From 1eedc2b4af192973889341da5615139cfd65f152 Mon Sep 17 00:00:00 2001
From: dahlia
Date: Mon, 2 Feb 2015 02:47:47 -0800
Subject: Compute rotation for llLookAt() with local positive X axis pointing
 down

---
 .../Shared/Api/Implementation/LSL_Api.cs           | 25 ++++++++++------------
 1 file changed, 11 insertions(+), 14 deletions(-)

(limited to 'OpenSim/Region/ScriptEngine/Shared/Api/Implementation')

diff --git a/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs b/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
index 97e3eeb..debc262 100644
--- a/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
+++ b/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
@@ -3092,20 +3092,17 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
             // Determine where we are looking from
             LSL_Vector from = llGetPos();
 
-            // Work out the normalised vector from the source to the target
-            LSL_Vector delta = llVecNorm(target - from);
-            LSL_Vector angle = new LSL_Vector(0,0,0);
-
-            // Calculate the yaw
-            // subtracting PI_BY_TWO is required to compensate for the odd SL co-ordinate system
-            angle.x = llAtan2(delta.z, delta.y) - ScriptBaseClass.PI_BY_TWO;
-
-            // Calculate pitch
-            angle.y = llAtan2(delta.x, llSqrt((delta.y * delta.y) + (delta.z * delta.z)));
-
-            // we need to convert from a vector describing
-            // the angles of rotation in radians into rotation value
-            LSL_Rotation rot = llEuler2Rot(angle);
+            // normalized direction to target
+            LSL_Vector dir = llVecNorm(target - from);
+            // use vertical to help compute left azis
+            LSL_Vector up = new LSL_Vector(0.0, 0.0, 1.0);
+            // find normalized left axis parallel to horizon
+            LSL_Vector left = llVecNorm(LSL_Vector.Cross(up, dir));
+            // make up orthogonal to left and dir
+            up = LSL_Vector.Cross(dir, left);
+
+            // compute rotation based on orthogonal azes
+            LSL_Rotation rot = new LSL_Rotation(0.0, 0.707107, 0.0, 0.707107) * llAxes2Rot(dir, left, up);
 
             // Per discussion with Melanie, for non-physical objects llLookAt appears to simply
             // set the rotation of the object, copy that behavior
-- 
cgit v1.1