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#include "primitives/Bend.hpp" |
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namespace oopse { |
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/**@todo still a lot left to improve*/ |
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void Bend::calcForce() { |
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Vector3d pos1 = atom1_->getPos(); |
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Vector3d pos2 = atom2_->getPos(); |
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Vector3d pos3 = atom3_->getPos(); |
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Vector3d r21 = pos1 - pos2; |
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double d21 = r21.length(); |
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double d21inv = 1.0 / d21; |
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Vector3d r23 = pos3 - pos2; |
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double d23 = r23.length(); |
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double d23inv = 1.0 / d23; |
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double cosTheta = dot(r21, r23) / (d21 * d23); |
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//check roundoff |
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if (cosTheta > 1.0) { |
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cosTheta = 1.0; |
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} else if (cosTheta < -1.0) { |
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cosTheta = -1.0; |
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} |
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double theta = acos(cosTheta); |
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double dVdTheta; |
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bendType_->calcForce(theta, potential_, dVdTheta); |
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double sinTheta = sqrt(1.0 - cosTheta * cosTheta); |
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if (fabs(sinTheta) < 1.0E-6) { |
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sinTheta = 1.0E-6; |
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} |
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double commonFactor1 = dVdTheta / sinTheta * d21inv; |
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double commonFactor2 = dVdTheta / sinTheta * d23inv; |
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Vector3d force1 = commonFactor1 * (r23 * d23inv - r21*d21inv*cosTheta); |
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Vector3d force3 = commonFactor2 * (r21 * d21inv - r23*d23inv*cosTheta); |
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//total force in current bend is zero |
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Vector3d force2 = force1 + force3; |
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force2 *= -1.0; |
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atom1_->addFrc(force1); |
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atom2_->addFrc(force2); |
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atom3_->addFrc(force3); |
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} |
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} //end namespace oopse |
