47 lines
No EOL
1.8 KiB
Text
47 lines
No EOL
1.8 KiB
Text
/*
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contributors: Patricio Gonzalez Vivo
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description: |
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Linear interpolation between two quaternions.
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This function is based on the implementation of slerp() found inthe GLM library.
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use: <QUAT> quatLerp(<QUAT> a, <QUAT> b, <float> t)
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license:
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- Copyright (c) 2021 Patricio Gonzalez Vivo under Prosperity License - https://prosperitylicense.com/versions/3.0.0
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- Copyright (c) 2021 Patricio Gonzalez Vivo under Patron License - https://lygia.xyz/license
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*/
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#ifndef FNC_QUATLERP
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#define FNC_QUATLERP
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QUAT quatLerp(QUAT qa, QUAT qb, float t) {
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// qa = normalize(qa);
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// qb = normalize(qb);
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// Calculate angle between them.
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float cosHalfTheta = qa.w * qb.w + dot(qa.xyz, qb.xyz);
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// avoid taking the longer way: choose one representation
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qb = (cosHalfTheta < 0.0)? -qb : qb;
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// qb = (cosHalfTheta < 0.0)? quatNeg(qb) : qb;
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cosHalfTheta = (cosHalfTheta < 0.0)? -cosHalfTheta : cosHalfTheta;
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// if qa = qb or qa = -qb then theta = 0 and we can return qa
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if (abs(cosHalfTheta) >= 1.0) // greater-sign necessary for numerical stability
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return qa;
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// Calculate temporary values.
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float halfTheta = acos(cosHalfTheta);
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float sinHalfTheta = sqrt(1.0 - cosHalfTheta * cosHalfTheta); // NOTE: we checked above that |cosHalfTheta| < 1
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// if theta = pi then result is not fully defined
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// we could rotate around any axis normal to qa or qb
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if (abs(sinHalfTheta) < 0.001/*some epsilon*/)
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// return quatAdd( quatMul(qa, 0.5), quatMul(qb, 0.5));
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return normalize( qa * 0.5 + qb * 0.5 );
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float ratioA = sin((1.0 - t) * halfTheta) / sinHalfTheta;
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float ratioB = sin(t * halfTheta) / sinHalfTheta;
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// return quatNorm( quatAdd( quatMul(qa, ratioA), quatMul(qb, ratioB)) );
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return normalize( qa * ratioA + qb * ratioB );
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}
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#endif |