void MeshMassPropertiesTests::testBoxAsMesh() {
// verify that a mesh box produces the same mass properties as the analytic box.
// build a box:
// /
// y
// /
// 6-------------------------7
// /| /|
// / | / |
// / 2----------------------/--3
// / / / /
// | 4-------------------------5 / --x--
// z | / | /
// | |/ |/
// 0 ------------------------1
btScalar x(5.0f);
btScalar y(3.0f);
btScalar z(2.0f);
VectorOfPoints points;
points.reserve(8);
points.push_back(btVector3(0.0f, 0.0f, 0.0f));
points.push_back(btVector3(x, 0.0f, 0.0f));
points.push_back(btVector3(0.0f, y, 0.0f));
points.push_back(btVector3(x, y, 0.0f));
points.push_back(btVector3(0.0f, 0.0f, z));
points.push_back(btVector3(x, 0.0f, z));
points.push_back(btVector3(0.0f, y, z));
points.push_back(btVector3(x, y, z));
VectorOfIndices triangles;
pushTriangle(triangles, 0, 1, 4);
pushTriangle(triangles, 1, 5, 4);
pushTriangle(triangles, 1, 3, 5);
pushTriangle(triangles, 3, 7, 5);
pushTriangle(triangles, 2, 0, 6);
pushTriangle(triangles, 0, 4, 6);
pushTriangle(triangles, 3, 2, 7);
pushTriangle(triangles, 2, 6, 7);
pushTriangle(triangles, 4, 5, 6);
pushTriangle(triangles, 5, 7, 6);
pushTriangle(triangles, 0, 2, 1);
pushTriangle(triangles, 2, 3, 1);
// compute expected mass properties analytically
btVector3 expectedCenterOfMass = 0.5f * btVector3(x, y, z);
btScalar expectedVolume = x * y * z;
btMatrix3x3 expectedInertia;
computeBoxInertia(expectedVolume, btVector3(x, y, z), expectedInertia);
// compute the mass properties using the mesh
MeshMassProperties mesh(points, triangles);
// verify
QCOMPARE_WITH_ABS_ERROR(mesh._volume, expectedVolume, acceptableRelativeError * expectedVolume);
QCOMPARE_WITH_ABS_ERROR(mesh._centerOfMass, expectedCenterOfMass, acceptableAbsoluteError);
// test this twice: _RELATIVE_ERROR doesn't test zero cases (to avoid divide-by-zero); _ABS_ERROR does.
QCOMPARE_WITH_ABS_ERROR(mesh._inertia, expectedInertia, acceptableAbsoluteError);
QCOMPARE_WITH_RELATIVE_ERROR(mesh._inertia, expectedInertia, acceptableRelativeError);
// These two macros impl this:
// for (int i = 0; i < 3; ++i) {
// for (int j = 0; j < 3; ++j) {
// if (expectedInertia [i][j] == btScalar(0.0f)) {
// error = mesh._inertia[i][j] - expectedInertia[i][j]; // COMPARE_WITH_ABS_ERROR
// if (fabsf(error) > acceptableAbsoluteError) {
// std::cout << __FILE__ << ":" << __LINE__ << " ERROR : inertia[" << i << "][" << j << "] off by "
// << error << " absolute"<< std::endl;
// }
// } else {
// error = (mesh._inertia[i][j] - expectedInertia[i][j]) / expectedInertia[i][j]; // COMPARE_WITH_RELATIVE_ERROR
// if (fabsf(error) > acceptableRelativeError) {
// std::cout << __FILE__ << ":" << __LINE__ << " ERROR : inertia[" << i << "][" << j << "] off by "
// << error << std::endl;
// }
// }
// }
// }
}
