Talk:LlAngleBetween

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.x + b.y * b.y + b.z * 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)