LlGetBoundingBox

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Summary

Function: list llGetBoundingBox( key object );

Returns a list that is the bounding box of object relative to its root prim, in local coordinates.
Format: [ (vector) min_corner, (vector) max_corner ]

• key object group, avatar or prim UUID that is in the same region

The bounding box is for the entire link set, not just the requested prim.
Returns an empty list ([]) if object is not found.

Specification

The physical representation of an object is made up of the shape of the prims and avatars seated upon it. The bounding box is the smallest possible cuboid which can contain the physical representation of the object and have its faces aligned to the object's local axes.

Caveats

  • Regardless if object is a non-root prim, the bounding box of the object is returned. This also applies if object is an agent sitting on an object - the bounding box of the sat-upon object (including the agent's shape) is returned.
  • Attachments have no bounding boxes of their own (as they have no physical interaction[1]), instead the bounding box of the avatar is returned.
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Examples

default//An avatar bounding box ruler thingy
{
    state_entry()
    {
        llSetStatus(STATUS_PHANTOM, TRUE);
    }
 
    touch_start(integer total_number)
    {
        key target = llDetectedKey(0);
        list box = llGetBoundingBox(target);
        vector center = llDetectedPos(0) + (llList2Vector(box, 0) + llList2Vector(box, 1)) * 0.5;
        vector size = llList2Vector(box, 1) - llList2Vector(box, 0);
        llSetPrimitiveParams([PRIM_POSITION, center, PRIM_SIZE, size]);
        llSetText("Name: " + llDetectedName(0) + ", UUID: " + (string)target + 
                "\nBounding Box Size: " + (string)size, <1.0, 1.0, 1.0>, 1.0);
    }
}
// Enclose a named object in the tightest possible box
// that is aligned with the object's root prim axes.
// Drop this script in a box near the object to enclose
// (must be in a 10m range)
 
string ObjectNameToEnclose = "SearchMe";
key UUID;
 
default
{
    state_entry()
    {
        llSensor(ObjectNameToEnclose, "", ACTIVE | PASSIVE, 10, PI);
    }
 
    sensor(integer n)
    {
        UUID = llDetectedKey(0);
        llSetTimerEvent(1);
    }
 
    timer()
    {
        list info = llGetObjectDetails(UUID, [OBJECT_POS, OBJECT_ROT]) + llGetBoundingBox(UUID);
        vector pos = llList2Vector(info, 0);
        rotation rot = llList2Rot(info, 1);
        vector corner1 = llList2Vector(info, 2) * rot + pos;
        vector corner2 = llList2Vector(info, 3) * rot + pos;
        vector size = llList2Vector(info, 3) - llList2Vector(info, 2);
 
        llSetPos((corner1 + corner2) * 0.5); // Set position to the midpoint (average) of the corners
        llSetRot(rot);
        llSetScale(size);
    }
}

Useful Snippets

//(bool) isInPrim - determines whether a given vector position in the region is within the borders of a cuboid,
// respecting the cuboid's rotation.
integer isInPrim(vector vPos)
{
    list bb = llGetBoundingBox(llGetKey());
    vector min = llList2Vector(bb, 0);
    vector max = llList2Vector(bb, 1);
    vPos = (vPos - llGetPos()) / llGetRot();
    float fTemp;
    if (min.x > max.x)
    {
        fTemp = max.x;
        max.x = min.x;
        min.x = fTemp;
    }
    if (min.y > max.y)
    {
        fTemp = max.y;
        max.y = min.y;
        min.y = fTemp;
    }
    if (min.z > max.z)
    {
        fTemp = max.z;
        max.z = min.z;
        min.z = fTemp;
    }
    if (vPos.x < min.x)
    {
        return FALSE;
    }
    if (vPos.y < min.y)
    {
        return FALSE;
    }
    if (vPos.z < min.z)
    {
        return FALSE;
    }
    if (vPos.x > max.x)
    {
        return FALSE;
    }
    if (vPos.y > max.y)
    {
        return FALSE;
    }
    if (vPos.z > max.z)
    {
        return FALSE;
    }
    return TRUE;
}

See Also

Functions

•  llGetAgentSize

Deep Notes

History

Sitting in 1.36

Avatars historically when they sit upon an object have been treated as part of the object, like a prim, even being assigned a link number (which can be used to detect and manipulate them to some extent). Unrelated to this, requesting the bounding box for a child prim of an object would return the bounding box for the entire object (unless it was an attachment, which point it would return the bounding box for the avatar). The first is something of a misfeature, the latter is an honest to goodness feature; the combination of these two lead to something interesting: Prior to 1.36 requesting the bounding box of an attachment while seated returned the bounding box for the object sat upon. It got reported as a bug SVC-1174, and the behavior was changed in 1.36. The bounding box for the object sat upon is unchanged by 1.36, the avatar still counts. However when the bounding box for the seated avatar is requested it does not fall through to the object being sat upon.

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Footnotes

  1. ^ Phantom and VolumeDetect do have physics interactions, which is why they still have bounding boxes.

Signature

function list llGetBoundingBox( key object );