set position of childprim using root position

[testgenord1]

Hi!
I would like to automatically set the position of a childprim on the same position as the root prim,  but 1 meter above the root prim.
This really should not be a problem, but for whatever reason, I cannot accomplish this.
The childprim always ends up several meters set away from the root prim in the x-position.
(The same also happens when I replace PRIM_POSITION with PRIM_POS.)

I can't figure out what is wrong.
Maybe you can find the mistake?

Thank you very much in advance!
Here is my script:

vector startpos;

default
{
    state_entry()
    {
        startpos = llGetPos();//Position of the rootprim
        llOwnerSay("startpos = " + (string)startpos);
        llSetLinkPrimitiveParamsFast(LINK_ALL_CHILDREN,[PRIM_POSITION,startpos - <0.0,0.0,1.0>]);//Position of the childprim
    }
}

[Rolig Loon]

Use PRIM_POS_LOCAL if you are setting a position relative to the root of the linkset.

[testgenord1]

Thank you for your quick reply.

I just don't understand why, but it doesn't seem to make any difference (that's what I meant with "PRIM_POS" in my original post, I really meant to write "PRIM_POS_LOCAL".
It leads to the same result.

The script seems to be logical that way.
I really can't see where the mistake is.

Any other ideas will be appreciated.

[Quistess Alpha]

A few things. llGetPos() isn't neccessarily the position of the root prim. for that you need http://wiki.secondlife.com/wiki/LlGetRootPosition.

so to fix your script you could say

default
{
    state_entry()
    {
        vector startpos = llGetRootPosition();//Position of the rootprim
        llOwnerSay("startpos = " + (string)startpos);
        llSetLinkPrimitiveParamsFast(LINK_ALL_CHILDREN,[PRIM_POSITION,startpos + <0.0,0.0,1.0>]);//Position of the childprim
    }
}

But as Rolig suggested it would be less error-prone to just

default
{
    state_entry()
    {
        llSetLinkPrimitiveParamsFast(LINK_ALL_CHILDREN,[PRIM_POS_LOCAL,<0.0,0.0,1.0>]);//Position of the childprim
    }
}

 

[Qie Niangao]

2 hours ago, testgenord1 said:

1 meter above the root prim

The meaning of "above" might be a problem. If the root is rotated relative to region coordinates, motion of the child prim(s) will be relative to the root, not the region. You may actually want that <0,0,1> offset to be rotated through the root rotation (<0,0,1> / llGetRootRotation() or something like that).

 

Edited June 19, 2021 by Qie Niangao
"/" not "*" because we're COMPENSATING for that root rotation, to put it back into region coordinates

[testgenord1]

Thank you very much for your idea.
I've further simplified the script to avoid errors.
The position of the childprim is now supposed ot be the same as the root prim's.

Unfortunately it didn't help.
(Renaming LINK_ALL_CHILDREN to link number "2" also didn't make any difference.)

I tried some debugging and had a really bizarre result using the script below.
The newly created vector of the linked prim ("newpos") produced the following result:

[12:21] Primitive: startpos = <380.697083,  77.889473,  21.167229>
[12:21] Primitive: newpos = <391.888062,  80.507759,  21.724491>
 

I really don't get it.
 

default
{
    state_entry()
    {
        vector startpos = llGetRootPosition();//Position of the rootprim
        llOwnerSay("startpos = " + (string)startpos);
        llSetLinkPrimitiveParamsFast(2,[PRIM_POSITION,startpos]);//Position of the childprim
        vector newpos = llList2Vector(llGetLinkPrimitiveParams(2,[PRIM_POSITION]),0);
        llOwnerSay("newpos = " + (string)newpos);
    }
}

 

[Qie Niangao]

Child prim positions are specified relative to the root, so if you try to set a child prim's position to "startpos" it will actually try to offset that child prim from the root by the region coordinates of the root prim. 

To put the child prim at the same location as the root, you'd set its position to <0,0,0> — that is, offset by nothing at all from that root position.

[Wulfie Reanimator]

PRIM_POSITION has a gotcha about how it works based on context.

When you're moving child links, PRIM_POSITION works the same as PRIM_POS_LOCAL.

So [PRIM_POSITION, llGetPos + <0,0,1>] is trying to move the prim very far away from the root, because it's the same as [PRIM_POS_LOCAL, llGetPos + <0,0,1>].

[testgenord1]

8 minutes ago, Qie Niangao said:

Child prim positions are specified relative to the root, so if you try to set a child prim's position to "startpos" it will actually try to offset that child prim from the root by the region coordinates of the root prim. 

To put the child prim at the same location as the root, you'd set its position to <0,0,0> — that is, offset by nothing at all from that root position.

Thank you very much, Qie Niangao.
So, using the same position as the root prim's for the child prim automatically creates an offset for the child prim's position?

Your advice seems to have done the trick.
I'm posting the script below.
Should I run into more problems, I'll come back again.

Thank you all for your help very much again! 🙂

default
{
    state_entry()
    {
        vector startpos = llGetRootPosition();//Position of the rootprim
        llOwnerSay("startpos = " + (string)startpos);
        llSetLinkPrimitiveParamsFast(LINK_ALL_CHILDREN,[PRIM_POSITION,<0,0,1>]);//Position of the childprim +1 meter offset in z-direction
        vector newpos = llList2Vector(llGetLinkPrimitiveParams(2,[PRIM_POSITION]),0);
        llOwnerSay("newpos = " + (string)newpos);
    }
}