Primitives Reference: Difference between revisions
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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 | 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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===Two dimensional=== | ===Two dimensional=== | ||
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=== Three dimensional === | === Three dimensional === | ||
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| '''axle.dat''' || '''Technic axle section''' | | '''axle.dat''' || '''Technic axle section''' | ||
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| [[File:Axle.png|200px|thumb|alt=Axle]] | |style="width: 200px;"| [[File:Axle.png|200px|thumb|alt=Axle]] | ||
||This primitive 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. | ||This primitive 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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| '''axl2hole.dat''' || '''Technic axle hole reduced''' | | '''axl2hole.dat''' || '''Technic axle hole reduced''' | ||
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| [[File:Axl2hole.png|200px|thumb|alt=Axl2hole]] | |style="width: 200px;"| [[File:Axl2hole.png|200px|thumb|alt=Axl2hole]] | ||
||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. | ||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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| '''axl3hole.dat''' || '''Technic axle hole semi-reduced''' | | '''axl3hole.dat''' || '''Technic axle hole semi-reduced''' | ||
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| [[File:Axl3hole.png|200px|thumb|alt=Axl3hole]] | |style="width: 200px;"|[[File:Axl3hole.png|200px|thumb|alt=Axl3hole]] | ||
||This primitive produces a technic axle hole with semi-reduced teeth including the disc ends and all edges. It may be scaled in the {y} dimension as necessary. | ||This primitive produces a technic axle hole with semi-reduced teeth including the disc ends and all edges. It may be scaled in the {y} dimension as necessary. | ||
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| '''axlebeam.dat''' || '''Technic Axle Truncated to fit Technic Beam End Surface''' | | '''axlebeam.dat''' || '''Technic Axle Truncated to fit Technic Beam End Surface''' | ||
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| [[File:Axlebeam.png|200px|thumb|alt=Axlebeam]] | |style="width: 200px;"|[[File:Axlebeam.png|200px|thumb|alt=Axlebeam]] | ||
||This primitive produces the tip of an axle to be used between a cylinder of 9 LDu radius and an axle primitive. | ||This primitive produces the tip of an axle to be used between a cylinder of 9 LDu radius and an axle primitive. | ||
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| '''bushlock.dat''' || '''Technic 16-tooth castellation - long teeth''' | | '''bushlock.dat''' || '''Technic 16-tooth castellation - long teeth''' | ||
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| [[File:Bushlock.png|200px|thumb|alt=Bushlock]] | |style="width: 200px;"|[[File:Bushlock.png|200px|thumb|alt=Bushlock]] | ||
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| [[File:Steerend.png|200px|thumb|alt=Steerend]] | | [[File:Steerend.png|200px|thumb|alt=Steerend]] | ||
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===Technic bush primtives=== | |||
|- | |||
|colspan="2"| | |||
These primitives are usd to construct technic bush parts. | |||
|- | |||
| '''bush.dat''' || '''Technic bush with collar at one end''' | |||
|- | |||
|style="width: 200px;" |[[File:Bush.png|200px|thumb|alt=Bush]] | |||
|| | |||
|- | |||
| '''bush0.dat''' || '''Technic bush without end collars''' | |||
|- | |||
| [[File:Bush0.png|200px|thumb|alt=Bush0]] | |||
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|- | |||
| '''bush1.dat''' || '''Technic bush collar quarter''' | |||
|- | |||
| [[File:Bush1.png|200px|thumb|alt=Bush1]] | |||
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|- | |||
| '''bush2.dat''' || '''Technic Bush End 0.25''' | |||
|- | |||
| [[File:Bush2.png|200px|thumb|alt=Bush2]] | |||
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|} | |} | ||
Revision as of 13:57, 8 December 2023
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
Nomenclature
Boxes are named boxF, with F representing the number of faces a box has. The suffix E represents the number of edges removed.
F and E are may followed by an additional letter. The hyphen is removed if F is accompanied by a modifier.
Face modifiers:
- o - faces are opposite to each other
- t - faces are all touching each other (usually, it's implied, but box4t.dat is a thing)
- u - missing faces form a U-shape
Edge letters:
- p - groups of edges are parallel to each other
- a - some missing faces have no adjacent edges
Scaling and orientation
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.
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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}.
To avoid rounding errors, it is preferable to use existing fractional circular primitives, or create a new primitive, rather than rotate an existing primitive by anything other than 90 or 180 degrees. For example, use 3-16XXXX.dat rather than combining 1-8XXXX.dat with 1-16XXXX.dat rotated by 22.5 degreees.
To avoid matrix arithmetic problems in some renderers, the third dimension ({y} in the default orientation) of two-dimensional primitives must be given a non-zero scaling factor. 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 radius 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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Technic primitives
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