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 wiki:scripting_portal:lsl_functions:llanglebetween [2018/11/20 17:17]Royale Mobian created wiki:scripting_portal:lsl_functions:llanglebetween [2019/07/19 21:22] (current)Royale Mobian 2019/07/19 21:22 Royale Mobian 2018/11/20 17:17 Royale Mobian created 2019/07/19 21:22 Royale Mobian 2018/11/20 17:17 Royale Mobian created Line 1: Line 1: ====== llAngleBetween ====== ====== llAngleBetween ====== - ===== Introduction ===== + **[[wiki:​scripting_portal:​lsl_functions|Function]]:​ [[wiki:​scripting_portal:​lsl_types:​float|float]] llAngleBetween( [[wiki:​scripting_portal:​lsl_types:​rotation|rotation]] a, [[wiki:​scripting_portal:​lsl_types:​rotation|rotation]] b );** + Returns a float that is the angle in radians between rotation **a** and rotation **b**. + * rotation a – start rotation + * rotation b – end rotation + ===== Examples ===== + + default + { + touch_start(integer num_detected) + { + rotation currentRootRotation = llGetRootRotation();​ + float angle = llAngleBetween(ZERO_ROTATION,​ currentRootRotation);​ + + // PUBLIC_CHANNEL has the integer value 0 + llSay(PUBLIC_CHANNEL,​ + "​llAngleBetween(ZERO_ROTATION,​ " + (string)currentRootRotation + ") = " + (string)angle);​ + } + } + ​ - ==== Example use cases: ​==== + ===== See Also ===== - + ==== Functions ​==== - + * [[wiki:​scripting_portal:​lsl_functions:​llRotBetween|llRotBetween]] - + * [[wiki:​scripting_portal:​lsl_functions:​llRot2Angle|llRot2Angle]] – Similar functionality used for the Axis-Angle format - ===== Examples ​===== + + ===== Deep Notes ===== + ==== Reference ==== + float AngleBetween(rotation a, rotation b)//simple but turns out to not be very accurate. + { + return 2.0 * llAcos( llFabs(a.x * b.x + a.y * b.y + a.z * b.z + a.s * b.s) + / llSqrt((a.x * a.x + a.y * a.y + a.z * a.z + a.s * a.s) + * (b.x * b.x + b.y * b.y + b.z * b.z + b.s * b.s))); + } + ​ + + float AngleBetween(rotation a, rotation b)//more complex implementation but more accurate, and reasonably fast. + { + rotation r = b / a; // calculate the rotation between the two arguments as quaternion + float s2 = r.s * r.s; // square of the s-element + float v2 = r.x * r.x + r.y * r.y + r.z * r.z; // sum of the squares of the v-elements + + if (s2 < v2) // compare the s-component to the v-component + return 2.0 * llAcos(llSqrt(s2 / (s2 + v2))); // use arccos if the v-component is dominant + if (v2) // make sure the v-component is non-zero + return 2.0 * llAsin(llSqrt(v2 / (s2 + v2))); // use arcsin if the s-component is dominant + + return 0.0; // one or both arguments are scaled too small to be meaningful, or the values are the same, so return zero + }//Written by Moon Metty @ Second Life & Miranda Umino @ Second Life. Minor optimizations by Strife Onizuka @ Second Life.