                             true /* enable_contact */);
  collision_request.gjk_solver_type = solver_type;

  // Sample around the surface of the +z face on the box for a fixed penetration
  // depth. Note: the +z face extends in the +/- x and y directions up to the
  // distance half_size. Notes on the selected samples:
  //  - We've picked positions such that the *whole* sphere projects onto the
  //    +z face (e.g., half_size(i) - r). This *guarantees* that the contact is
  //    completely contained in the +z face so there is no possible ambiguity
  //    in the results.
  //  - We've picked points out near the boundaries, in the middle, and *near*
  //    zero without being zero. The GJK algorithm can actually provide the
  //    correct result at the (eps, eps) sample points. We leave those sample
  //    points in to confirm no degradation.
  const std::vector<Real> x_values{
      -half_size(0) + r,  -half_size(0) * S(0.5), -eps, 0, eps,
      half_size(0) * S(0.5), half_size(0) - r};
  const std::vector<Real> y_values{
      -half_size(1) + r,  -half_size(1) * S(0.5), -eps, 0, eps,
      half_size(1) * S(0.5), half_size(1) - r};
  for (Real sx : x_values) {
    for (Real sy : y_values ) {
      // Repose the sphere.
      X_WS.translation() << sx, sy, sz;
      sphere.setTransform(X_WS);

      auto evaluate_collision = [&collision_request, &X_WS](
          const fcl::CollisionObject<S>* s1, const fcl::CollisionObject<S>* s2,
          S expected_depth, const Vector3<S>& expected_normal,
          const Vector3<S>& expected_pos, Real eps) {
        // Compute collision.
        fcl::CollisionResult<S> collision_result;
        std::size_t contact_count =
            fcl::collide(s1, s2, collision_request, collision_result);

        // Test answers
        if (contact_count == collision_request.num_max_contacts) {
          std::vector<fcl::Contact<S>> contacts;
          collision_result.getContacts(contacts);
          GTEST_ASSERT_EQ(contacts.size(), collision_request.num_max_contacts);

          const fcl::Contact<S>& contact = contacts[0];
          EXPECT_NEAR(contact.penetration_depth, expected_depth, eps)
                    << "Sphere at: " << X_WS.translation().transpose();
          EXPECT_TRUE(fcl::CompareMatrices(contact.normal,
                                           expected_normal,
                                           eps,
                                           fcl::MatrixCompareType::absolute))
                    << "Sphere at: " << X_WS.translation().transpose();
          EXPECT_TRUE(fcl::CompareMatrices(
              contact.pos, expected_pos, eps, fcl::MatrixCompareType::absolute))
                    << "Sphere at: " << X_WS.translation().transpose();
        } else {
          EXPECT_TRUE(false) << "No contacts reported for sphere at: "
                             << X_WS.translation().transpose();
        }
      };

      Vector3<S> expected_pos{sx, sy, pz};
      evaluate_collision(&sphere, &box, expected_depth, expected_normal,
                         expected_pos, eps);
      evaluate_collision(&box, &sphere, expected_depth, -expected_normal,
                         expected_pos, eps);
    }
  }
}

GTEST_TEST(FCL_SPHERE_BOX, LargBoxSmallSphere_ccd) {
  LargeBoxSmallSphereTest<double>(fcl::GJKSolverType::GST_LIBCCD);
  LargeBoxSmallSphereTest<float>(fcl::GJKSolverType::GST_LIBCCD);
}

GTEST_TEST(FCL_SPHERE_BOX, LargBoxSmallSphere_indep) {
  LargeBoxSmallSphereTest<double>(fcl::GJKSolverType::GST_INDEP);
  LargeBoxSmallSphereTest<float>(fcl::GJKSolverType::GST_INDEP);
}

//==============================================================================
int main(int argc, char* argv[]) {
  ::testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
}