Content in Second Life is created using the inworld building tools (see figure 7) which allow residents to construct objects by using a set of basic shapes, known as prims (primitives). The prims available are; cube, prism, pyramid, tetrahedron, cylinder, hemicyclinder, cone, hemicone, sphere, hemisphere, torus, tube, ring, tree and grass. As well as allowing their position, size and rotation to be adjusted, these basic shapes can be modified by resizing, twisting, hollowing, shearing, slicing, tapering, revolving, dimpling, stretching, cutting, or adjusting the size of holes in prims such as rings. These transformations are colloquially referred to as torturing.
Prims can be linked together to form complex objects. Prims within a linked set can be no more than thirty two metres apart, and there can be no more than 256 prims in a linked set. There is no capability to create hierarchical linked sets, i.e. to link linked sets to each other. This is a serious limitation, especially in the construction of working machines. Only prims owned by the same avatar can be linked, which is another annoying impediment to collaborative building1.
For most of my time in Second Life the maximum prim size able to be created was 10m in any dimension, though even larger and smaller objects were possible with a bit of creativity. Nano prims, i.e. under 1cm3 can be created by applying path cuts and otherwise torturing prims. Mega prims, i.e. over 10m3, while not then able to be created, were previously, and were also able to be created by exploiting bugs in the Second Life viewer which have occurred from time to time in the period since mega prims were disallowed. Copies of existing mega prims could be obtained from other residents or purchased. The basic shape of a mega prim can be changed, and it can be tortured, but any attempt to resize it will cause it to revert back to no more than 10m on a side. This is an arbitrary limit imposed by Linden Lab and does not apply to the OpenSimulator project2 where prims of any size may be created. Since 2011 Linden Lab increased the maximum size of prims to 64m3. I found it curious that Linden Lab did not allow mega prims sooner as they reduce server load by lowering the number of prims required to construct large objects. One possible reason is that if a mega prim is larger than the draw distance preference (i.e. the radius in metres of a circle surrounding your avatar within which the world is rendered), it will not be rendered by the viewer, resulting in avatars colliding with objects that are invisible to them. However, my experience suggests that the typical user has a draw distance of 200 metres, so incidences of this problem should be rare, except for extremely large mega prims.
Prims may have a number of attributes applied to them. Some prims can be made flexible, which allows them to be used in, for example, clothing creation. Prims can also be made phantom, which means they will then present no barrier, i.e. one can walk through a phantom prim. Prims can be made to emit light or to glow. All objects can also be made physical, which means that they will interact with the world’s physics engine. If one created an ordinary sphere one metre above the ground (creating objects in the world is known as rezzing, from resolved), it would simply hang in midair in the spot in which it was rezzed. Once the physical property is applied, the sphere will fall to the ground under the influence of the world’s gravity. One could then kick it around like a ball in meatspace.
This property produced the first occasion when I experienced a crossover of the two worlds of meatspace and virtual space. When I first discovered the physical property I spent many hours playing around with physical objects in the world. I made many shapes and kicked them around with my avatar. A few days later I had occasion to move a number of large cardboard boxes from inside my meatspace house to storage underneath the house. Rather than carry each one individually I kicked them down my sloped driveway towards the storage space under the house. As I did so I experienced a weird sensation of being in the wrong world. For a few moments I was back in the world kicking physical objects around.
Linked sets of objects with the physical property set can have a maximum of thirty two prims4. This means that as vehicles are physical objects they are limited to thirty two prims. Because highly detailed vehicles are prized a recent workaround to overcome this limitation has been the production of vehicles that are not actually vehicles as specified with LSL (Linden Scripting Language, see below) but which are worn by the avatar, as an avatar can wear more than thirty two prims.
The large volume of space available to the builder makes it possible to lose prims, and there is no inbuilt tool for finding them. There is not even provision to list all the objects on a given piece of land, unless one is the owner of that land. It is possible to build a scripted object that will scan for one’s objects, but the maximum number of objects it is possible to find this way is sixteen and a scanners’ maximum operating distance is limited to ninety six metres5.
Another type of object is the sculpted prim (known as sculpties)6. These are ordinary prims which have had a sculpt map applied to them. The sculpt map is an RGB image (presently of a maximum of 128×128 pixels in Second Life), where the colour values are interpreted as X, Y and Z coordinates respectively. Sculpt maps are created outside of Second Life, either using resident made tools7 or 3D rendering software8. Sculpted prims allow the creation of complex 3D shapes that require only one prim when rezzed in the world. There are some disadvantages to using sculpted prims, for example, they cannot be made flexible, and it is often necessary to set sculpted prims to phantom. This is because the physical intersection of an object is its bounding box, and, as sculpted prims can be a substantially different shape to the prim to which they are applied, collision difficulties occur.
- Wadley, G., Ducheneaut, N., (2009), “The ‘out-of-avatar experience’: object-focused collaboration in Second Life”, ECSCW’09: Proceedings of the 11th European Conference on Computer Supported Cooperative Work, 7-11 September 2009. Vienna, Austria, p. 335, http://people.eng.unimelb.edu.au/gwadley/pubs/ECSCW09-WadleyDucheneaut.pdf, Accessed 08/02/2014. ↩︎
- OpenSimulator, Main Page, http://opensimulator.org/wiki/Main_Page, Accessed 01/02/2011. ↩︎
- Second Life Wiki, Mega Prim, http://wiki.secondlife.com/wiki/Mega_Prim, Accessed 08/02/2014. ↩︎
- Second Life Wiki, Physical, http://wiki.secondlife.com/wiki/Physical, Accessed 08/02/2014. ↩︎
- LSL Wiki, llSensor, http://lslwiki.net/lslwiki/wakka.php?wakka=llSensor, Accessed 08/02/2014. ↩︎
- Second Life Wiki: Sculpted Prims: Technical Explanation, http://wiki.secondlife.com/wiki/Sculpted_Prim_Explanation, Accessed 08/02/2014. ↩︎
- Second Life Wiki, Sculpted Prims: Resident-made Tools, http://wiki.secondlife.com/wiki/Sculpted_Prims:_Resident-made_Tools, Accessed 08/02/2014. ↩︎
- Second Life Wiki, Sculpted Prims: 3d Software Guide, http://wiki.secondlife.com/wiki/Sculpted_Prims:_3d_Software_Guide, Accessed 08/02/2014. ↩︎