摘要：
3floatcosHalfTheta=a.x*b.x+a.y*b.y+a.z*b.z+a.w*b.w；0.0F）｛5b=新四元数（b）；7b.x=-b.x；9b.z=-b.z；0.001D）｛18floatoneOverSinHalfTheta=1.0F/sinHalfTheta；
ARCore中四元数差值算法：
其中t的取值范围为[0, 1]，当 t = 0 时，结果为a；当t = 1 时，结果为b。
1 public static Quaternion makeInterpolated(Quaternion a, Quaternion b, float t) { 2 Quaternion out = new Quaternion(); 3 float cosHalfTheta = a.x * b.x + a.y * b.y + a.z * b.z + a.w * b.w; 4 if(cosHalfTheta < 0.0F) { 5 b = new Quaternion(b); 6 cosHalfTheta = -cosHalfTheta; 7 b.x = -b.x; 8 b.y = -b.y; 9 b.z = -b.z; 10 b.w = -b.w; 11 } 12 13 float halfTheta = (float)Math.acos((double)cosHalfTheta); 14 float sinHalfTheta = (float)Math.sqrt((double)(1.0F - cosHalfTheta * cosHalfTheta)); 15 float ratioA; 16 float ratioB; 17 if((double)Math.abs(sinHalfTheta) > 0.001D) { 18 float oneOverSinHalfTheta = 1.0F / sinHalfTheta; 19 ratioA = (float)Math.sin((double)((1.0F - t) * halfTheta)) * oneOverSinHalfTheta; 20 ratioB = (float)Math.sin((double)(t * halfTheta)) * oneOverSinHalfTheta; 21 } else { 22 ratioA = 1.0F - t; 23 ratioB = t; 24 } 25 26 out.x = ratioA * a.x + ratioB * b.x; 27 out.y = ratioA * a.y + ratioB * b.y; 28 out.z = ratioA * a.z + ratioB * b.z; 29 out.w = ratioA * a.w + ratioB * b.w; 30 out.normalizeInPlace(); 31 return out; 32 }