Primitives Reference: Difference between revisions
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|[[File:Npeghol20.png|200px|thumb|alt=Npeghol20]] | |[[File:Npeghol20.png|200px|thumb|alt=Npeghol20]] | ||
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| [[File:Tooth16.png|200px|thumb|alt=Tooth16]] | | [[File:Tooth16.png|200px|thumb|alt=Tooth16]] | ||
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| '''tooth16.dat''' || '''Tooth for 16-tooth Technic gears''' | |||
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| [[File:Tooth16.png|200px|thumb|alt=Tooth16]] | |||
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| '''tooth24.dat''' || '''Tooth for 24-tooth Technic gears''' | |||
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| [[File:Tooth24.png|200px|thumb|alt=Tooth24]] | |||
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| '''tooth24a.dat''' || '''Tooth for 24-tooth Technic Crown Gear Type 2''' | |||
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| [[File:Tooth24a.png|200px|thumb|alt=Tooth24a]] | |||
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| '''tooth24b.dat''' || '''Tooth for 24-tooth Technic Crown Gear Type 3''' | |||
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| [[File:Tooth24b.png|200px|thumb|alt=Tooth24b]] | |||
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| '''tooth24c.dat''' || '''Tooth for 24-tooth Technic Crown Gear Type 1''' | |||
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| [[File:Tooth24c.png|200px|thumb|alt=Tooth24c]] | |||
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| '''tooth40.dat''' || '''Tooth for 40-tooth Technic gears''' | |||
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| [[File:Tooth40.png|200px|thumb|alt=Tooth40]] | |||
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| '''toothb12.dat''' || '''Tooth for 12-tooth Technic bevel gears''' | |||
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| [[File:Toothb12.png|200px|thumb|alt=Toothb12]] | |||
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| '''toothb14.dat''' || '''Tooth for 14-tooth Technic bevel gears''' | |||
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| [[File:Toothb14.png|200px|thumb|alt=Toothb14]] | |||
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| '''toothb20.dat''' || '''Tooth for 20-tooth Technic bevel gears''' | |||
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| [[File:Toothb20.png|200px|thumb|alt=Toothb20]] | |||
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| '''tootb28.dat''' || '''Full size tooth for 28-tooth Technic bevel gears''' | |||
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| [[File:Tootb28.png|200px|thumb|alt=Tootb28]] | |||
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| '''tootb28s.dat''' || '''Short tooth for 28-tooth Technic bevel gears''' | |||
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| [[File:Tootb28s.png|200px|thumb|alt=Tootb28s]] | |||
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| '''toothd28.dat''' || '''Tooth for 28-tooth Technic Differential''' | |||
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| [[File:Toothd28.png|200px|thumb|alt=Toothd28]] | |||
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| '''toothr.dat''' || '''Tooth for Technic Gear Racks''' | |||
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| [[File:Toothr.png|200px|thumb|alt=Toothr]] | |||
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| '''toothl.dat''' || '''Tooth for Large Technic Gears''' | |||
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| [[File:Toothl.png|200px|thumb|alt=Toothl]] | |||
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===Technic Duplo primitives=== | |||
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|colspan="2"| | |||
These primitives represent various components of the Duplo-scale technic parts. | |||
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| '''daxle.dat''' || '''Duplo technic axle section''' | |||
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|style="width: 200px;"|[[File:Placeholder.png|200px|thumb|alt=Daxle]] | |||
||This primitive is comprises a 1LDu long section of duplo technic axle, including its ends. It may be scaled in the {y} dimension to produce an axle of any length. | |||
|} | |} | ||
Revision as of 20:43, 23 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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