Prims

Introduction

Primitives in Second Life are constructed by starting with a basic two dimensional shape, modifying it, and extruding it in to the third dimension along a path while applying modifications to the extrusion. The most basic example is a cube which starts out as a 2D square and extrudes along a linear path with no modifications to make a cube. A cylinder starts out as as circle and extrudes along the same linear path. If the circle was extruded along a circular path you would create a ring, and if a half-circle is extruded along another type of circular path you create a sphere.

2D Shape (Profile)

• ProfileCurve
  • Two combined enums: the lower 4 bits define the outer profile shape, and the high 4 bits define the type of hole if ProfileHollow is non-zero

Profile Shape:
Circle = 0x00
Square = 0x01
Isometric Triangle = 0x02
Equal Triangle = 0x03
Right Triangle = 0x04
Half Circle = 0x05

Hole Shape:
Same = 0x00
Circle = 0x10
Square = 0x20
Triangle = 0x30

2D Shape (Profile) Modifications

• ProfileBegin
  • Where the cut (if any) in the profile begins
• ProfileEnd
  • Where the cut (if any) in the profile ends
• ProfileHollow
  • How much of the profile is hollowed out, as a percent of the original bounding box. If non-zero this creates a hole using the shape defined in the higher bits of ProfileCurve

Extrusion (Path)

• PathCurve
  • Enum for the extrusion path. For whatever reason only the upper bits are used in this field:

Line = 0x10
Circle = 0x20
Circle2 = 0x30
Test = 0x40 // ???
Flexible = 0x80

Extrusion (Path) Modifications

• PathBegin
• PathEnd
• PathScaleX
• PathScaleY
• PathShearX
• PathShearY
• PathTwistBegin
• PathTwist
• PathRadiusOffset
• PathTaperX
• PathTaperY
• PathRevolutions
• PathSkew