WarpPos

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Revision as of 23:13, 31 December 2008 by Ppaatt Lynagh (talk | contribs) (Add quotes to distinguish the text copied from Forums.SecondLife.com from the body of this article; Also grow the quoted text to include the response from the anonymous Linden)
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WarpPos is a method by which the 10m limit on non-physical movement can be avoided, by exploiting an undocumented glitch in llSetPrimitiveParams in which multiple parameters are executed in a single server frame. <lsl>

warpPos( vector destpos ) 
{   //R&D by Keknehv Psaltery, 05/25/2006
    //with a little pokeing by Strife, and a bit more
    //some more munging by Talarus Luan
    //Final cleanup by Keknehv Psaltery
    //Changed jump value to 411 (4096 ceiling) by Jesse Barnett
    // Compute the number of jumps necessary
    integer jumps = (integer)(llVecDist(destpos, llGetPos()) / 10.0) + 1;
    // Try and avoid stack/heap collisions
    if (jumps > 411)
        jumps = 411;
    list rules = [ PRIM_POSITION, destpos ];  //The start for the rules list
    integer count = 1;
    while ( ( count = count << 1 ) < jumps)
        rules = (rules=[]) + rules + rules;   //should tighten memory use.
    llSetPrimitiveParams( rules + llList2List( rules, (count - jumps) << 1, count) );
    if ( llVecDist( llGetPos(), destpos ) > .001 ) //Failsafe
        while ( --jumps ) 
            llSetPos( destpos );
}

</lsl>

Note 1:

[Forums.SecondLife.com] blogs the news of this 2006-05 discovery, including:

""" A few observations: Sim crossings are perilous for AVs. Depending on connection speed and whether or not you are connected to the sim (can see it on the mini-map), it may screw up your client. However, it seems like objects, by themselves, can cross great distances. I managed to send an object 4 sims away diagonally. Further testing would help us to understand these things. ... The average time this function takes to execute is under .2 seconds, which is barely noticeable at all, and can easily be attributed to general lag. A simple optimization for an object with a known destination might be to calculate the list beforehand, and then call llSetPrimitiveParams with that list. ... a Linden ... response ... go ahead and find a workaround - I'd love to see it, I'm sure it is usefull, but it might not work very well across sim borders """

Note 2:

The comment ***The script limits the maximum distance to 1km, in order to prevent stack/heap collisions. Still, this is 100 times what llSetPos was limited to-- and you can, of course, modify it to allow larger distances, but beware.*** is outdated. Stack/heap is no longer a consideration with MONO. Maximum distance is now set for 4110 meters to account for an updated ceiling height of 4096 meters.