Vertex, as the compulsory keyword, is followed by its identification number. A vertex may be determined either by three coordinates preceded by keyword xyz or by fixation to either of vertex, curve, or surface. This is expressed by keyword fixed followed by the appropriate entity keyword ( vertex, curve, or surface) and its identification number. When the fixation to curve or surface is used parametric coordinates preceded by keyword t in the case of curve or uv in the case of surface must be provided otherwise the parametric position of the vertex on the curve or surface is calculated using its coordinates specified after keyword xyz or inherited from the parent vertex. If the position of the vertex on a parent entity is overdetermined the redundant information is used to avoid ambiguity of the vertex position. Note that the original position (given by real coordinates) of the vertex and its position on the parent entity (given by parametric coordinates) are not allow to differ by more than user defined epsilon specified on the command line. A vertex may be fixed simultaneously to a vertex and curve or to a vertex and surface. In this case, repeated use of keyword fixed is allowed. A size specification may be assigned to a vertex. This can be done using keyword size followed by a concrete number or a special keyword, optionally followed by a multiplication factor preceded by an asterisk. Special keyword def stands for a default mesh size specified on the command line when running the program, uni denotes the uniform mesh size specified on the command line, ver, cur, and sur is used in the case of fixation when the mesh size is to be the same as on the appropriate parent model entity (vertex, curve, or surface) at vertex location. By default, a vertex fixed to a parent entity inherits mesh size from that entity. In the case of a multiple fixation to vertex and curve or surface the mesh size of parent curve or surface is used. If no size is specified and the vertex is not fixed to any entity the default size from command line is used. Only positive mesh size is allowed at vertices. Note that the size assigned to a vertex is used for interpolation of mesh size over curves and surfaces sharing that vertex. The unit weight is assumed for all non-fixed vertices unless a weight is specified after keyword weight. Only positive weight specification is accepted. A vertex fixed to a parent entity inherits weight from that entity. Note that this inherited weight can be overridden by new weight specification (keyword weight) only in the case of vertex to vertex fixation. Keyword factor is used to specify the vertex mesh size multiplication factor. Note that this factor is not used when interpolating mesh size specification over curves and surfaces sharing the vertex. Setting it to zero will cause excluding this vertex from local mesh size control. Negative mesh size factors are not accepted. Default value of mesh size factor is equal to 1. An integer property number may be assigned to a vertex after keyword property. Keyword virtual marks a vertex as virtual. Keyword hidden marks it as a hidden one, which means that the location of the mesh node associated with this vertex is not fixed and may change during the smoothing process. The output of node generated at vertex position may be enforced or suppressed by setting yes or no after output keyword. By default, each physical non-hidden vertex is designated for output, except those fixed vertices with no physical ancestor designated for output. Suppressed output for a vertex bounding a physical curve or fixed to a physical curve designated for output is ignored. If generation of elements on a model entity between the vertex being just defined and other close vertices (already defined) bounding that entity is to be prevented, the other vertices should be specified after keywords coincide vertex. Neither from the coinciding vertices is allowed to be fixed to physical vertex or vertex with physical ancestor.
In the current implementation, the keyword hidden is ignored.