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Function: llSetLinkAlpha( integer link, float alpha, integer face );

If a prim exists in the link set at link, set the Blinn-Phong alpha on face of that prim.

• integer link Link number (0: unlinked, 1: root prim, >1: child prims and seated avatars) or a LINK_* flag
• float alpha from 0.0 (clear) to 1.0 (solid) (0.0 <= alpha <= 1.0)
• integer face face number or ALL_SIDES

If face is ALL_SIDES then the function works on all sides.

Flag Description
LINK_ROOT 1 refers to the root prim in a multi-prim linked set[1]
LINK_SET -1 refers to all prims
LINK_ALL_OTHERS -2 refers to all other prims
Flag Description
LINK_ALL_CHILDREN -3 refers to all children, (everything but the root)
LINK_THIS -4 refers to the prim the script is in


  • The function silently fails if its face value indicates a face that does not exist.
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// Make the entire object disappear for 5 seconds

    touch_start(integer num_detected)
        // transparent
        llSetLinkAlpha(LINK_SET, 0.0, ALL_SIDES);

        // opaque
        llSetLinkAlpha(LINK_SET, 1.0, ALL_SIDES);
// when the object is touched,
// fade it out and back in again

    touch_start(integer num_detected)
        // fade out
        float alpha = 1.0;
        while (alpha >= 0.0)
            llSetLinkAlpha(LINK_SET, alpha, ALL_SIDES);
            alpha -= 0.001;

        // fade in
        while (alpha < 1.0)
            alpha += 0.001;
            llSetLinkAlpha(LINK_SET, alpha, ALL_SIDES);
// Makes selected prims in a linkset become transparent or visible on chat command. Give each prim a unique name.

list PrimList = ["ALL"];
// Start our prim list with a dummy entry, so that the index into this list will correspond directly to the link number
// By making the dummy entry 'ALL' we provide a match for that option too

    changed (integer change)
	if (change & CHANGED_LINK)

	integer PrimCount = llGetNumberOfPrims();
	llListen(37, "", NULL_KEY, "");  		    //  listen to chat commands from anyone on channel 37
	integer i;
	for (i = 1; i <= PrimCount; ++i)
	    PrimList += llToUpper(llGetLinkName(i) );  	    // Build a list of upper-case link names, where list position equals link number

    listen(integer channel, string name, key id, string msg)
	list    TempList = llCSV2List( llToUpper(msg) );    // make a list from upper-case version of user command line
	integer ListLen  = llGetListLength (TempList);
	integer alpha    = (llList2String(TempList, 0) == "SHOW");
	// 'SHOW' sets selected prims visible, otherwise set them transparent
	// e.g.  HIDE,PLATE,SPOON,NAPKIN	            <---- makes named prims invisible
	// e.g.  SHOW,ALL                                   <---- makes all prims visible

	integer i;
	for (i = 1; i < ListLen; ++i)
	    string  ThisPrim   = llStringTrim(llList2String(TempList, i), STRING_TRIM);
	    integer LinkNumber = llListFindList(PrimList, [ThisPrim]);
	    if (~LinkNumber)    // i.e. if LinkNumber != -1
		if (!LinkNumber)
		    LinkNumber = LINK_SET;   	// list position 0 is 'ALL'

		llSetLinkAlpha(LinkNumber, alpha, ALL_SIDES);


Link Numbers

Each prim that makes up an object has an address, a link number. To access a specific prim in the object, the prim's link number must be known. In addition to prims having link numbers, avatars seated upon the object do as well.

  • If an object consists of only one prim, and there are no avatars seated upon it, the (root) prim's link number is zero.
  • However, if the object is made up of multiple prims or there is an avatar seated upon the object, the root prim's link number is one.

When an avatar sits on an object, it is added to the end of the link set and will have the largest link number. In addition to this, while an avatar is seated upon an object, the object is unable to link or unlink prims without unseating all avatars first.

Counting Prims & Avatars

There are two functions of interest when trying to find the number of prims and avatars on an object.

integer GetPrimCount() { //always returns only the number of prims
    if(llGetAttached())//Is it attached?
        return llGetNumberOfPrims();//returns avatars and prims but attachments can't be sat on.
    return llGetObjectPrimCount(llGetKey());//returns only prims but won't work on attachments.
See llGetNumberOfPrims for more about counting prims and avatars.


If a script located in a child prim erroneously attempts to access link 0, it will get or set the property of the linkset's root prim. This bug (BUG-5049) is preserved for broken legacy scripts.

See Also


•  changed CHANGED_COLOR


•  llGetLinkNumber Returns the link number of the prim the script is in.
•  llGetAlpha Gets the prim's alpha
•  llSetAlpha Sets the prim's alpha
•  llGetColor Gets the prim's color
•  llSetColor Sets the prim's color
•  llSetLinkColor
•  llSetLinkTexture
•  llSetLinkPrimitiveParams


•  Translucent Color

Deep Notes

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  1. ^ LINK_ROOT does not work on single prim objects. Unless there is an avatar sitting on the object.


function void llSetLinkAlpha( integer link, float alpha, integer face );