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Creating LDraw Parts:
LDraw 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.
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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. |
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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 rectangle in the {x,z} plane 80LDu x 40LDu.
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
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rect.dat
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Rectangle with all edges |
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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) should be given a scaling factor of 1.
1 16 0 0 0 5 0 0
0 1 0 0 0
20 rect.dat |
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box.dat
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Cuboid with all faces and edges |
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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. |
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box5.dat
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Cuboid with 5 faces and all edges |
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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. |
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box4.dat
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Cuboid with 4 faces and all edges |
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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. |
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box4t.dat
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Cuboid with 4 adjacent and all edges |
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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. |
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box4-1.dat
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Cuboid with 4 adjacent faces missing 1 edge |
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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. |
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box4-4a.dat
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Cuboid with 4 adjacent faces missing 4 edges |
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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. |
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box4-7a.dat
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Cuboid with 4 adjacent faces missing 7 edges |
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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. |
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box3#8p.dat
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Cuboid with 3 adjacent faces missing 8 edges (in two
parallel groups) |
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This primitive represents a cuboid missing the
top {-y} and left {-x} and right {+x} faces and excludes all
the edges of the left {-x} and right {+x} 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. |
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tri3.dat
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Right-angled triangular prism with 3 faces |
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This primitive represents a triangular prism
missing the top {-y} and bottom {+y} faces but including all
edges. The left {-x} and front {-z} faces are perpendicular.
Its origin is the right-angle corner of the (missing) top face
and by default has a size of 1LDu in each of the {x} and {z}
dimensions and 1LDu in the {y}
dimension. |
Curved primitives
LDraw represents curved surfaces as polygons. For circular
components two series of primitives are provided.
All the circular primitives are orientated in the {x,z} plane
with their origin at the centre of the circle and a default radius
of 1 LDu. Primitives are provided for complete circles and for
commonly used fractions of a complete circle. Where the naming
convention includes a prefix of the form n-f this indicates
the fraction (n/f) of the circle drawn by the primitive. Where this
fraction is less than an entire circle, the primitive starts at
{+x,0} and progresses in a conterclockwise direction when viewed
from above {-y}.
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1-8disc |
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1-4disc |
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2-4disc |
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3-4disc |
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4-4disc |
To avoid
matrix arithmetic problems in some renderers, the third dimension
({y} in the default orientation) of two-dimensional primitives
should be given a scaling factor of 1.
LDraw circles are normally
formed of 16-sided polygons (hexdecagons) - the regular
resolution. For larger elements, where scaling-up of
hexadecagons would give too angular an appearance, a series of
high resolution primitives based on a 48-sided polygon are
available. These may also be used for parts not well suited to a
16-fold symmetry.
These circular elements may be scaled by the same factor in both
the {x} and {z} dimensions to make circular elements of greater or
less than 1LDu radius. For example
1 16 0 0 0 3 0 0 0 1
0 0 0 3 4-4edge.dat
would generate a circle in the {x,z} plane with a diameter of
3LDu.
They may also be scaled asymmetrically in the x and z dimension
to make ellipses.
Although the default orientation is in the {x,z} plane the LDraw
language allows for these to be transformed
1 16 0 0 0 0 1 0 3 0
0 0 0 3 4-4edge.dat would
generate a circle in the {y,z} plane
1 16 0 0 0 3 0 0 0 0
3 0 1 0 4-4edge.dat would
generate a circle in the {x,y} plane
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n-fedge.dat
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Circular line segment |
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This suite of primitives are used for edges
which comprise an entire or part circle.
Currently
available primitives :
Regular resolution (n-f) : 1-8,
1-4, 3-8, 2-4, 3-4, 4-4
High resolution (n-f) : 1-8, 1-4,
2-4, 4-4 |
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n-fdisc.dat
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Circular disc sector |
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This suite of primitives are used for surfaces
which comprise an entire or part circle.
Currently
available primitives :
Regular resolution (n-f) : 1-8,
1-4, 2-4, 3-4, 4-4
High resolution (n-f) : 1-8,
1-4 |
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n-fndis.dat
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Inverse of circular disc sector |
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This suite of primitives pad their matching
n-fdisc.dat primitives out to the bounding square. They
are used to integrate circular elements into rectilinear
elements.
