Linking Prims - The Root Prim

Prim attachements/garments usually consist of multiple prims that are permanently attached (or ‘linked’) to each other. We do this by selecting them (Shift-Click each prim) and then pressing Ctrl+L (Apple+L on Mac).

An important concept to address is that of the ‘root’ or ‘parent’ prim in a set of linked prims. The root prim is the last prim to be selected when linking several prims.

When positioning a set of linked prims, the orientation and position is determined by the root prim.

When making prim clothes (or an attachment)  that consist of several linked prims, it is often useful to add a small root prim, which is selected last when linking. Thus, when adjusting clothing, it is really the root prim that is adjusted (the other linked prims merely follow passively).

Another important property of the root prim is that the name of the linked set (or clothing item) is determined by the root prim. Similarly, the name of the creator of the linked set is also determined by the root prim.

Let me illustrate by making a pair of linked reading glasses using 3 prims. I make a small cylinder (Y rotate 90 degrees) and produce 2 extra copies by shift-dragging the green arrow while in edit mode. The middle piece is altered by changing Y-rotate of the middle prim to 0, x-rotate to 90 and by adjusting the size.

Now I link them as follows: I click on left prim first to select it. Holding the shift key, I click on right prim. Still holding the shift key, I finally click on the middle piece (which will become the root prim). Link them all by pressing Ctrl+L.

slide3Notice that the prims on the left and right sides are highlighted in blue (while we are in edit mode). However, the root prim (middle piece) is highlighted by a yellow outline. It is this yellow piece that will be adjusted when wearing the linked attachment and that gives the attachment its name.

As before, I can wear these reading on my nose. These ‘glasses’ can now be easily adjusted to fit the face by moving and rotating the root prim of the linked set.

The principles illustrated up to now are: a) how to rez prims and b) how to link them. We also know the importance and properties of the ‘root’ or ‘parent’ prim in a linked prim set and how this can be utilized when fitting a linked set of prims to an Avatar.