What does Prim mean?

[gloria200116]

I have been seeing the word a lot since I joined a few days ago  but cant figure out what it means.

[LittleMe Jewell]

Double post

 

[cykarushb]

Heres the wiki article on what a Prim or Primitive is.

http://wiki.secondlife.com/wiki/Primitive

Basically is a base 3D object that can be manipulated to create other objects.

[Lindal Kidd]

It's shorthand for "geometric primitive".  A geometric primitive is a basic geometric shape...a rectangular solid, a pyramid, a cylinder, a sphere.  (However, prims can be edited in various ways to produce quite a large variety of shapes!)  Before we had the ability to create mesh objects using external 3D modeling software, everything in SL was made out of prims, using the in-world building tools.

[Nalates Urriah]

Prims are a changing... and the wiki and other sources are not completely up to date. So, for a new person it will be confusing. 

I'll try to frame an explanation with a fluid time context so it hopefully makes sense in an evolutionary context. 

When SL started The Internet and computer speeds and power were vastly less than they are today. So, many shortcuts were taken to improve performance. One of those was the use of primitive geometric shapes. Open your build panel (Ctrl-B) and you'll see the basic shapes; cube, sphere, etc. Everything in SL was built with these shapes. Rather than download them from a central server system these shapes were built into the viewer. 

We needed different size spheres and cubes so parameters were used to modify the basic primitive shapes.We can twist a cube into odd shapes. The only thing we have to download from the servers is a small set of numbers, parameters. The vertex list of points that make up the mesh layout of a twisted cube, or whatever, is provided by the viewer. So, we call SL a parametric system. Visit  The Ivory Tower Library of Primitives (URL) to see what can be done with the basic primitives.

However, the system limited what we could build. If you look at clothes pre-2010, you'll see things look a bit primitive (the pun is intended). Also, images of Sl before 2010 have the place looking kind cubish.

Moving forward, to get more organic shapes a 'sculpty' primitive was created. Those are a primitive that gets it's list of vertices from an image file. The RGB values are used as X,Y,Z values and each pixel represents a vertex. We don't use these much anymore. They are a pain to figure out and make. Plus, these days they are slow to render because so few are used they are often not cached in the CDN system we are using.

In 2010 another type of primitive was added: mesh, which is why I use that date when talking about primitives and how SL looks. Everything in SL is mesh, vertices. Press Ctrl-Shift-R to switch to wireframe view and see the mesh. Press again to return to the rendered view. With mesh primitives we upload a list of vertices. With improved computer and Internet speeds downloading the list is not too much for the systems running SL. Then it gets confusing because we just call mesh primitives: mesh or rigged or fitted mesh and drop the word primitive.

In 2013 mesh primitives were changed so that they could be rigged to a new version of the avatar. Now mesh will follow an avatar shape.

So, almost everything in SL is a primitive or prim. Exceptions are the avatar, sky, clouds, ground... and quite often those get replaced by a prim...