Currently available primitives
:
Regular resolution (n-f) : 1-8, 1-4, 2-4, 3-4,
4-4
High resolution (n-f) : 1-8, 1-4 |
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n-fringr.dat
n-frinrr.dat
ringr.dat
ringrr.dat
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Circular ring segment |
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This suite of primitives are used to generate
circular rings or part rings. The numeric suffix r in
the filename indicates the inner radius of the ring - the
outer radius is 1LDu greater. For example a n-fring4
primitive would create a ring with an inner radius of 4LDu and
an outer radius of 5LDu.
These primitives are currently
undergoing a change of naming convention - names of the form
"ringrr.dat" are being migrated to
"4-4rinrr.dat". Backward compatibility will be
maintained.
Currently available primitives
:
Regular resolution :
r=1 :
1-4ring1, 2-4ring1, ring1
r=2 : 1-4ring2,
2-4ring2, ring2
r=3 : 1-8ring3, 1-4ring3,
2-4ring3, ring3
r=4 : 1-4ring4, 2-4ring4,
ring4
r=5 : 1-4ring5,
4-4ring5
r=6 : 1-4ring6,
4-4ring6
r=7 : 1-4ring7, 2-4ring7,
ring7
r=8 :
1-4ring8
r=9 :
1-4ring9
r=10 : 1-4rin10,
ring10
r=12 :
1-4rin12
r=15 :
1-4rin15
r=16 :
1-4rin16
r=18 :
1-4rin18
r=19 :
1-4rin19
r=38 :
1-4rin38
r=39 : 1-4rin39
High
resolution :
r=3 :
1-4ring3
r=4 :
1-4ring4
r=9 : 1-4ring9,
4-4ring9
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n-fcyli.dat
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Circular cylinder |
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This suite of primitives are used to generate
cylinder or part cylinders.
Currently available
primitives :
Regular resolution (n-f) : 1-8, 1-4, 3-8,
2-4, 3-4, 4-4
High resolution (n-f) : 1-8, 1-4,
4-4
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n-fcyls.dat
n-fcyls2.dat
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Circular cylinder truncated by an angled
plane |
1-4cyls.dat
3-8cyls.dat
2-4cyls.dat
1-4cyls2.dat
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These primitives are used to generate
cylinders or part cylinders which are truncated by a plane
which is not perpendicular to the axis of the cylinder. The
default angle of the plane is 45 degress.
These
primitives are notoriously difficult to describe and the user
is encouraged to experiment in order to gain a full
understanding of their geometry. One technique is to open the
primitive in L3Lab, increase the zoom to 12800, deselect BFC
and choose random colours. Selecting Show Axes also
helps.
The 2-4cyls.dat primitive is orientated with the
perpendicular bounding plane at the top {-y} and the angled
bounding plane at the bottom {+y}. In common with the other
2-4xxxx.dat primitives, the {+z} semicircle is represented. By
default the truncation plane is y=x-1. The 1-4cyls.dat and
3-8cyls.dat primitives are sub-sections of
2-4cyls.dat
The 1-4cyls2.dat primitive is orientated
with the perpendicular bounding plane at the top {-y} and the
angled bounding plane at the bottom {+y}. Unlike the other
1-4xxxx.dat primitives, the {-x,+z} quadrant is represented.
The truncation plane is y=x.
The following observations
may help :
- 1-4cyls and 1-4cyls2 are complements. If you put them
together correctly they make a 1-4cyli.
1 15 0 0 0 1 0 0 0
1 0 0 0 1 1-4cyls.dat
1 14 0 1 0 -1 0
0 0 -1 0 0 0
1 1-4cyls2.dat
- 1-4cyls2 is actually hidden in 2-4cyls, which could be
constructed like
1 16 0 0 0 1 0 0 0
1 0 0 0 1 1-4cyls.dat
1 16 0 0 0 0 0
-1 0 1 0 1 0
0 1-4cyli.dat
1 14 0 1 0 1 0 0 0
1 0 0 0 1 1-4cyls2.dat
Currently available primitives
:
Regular resolution : 1-4cyls, 3-8cyls, 2-4cyls,
1-4cyls2
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n-fconr.dat
n-fconrr.dat
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Circular cone |
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This suite of primitives are used to generate
circular cones or part cones. The numeric suffix r in
the filename indicates the inner radius of the cone - the
outer radius is 1LDu greater. By default the cone is 1LDu high
in the {+y} dimension with the origin at the centre of the
outer diameter. For example a n-fcone4 primitive would
create a cone with an inner radius of 4LDu and an outer radius
of 5LDu.
