# Talk:LlAngleBetween

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## LSO Optimized Reference Impelementation

This version of the latest reference implementation is optimized for LSO bytecode. Execution speed should be about the same.

<lsl>float AngleBetween(rotation a, rotation b)//more complex implementation but more accurate, and reasonably fast. {

b /= a; // calculate the rotation between the two arguments as quaternion float s2 = b.s * b.s; // square of the s-element float v2 = <b.x, b.y, b.z> * <b.x, b.y, b.z>; // sum of the squares of the v-elements

//we bulk all our returns into a single return because returning requires several bytecodes. //specifically the local variables and parameters must be popped off the stack.

if (s2 < v2) // compare the s-component to the v-component v2 = llAcos(llSqrt(s2 / (s2 + v2))); // use arccos if the v-component is dominant else if (v2) // make sure the v-component is non-zero v2 = llAsin(llSqrt(v2 / (s2 + v2))); // use arcsin if the s-component is dominant

//if one or both arguments are scaled too small to be meaningful v2 is zero, or the values are the same, v2 is zero. //in that case we want to return zero so multiplying v2 by 2.0 will have no effect on the value returned. return v2 * 2.0;

}//Written by Moon Metty & Miranda Umino. Optimizations by Strife Onizuka</lsl>

-- **Strife** ^{(talk|contribs)} 09:48, 2 September 2012 (PDT)