Code:

pWorld->getSolverInfo().m_solverMode |= SOLVER_DISABLE_VELOCITY_DEPENDENT_FRICTION_DIRECTION ;

Code:

auto[direction, desired_speed] = ...// In case it helps, note that soft body friction is controlled via the softBody->m_cfg.kDF parameter (0 = no friction, 1 = max):// http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?t=6730// m_lateralFrictionDir1 is in local coordinatesauto proposed_lateral_friction_dir1 = beltBody.getWorldTransform().getBasis() * direction;auto proposed_lateral_friction_dir2 = proposed_lateral_friction_dir1.cross(cp.m_normalWorldOnB);// we should normalize dir2, but only if possiblebtScalar l2 = proposed_lateral_friction_dir2.length2();if (l2 >= SIMD_EPSILON * SIMD_EPSILON){// yes: this is now normalized!proposed_lateral_friction_dir2 /= btSqrt(l2);cp.m_lateralFrictionDir1 = std::move(proposed_lateral_friction_dir1);cp.m_contactMotion1 = desired_speed;// This is needed together with SOLVER_USE_2_FRICTION_DIRECTIONS// m_lateralFrictionDir2 should always be perpendicular to m_lateralFrictionDir1cp.m_lateralFrictionDir2 = std::move(proposed_lateral_friction_dir2);cp.m_combinedFriction = ...if (not body.isActive())body.activate();cp.m_contactPointFlags |= BT_CONTACT_FLAG_LATERAL_FRICTION_INITIALIZED;}