Currently available primitives
:
Regular resolution :
r=1 :
1-4con1, 4-4con1
r=2 :
1-4con2
r=3 :
1-4con3
r=4 :
1-4con4
r=8 :
4-4con8
r=10 :
1-4con10
r=12 : 4-4con12
High
resolution :
r=5 :
1-4con5
r=6 :
1-4con6
r=9 : 1-4con9
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tffirrrr.dat
tfforrrr.dat
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Circular torus |
inner
outer |
This suite of primitives are used to generate
circular torus sections. By default all these primitives
produce a torus with a major radius of 1LDu, so typically need
to be scaled up in the {x} and {z} dimensions. The second and
third characters of the filename ff denotes the sweep
of torus, as an inverse fraction (01=1/1, 02=1/2, 04=1/4,
08=1/8, 16=1/16, 48=1/48). The last four chacters of the file
name rrrr denote the tube radius in LDu (1333=0.1333,
3333=0.3333).
Currently available primitives
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Regular resolution :
Inner :
t04i1333
Outer : t04o1333, t04o3333
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These diagrams (based on an idea of Paul Easter's)
illustrate the relationship of the torus primitives to
the major (orange) and minor (black) radii. |
inner |
outer |
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1-4ccyli.dat
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Circular torus section |
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This single primitive pre-dates the creation
of the tffirrrr and tfforrrr suite
of primitives and will not be augmented. It produces a quarter
torus with a major radius of 2.5Ldu and a tube radius of 1LDu.
It should be superceded by t04i4000.dat and
t04o4000.dat.
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n-fsphe.dat
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Sphere section |
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Currently available primitives
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Regular resolution : 1-8, 2-8, 4-8, 8-8
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1-8sphc.dat
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Spherical corner |
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This primitive represents one octant (eighth)
of a sphere, centered at the origin {0,0,0} of radius 1.414,
truncated by the sides of a cube with a vertex at {1,1,1}. The
boundaries of the resulting surface are circular and fit with
1-4edge.dat.
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Special purpose primitives
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Technic axle
primitives |
Top |
These primitives represent various components of the technic axle
and its matching hole. They are orientated in the {x,z} plane.
Except where noted below, and in the {y} dimension only, these
primitives should not be scaled.
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axle.dat
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Technic axle section |
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This primitive is comprises a 1LDu long section of technic
axle, including its ends. It may be scaled in the {y}
dimension to produce an axle of any length. |
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axlehole.dat
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Technic axle hole - closed |
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This primitive produces a technic axle hole with the disc
ends and all sides. It may be scaled in the {y} dimension as
necessary. |
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axleho11.dat
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Technic axle hole - reduced |
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This primitive produces a technic axle hole with reduced
teeth including the disc ends and all edges. It may be scaled
in the {y} dimension as necessary. |
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axlehol4.dat
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Technic axle hole - open one side |
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This primitive produces a technic axle hole with one side
omitted. It may be scaled in the {y} dimension as
necessary. |
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axlehol5.dat
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Technic axle hole - open two sides |
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This primitive produces a technic axle hole with two
opposite sides omitted. It may be scaled in the {y} dimension
as necessary. |
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axlehol6.dat
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Technic axle hole tooth |
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This primitive represents one tooth of a technic axle
hole. |
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axleend.dat
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Technic axle end |
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This primitive is used to produce the "plus-shaped" cross
section of a technic axle. |
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axleho10.dat
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Technic axle hole end |
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This primitive used to produce the fill the "plus-shaped"
cross section of a technic axle to the bounding circle. |
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axlehol7.dat
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Technic axle sides |
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This primitive is comprises a 1LDu long section of outer
sides of a technic axle. It may be scaled in the {y}
dimension. |
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axlehol8.dat
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Technic axle sides |
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This primitive is comprises a 1LDu long section of technic
axle, without any ends. It may be scaled in the {y} dimension
as necessary. |
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axlehol2.dat
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Technic axle outer edges |
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This primitive produces the edges at the ends of the
"plus-shaped" technic axle. |
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axlehol3.dat
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Technic axle hole edges |
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This primitive produces the outer edges of the teeth of a
technic axle hole. |
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axlehol9.dat
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Technic axle inner edges |
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This primitive produces the inner edges of the
"plus-shaped" technic axle. |
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These primitives are various representations of the castellated
technic bush. They are orientated with the technic axle hole along
the {y} axis and should not be scaled.
