💿🐜 Antkeeper source code
https://antkeeper.com
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53 lines
2.0 KiB
53 lines
2.0 KiB
/*
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* Copyright (C) 2023 Christopher J. Howard
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*
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* This file is part of Antkeeper source code.
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*
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* Antkeeper source code is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Antkeeper source code is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <engine/physics/kinematics/constraints/spring-constraint.hpp>
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namespace physics {
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void spring_constraint::solve(float dt)
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{
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if (!m_body_a || !m_body_b)
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{
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return;
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}
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// Get radius vectors from centers of mass to spring attachment points
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const math::fvec3 radius_a = m_body_a->get_orientation() * m_point_a;
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const math::fvec3 radius_b = m_body_b->get_orientation() * m_point_b;
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// Get world-space spring attachment points
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const math::fvec3 point_a = m_body_a->get_position() + radius_a;
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const math::fvec3 point_b = m_body_b->get_position() + radius_b;
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// Calculate relative velocity between the attachment points
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const math::fvec3 velocity = m_body_b->get_point_velocity(radius_b) - m_body_a->get_point_velocity(radius_a);
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// Calculate spring force
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// F = -k * (|x| - d) * (x / |x|) - bv
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const math::fvec3 difference = point_b - point_a;
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const float distance = std::sqrt(math::dot(difference, difference));
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const math::fvec3 force = -m_stiffness * (distance - m_resting_length) * (difference / distance) - velocity * m_damping;
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// Apply spring force to bodies at attachment points
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m_body_a->apply_force(-force, radius_a);
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m_body_b->apply_force(force, radius_b);
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}
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} // namespace physics
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