llMoveToTarget in front of an object

In the "How hard can this be?" category of questions, here I am demonstrating my complete lack of mathematical ability, I suspect.

I want an object to move along its local Z axis, in whatever direction it is pointed, but staying parallel to the ground (basically, making a fish people can sit on and steer, but control things can wait for later).

For testing purposes, I used a prim tapered on the Z axis, X axis pointed at the ground. On a touch, I wanted it to get its current position, then create a new position ten metres away on the z axis and start a MoveToTarget that way.

integer target;
float altitude=1;

default
{
    state_entry()
    {
        llSetStatus(STATUS_PHYSICS, TRUE);
    }

    touch_start(integer total_number)
    {
        
//Find out current rotation and sine/cosine of the angle of the global z axis thingee.  
        rotation rot=llGetRot();
        vector ang=llRot2Euler(rot);
        float cos= llCos(ang.z);
        float sine=llSin(ang.z);
        float abs= (ang.z/PI);
        llOwnerSay("Angle is "+(string)abs+"PI");
        llOwnerSay("Cosine is "+(string)cos);
        llOwnerSay("Sine is "+(string)sine);
  
//Now, use that to get a new position in global coordinates.  If my limited trig is right :P, sine is opposite over the hypotenuse, so that's the y axis displacement, x is the cosine.
 
   vector pos =llGetPos();
      llOwnerSay("position is "+(string)pos);
       vector newpos = pos+<10*cos,10*sine,altitude>;

//Now move there
       target=llTarget(newpos,1);
       llMoveToTarget(newpos,3);
       llLookAt(newpos,.1,.1);///keeps the object from wiggling as it moves
       pos =llGetPos();   
    }

    at_target(integer tnum, vector targetpos, vector ourpos)
    {
        //llOwnerSay("position is "+(string)ourpos);  //Wow, that's a chatty event, turned that off....
        llStopMoveToTarget();
        llStopLookAt();
    }
}

Really, I thought this would work, but it doesn't at all. I can get it to move back and forth nicely along one axis or another, but if I turn it to any non-cardinal heading, it seems rather random. Sometimes it just flips around.

I'm clearly doing something fundamentally wrong here. I mean, it is not even close to working. What am I missing?

I would try this:
vector nose = llRot2Up( llGetRot()); // unit vector pointing the direction of the prims Z axis
...and...
vector newpos = pos+10.0*nose;
.. inserted on proper places in your program and replacing the values you have


(is that an answer to the question?)

Well, THAT works. I didn't know about llRot2Up

Still doesn't fix my difficulty with trigonometry, but high school is over a decade in my rear window now, thank goodness.

I would seriously advise against Euler angles for anything other than entering a simple rotation about one of the three primary axes, and even then llAxisAngle2Rot() is probably more intuitive and less prone to defects during code maintenance.

http://www.lslwiki.net/lslwiki/wakka.php?wakka=llAxisAngle2Rot