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bushlock.dat
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Technic 16-tooth castellation - long teeth |
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bushloc2.dat
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Technic 16-tooth castellation - regular teeth |
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bushloc3.dat
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Technic 16-tooth castellation - regular teeth
indented |
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This primitive differs from bushloc2.dat in that the teeth
are indented in four places to allow it to fit between four
adjacent studs. |
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bushloc4.dat
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Technic 16-tooth castellation - short teeth |
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steerend.dat
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Curved end to technic 1xn plate with 16-tooth
castellation on underside |
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These primitives are used to contruct technic connector pegs.
They are orientated with the technic axle hole along the {y} axis
and should not be scaled.
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connect.dat
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Technic connector - long with collar |
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connect2.dat
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Technic connector - long without collar |
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connect3.dat
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Technic connector - short with collar |
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connect4.dat
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Technic connector - short without collar |
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connect5.dat
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Technic connector - long with collar and slot |
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peghole.dat
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Technic connector hole |
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peghole2.dat
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Technic connector hole - 180 degrees |
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peghole3.dat
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Technic connector hole - 90 degrees |
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Each studxxx primitive described below has a
matching low resolution stu2xxx primitive, used by the
fast-draw mode of renderers - these stu2xxx primitive
should never be used in part files. An additional primitive
(studline.dat) is used to substitute a single line for studs by the
super fast-draw mode of LDraw.
All stud primitives are modelled with the solid disc uppermost,
even if designed for the underside of parts (stud3, stud4, stud8).
The origin is as the base of the stud and they extend for 4LDU in
the {-y} dimension. To use for the underside, the primitive need to
be inverted in the {y} dimension, viz.
1 16 x y z 1 0
0 0 -1 0 0 0
1 stud3.dat
These primitives should not be scaled in the {x} or {z}
dimensions. Ideally they should not be scaled in the {y} dimension
either, to allow the accurate substitution of chamfered studs by
high-quality renderers [but this rule is flouted in the regular
brick files, where stud4 is scaled by 5 to generate the underside
tube].
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stud.dat
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Regular stud |
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studp01.dat
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Regular stud with white dot |
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studel.dat
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Regular electric stud |
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The electric contact is on the {-x} {-z} corner |
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stud2.dat
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Hollow stud |
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stud2a.dat
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Hollow stud without edge around base |
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stud3.dat
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Small underside stud |
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This is modelled with the solid disc uppermost. To use for
the underside of plates, reference like
1
16 x y z 1 0 0 0 -1 0
0 0 1 stud3.dat |
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stud3a.dat
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Small underside stud without edge around base |
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See note for stud3. |
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stud4.dat
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Ring underside stud |
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See note for stud3. |
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stud4a.dat
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Ring underside stud without edge around base |
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See note for stud3. |
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stud5.dat
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Scala stud |
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stud6.dat
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Truncated hollow stud |
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For use on 2x2 round parts where the stud does not hang
over the edge of the part. |
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stud6a.dat
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Truncated hollow stud without edge around
base |
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For use on 2x2 round parts where the stud does not hang
over the edge of the part. |
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stud7.dat
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Duplo hollow top stud |
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stud8.dat
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Duplo hollow underside stud |
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This section comprises miscellaneous primitives that do not fit
neatly into any of the other categories. All are highly specialised
and represent components of parts which fit together with each other
or other standard parts. As such these primitives are not intended
to be re-sized.
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arm1.dat
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Cylindrical arm two-fingered hinge |
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This primitive produces two-fingered hinge
component of the cylindrical arm with a radius of 10LDu.
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arm2.dat
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Cylindrical arm three-fingered hinge |
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This primitive produces three-fingered hinge
component of the cylindrical arm with a radius of 10LDu.
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clip3.dat
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Horizontal clip |
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This primitive produces a horizontal clip
designed to hold an 8LDu diameter pole or rod.
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clip4.dat
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Vertical clip - three fingered |
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This primitive produces a three-fingered
vertical clip designed to hold an 8LDu diameter pole or rod.
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h1.dat
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Two-fingered plate hinge |
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This primitive produces the standard
two-fingered hinge with a depth of 8LDu - the thickness of a
plate. |
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h2.dat
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Three-fingered plate hinge |
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This primitive produces the standard
three-fingered hinge with a depth of 8LDu - the thickness of a
plate. |
Last updated 13 November 2002, to include LDraw updates up to
2002-04, by Chris
Dee.
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