Primitives Reference: Difference between revisions
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=== Technic axle primitives === | ===Technic axle primitives=== | ||
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| [[File:Axle.png|200px|thumb|alt=Axle]] | | [[File:Axle.png|200px|thumb|alt=Axle]] | ||
|| This primitive | ||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. | ||
|- | |||
| '''axleend.dat''' || '''Technic axle end''' | |||
|- | |||
| [[File:axleend.png|200px|thumb|alt=Axleend]] | |||
||This primitive is used to produce the "plus-shaped" cross section of a technic axle. | |||
|- | |||
| '''axlehole.dat''' || '''Technic axle hole - closed''' | |||
|- | |||
| [[File:Axlehole.png|200px|thumb|alt=Axlehole]] | |||
||This primitive produces a technic axle hole with the disc ends and all sides. It may be scaled in the {y} dimension as necessary. | |||
|- | |||
| '''axlehol2.dat''' || '''Technic axle hole - side edges''' | |||
|- | |||
| [[File:Axlehol2.png|200px|thumb|alt=Axlehol2]] | |||
||This primitive produces the edges at the ends of the "plus-shaped" technic axle. | |||
|- | |||
| '''axlehol3.dat''' || '''Technic axle hole - tooth outer edges''' | |||
|- | |||
| [[File:Axlehol3.png|200px|thumb|alt=Axlehol3]] | |||
||This primitive produces the outer edges of the teeth of a technic axle hole. | |||
|- | |||
| '''axlehol4.dat''' || '''Technic axle hole - open one side''' | |||
|- | |||
| [[File:Axlehol4.png|200px|thumb|alt=Axlehol4]] | |||
||This primitive produces a technic axle hole with one side omitted. It may be scaled in the {y} dimension as necessary. | |||
|- | |||
| '''axlehol5.dat''' || '''Technic axle hole - open two opposite sides''' | |||
|- | |||
| [[File:Axlehol5.png|200px|thumb|alt=Axlehol5]] | |||
||This primitive produces a technic axle hole with two opposite sides omitted. It may be scaled in the {y} dimension as necessary. | |||
|- | |||
| '''axlehol6.dat''' || '''Technic axle hole tooth''' | |||
|- | |||
| [[File:Axlehol6.png|200px|thumb|alt=Axlehol6]] | |||
||This primitive represents one tooth of a technic axle hole. It may be scaled in the {y} dimension as necessary. | |||
|- | |||
| '''axlehol7.dat''' || '''Technic axle hole - sides''' | |||
|- | |||
| [[File:Axlehol7.png|200px|thumb|alt=Axlehol7]] | |||
||This primitive comprises a 1LDu long section of outer sides of a technic axle. It may be scaled in the {y} dimension. | |||
|- | |||
| '''axlehol8.dat''' || '''Technic axle hole perimeter''' | |||
|- | |||
| [[File:Axlehol8.png|200px|thumb|alt=Axlehol8]] | |||
||This primitive comprises a 1LDu long section of technic axle, without any ends. It may be scaled in the {y} dimension as necessary. | |||
|- | |||
| '''axlehol9.dat''' || '''Technic axle hole - tooth inner edges''' | |||
|- | |||
| [[File:Axlehol9.png|200px|thumb|alt=Axlehol9]] | |||
||This primitive produces the inner edges of the "plus-shaped" technic axle. | |||
|- | |||
| '''axleho10.dat''' || '''Technic axle hole - tooth surface''' | |||
|- | |||
| [[File:Axleho10.png|200px|thumb|alt=Axleho10]] | |||
||This primitive is used to produce the fill the "plus-shaped" cross section of a technic axle to the bounding circle. | |||
|- | |||
| '''Axlehol0.dat''' || '''Technic Axle Hole Hint''' | |||
|- | |||
| [[File:Axlehol0.png|200px|thumb|alt=Axlehol0]] | |||
||This file is an invisible "axlehole" that can be used to hint irregular axleholes that cannot be modeled with conventional axlehole primitives. To use: add an axle.dat in your part, apply position and scaling so that it fills the axlehole, and substitute it with this primitive.<br> | |||
Note that the bounding circle in the image is for context only - there are no actual geometry producing lines contained in these files. | |||
|} | |} | ||
{| class="wikitable" | |||
|+ | |||
===Reduced axle hole=== | |||
|- | |||
| '''axl2hole.dat''' || '''Technic axle hole reduced''' | |||
|- | |||
| [[File:Placeholder.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. | |||
|-} | |||
Revision as of 06:30, 5 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.
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





























































































