Masterspec

5.0 Graphical/Geometric Object Modelling

This section of the standard defines the generic modelling requirements for the graphical element of the BIM object.

5.2  Geometric modelling requirements

   5.2  Geometric modelling requirements
This sub-section of the standard discusses the requirements for creating the geometric BIM object, including requirements for the insertion point, units, scale, tools to be used, dimensioning and labelling.
   
 5.2.1 Modelling tools
  The object shall be modelled using the corresponding or most appropriate tool/template from within the BIM authoring system.
Consideration shall be given to the tool/template selected in regards to the IFC designation that will be assigned to the object, see clause 3.1.
   
 5.2.2 Object origin point
  The object origin point (or base point) shall be established for the BIM object, from which all object geometry will be set out.
Object origin points shall be consistent for identical or similar object types to allow for simple substitution of alternative BIM objects.
The object origin point can correspond to the insertion point of the object, see clause 5.2.3.
   
 5.2.3  Insertion points
  An insertion point shall be established for the BIM object that logically represents the placement of the object in the project model.
Insertion points shall be consistent for identical or similar object types to allow for simple substitution of alternative BIM objects.
The insertion point should be located within the extent of the object.
Particular consideration shall be given to objects with parametric geometry to allow for the geometry of the object to change in the model environment and the object’s position to remain correct For example, the insertion point of a column should be on its centreline to allow the column size to be changed, if necessary, without changing the position of the centreline of the column.
NOTE: BIM authoring systems usually require structural items to have their insertion point in the centroid of that element to aid any analytical calculations that the model may be used for.
   
 5.2.4 Scale
  The object shall be modelled at a scale of 1:1.
   
 5.2.5 Units
  Metric geometry in millimetres shall be used unless specified otherwise by local requirements or if the scale of the object being modelled would better suit metres or kilometres.
   
 5.2.6 Fixed geometry
  Fixed geometry shall be used where it is not intended for the object to be modifiable. For example, a proprietary object that is only available in one size.
   
  5.2.7 Dimensioning
  All dimensions shall be constrained to reference items, such as planes, lines or points, rather than directly to geometry.
Dimensions shall be derived automatically using the associative dimensioning functions within the BIM authoring system.
Dimensions should be located beyond the extents of the object geometry.
Dimensions shall not overlap and shall be clear to read.
   
 5.2.8 Labels
  All labels shall be constrained to reference items, such as planes, lines or points, rather than directly to geometry.
Labels that reflect information contained within the object metadata shall match such data.
   
 5.2.9 Object colour
  The default colour of grey can be used for objects that represent physical elements available in more than one colour.
Alternatively, a representative colour for the physical element can be used.
   
 5.2.10 Drafting conventions
  Visual drafting conventions such as line types, hatching and fill shall be utilised, using the relevant tools available within the BIM authoring system, to distinguish between different parts of the object and to show variances in depth of surface in different views.
Hatching should be assigned to the relevant materials, or part description, for the object, rather than added as 2D information.
Symbolic lines should be used in plan views, rather than solid geometry.
The use of arrays, formulas and voids when modelling the object should be kept to a minimum.
2D lines and symbols can be used to indicate items that may not be modelled or to complement the 3D geometric information, such as to indicate flow direction or tap operating direction.
   
 5.2.11 Material assignment
  Proprietary objects should have appropriate materials assigned to them to represent the physical element’s constituent materials.
Generic objects can have materials assigned to them.

 

 

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