Primitives Reference

LDraw Primitives Reference

This page is a source of reference for the LDraw primitives in the \LDraw\p directory. Primitives are defined as highly re-usable components of LEGO parts modelled for LDraw. They serve several purposes :

   * To speed up parts authoring by providing a library of components which can be incorporated into several parts
   * To allow rendering software to make substitutions of curved components

Within this reference material the available primitives are categorised into:

Each section contains an overview of the characteristics common to all primitives within that category. Primitives are grouped into classes within each category - one class of primitive serving a similar purpose at different sizes or resolutions. For each class of primitive, a brief description of the purpose of the primitive is provided, with notes on its co-ordinate origin, default size and rules for scaling. A list of the available primitives is shown.

An understanding of the orientation of the co-ordinate axes is essential for authoring a part for LDraw. For reference within this page the axes and their direction is shown in this diagram.

Rectilinear primitives

These rectilinear elements may be scaled in the {x}, {y} and {z} dimensions to make elements of any size. For example

1 16    0 0 0    40 0 0    0 1 0    0 0 20    rect.dat

would generate a 80LDu x 40LDu rectangle in the {x,z} plane.

Although the default orientation of the rect.dat primitive is in the {x,z} plane the LDraw language allows for this to be transformed

1 16    0 0 0    0 1 0    40 0 0    0 0 20    rect.dat

would generate a 80LDu x 40LDu rectangle in the {y,z} plane.

1 16    0 0 0    40 0 0    0 0 20    0 1 0    rect.dat

would generate a 80LDu x 40LDu rectangle in the {x,y} plane.

Two dimensional

rect.dat	Rectangle with all edges
	This primitive represents a rectangle in the {x,z} plane and the four edges that bound it. Its origin is at its centre and by default has a size of 2LDu in each of the {x} and {z} dimensions. To avoid matrix arithmetic problems in some renderers, the third dimension ({y} in the default orientation) must be given a non-zero scaling factor. 1 16    0 0 0    5 0 0    0 1 0    0 0 20    rect.dat
rect3.dat	Rectangle with 3 edges
	This primitive represents a rectangle in the {x,z} plane but excludes one edge {-z}. Its origin is at its centre and by default has a size of 2LDu in each of the {x} and {z} dimensions.
rect2p.dat	Rectangle with 2 parallel edges
	This primitive represents a rectangle in the {x,z} plane but excludes two parallel edges ({+x} and {-x}). Its origin is at its centre and by default has a size of 2LDu in each of the {x} and {z} dimensions.
rect2a.dat	Rectangle with 2 adjacent edges
	This primitive represents a rectangle in the {x,z} plane but excludes two adjacent edges ({-x} and {-z}). Its origin is at its centre and by default has a size of 2LDu in each of the {x} and {z} dimensions.
rect1.dat	Rectangle with 1 edge
	This primitive represents a rectangle in the {x,z} plane but include only the one {+x} edge. Its origin is at its centre and by default has a size of 2LDu in each of the {x} and {z} dimensions.
recte3.dat	Empty rectangle with three edges
	This primitive represents three edges of a rectangle in the {x,z} plane. Its origin is at its centre and by default has a size of 2LDu in each of the {x} and {z} dimensions.
recte4.dat	Empty rectangle with all edges
	This primitive represents the four edges of a rectangle in the {x,z} plane. Its origin is at its centre and by default has a size of 2LDu in each of the {x} and {z} dimensions.

Three dimensional

box.dat	Cuboid with all faces and edges
	This primitive is used to define a cuboid. Its origin is the centre of the cuboid and by default has a size of 2LDu in each of the three dimensions.
box5.dat	Cuboid with 5 faces and all edges
	This primitive represents a cuboid missing the top {-y} face. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box5-1.dat	Cuboid with 5 faces without 1 edge
	This primitive represents a cuboid missing the top {-y} face and one edge {-z} of that. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box5-2p.dat	Cuboid with 5 faces without 2 parallel edges
	This primitive represents a cuboid missing the top {-y} face and two of the four edges surrounding that. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box5-4a.dat	Cuboid with 5 faces without top edges
	This primitive represents a cuboid missing the top {-y} face and the four edges surrounding that. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box5-12.dat	Cuboid with 5 faces missing all edges
	This primitive represents a cuboid missing the top {-y} face and all edges. Its primary use is for sticker parts. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box4.dat	Cuboid with 4 parallel faces and all edges
	This primitive represents a cuboid missing the top {-y} and bottom {+y} faces. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box4o4a.dat	Cuboid with 4 parallel faces without bottom edges
	This primitive represents a cuboid missing the top {-y} and bottom {+y} faces, and missing the edges of the bottom face. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box4o8a.dat	Cuboid with 4 parallel faces without top and bottom edges
	This primitive represents a cuboid missing the top {-y} and bottom {+y} faces, and missing the edges of the top and bottom face. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box4t.dat	Cuboid with 4 adjacent and all edges
	This primitive represents a cuboid missing the top {-y} and front {-z} faces, but with all its edges. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box4-1.dat	Cuboid with 4 adjacent faces missing 1 edge
	This primitive represents a cuboid missing the top {-y} and front {-z} faces and the edge between those faces. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box4-2p.dat	Cuboid with 4 faces without two opposite top edges
	This primitive represents a cuboid missing the top {-y} and bottom {+y} faces, and missing two edges of the top face - the intersection of the two missing faces and the opposite edge. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box4-3p.dat	Cuboid with 4 faces without three parallel edges
	This primitive represents a cuboid missing the top {-y} and bottom {+y} faces, and missing three edges of the missing faces. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box4-4a.dat	Cuboid with 4 adjacent faces missing 4 edges
	This primitive represents a cuboid missing the top {-y} and front {-z} faces and all the edges of the missing front face. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.
box4-7a.dat	Cuboid with 4 adjacent faces missing 7 edges
	This primitive represents a cuboid missing the top {-y} and front {-z} faces and all the edges of both missing faces. Its origin is the centre of the (missing) top face and by default has a size of 2LDu in each of the {x} and {z} dimensions and 1LDu in the {y} dimension.