Additive Manufacturing File Format
AMF icon
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| Filename extension | .amf |
|---|---|
| Internet media type | application/x-amf |
| Developed by | ASTM/ISO |
| Initial release | May 2, 2011 |
| Latest release |
1.2
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| Standard | ISO / ASTM52915 - 13 |
Additive Manufacturing File Format (AMF) is an open standard for describing objects for additive manufacturing processes such as 3D printing. The official ISO/ASTM 52915:2013standard is an XML-based format designed to allow any computer-aided design software to describe the shape and composition of any 3D object to be fabricated on any 3D printer. Unlike its predecessor STL format, AMF has native support for color, materials, lattices, and constellations.
An AMF can represent one object, or multiple objects arranged in a constellation. Each object is described as a set of non-overlapping volumes. Each volume is described by a triangular mesh that references a set of points (vertices). These vertices can be shared among volumes belonging to the same object. An AMF file can also specify the material and the color of each volume, as well as the color of each triangle in the mesh. The AMF file is compressed using the zip compression format, but the ".amf" file extension is retained. A minimal AMF reader implementation must be able to decompress an AMF file and import at least geometry information (ignoring curvature).
The AMF file begins with the XML declaration line specifying the XML version and encoding. The remainder of the file is enclosed between an opening <amf> element and a closing </amf> element. The unit system can also be specified (millimeter, inch, feet, meter or micrometer). In absence of a units specification, millimeters are assumed.
Within the AMF brackets, there are five top level elements. Only a single object element is required for a fully functional AMF file.
The format uses a Face-vertex polygon mesh layout. Each top-level <object> element specifies a unique id. The <object> element can also optionally specify a material. The entire mesh geometry is contained in a single mesh element. The mesh is defined using one <vertices> element and one or more <volume> elements. The required <vertices> element lists all vertices that are used in this object. Each vertex is implicitly assigned a number in the order in which it was declared, starting at zero. The required child element <coordinates> gives the position of the point in 3D space using the <x>, <y> and <z> elements. After the vertex information, at least one <volume> element must be included. Each volume encapsulates a closed volume of the object, Multiple volumes can be specified in a single object. Volumes may share vertices at interfaces but may not have any overlapping volume. Within each volume, the child element <triangle> is used to define triangles that tessellate the surface of the volume. Each <triangle> element will list three vertices from the set of indices of the previously defined vertices given in the <vertices> element. The indices of the three vertices of the triangles are specified using the <v1>, <v2> and <v3> elements. The order of the vertices must be according to the right-hand rule, such that vertices are listed in counter-clockwise order as viewed from the outside. Each triangle is implicitly assigned a number in the order in which it was declared, starting at zero.
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