Geometry

It is recognized that there is a desire for modelling accuracy and detail, but it does come with a cost. The main purpose of the transfer is to provide a 3D backdrop against which further design work can continue. It is not intended that the model as exported from AVEVA E3D Design will be modified itself.

The level of detail and complexity of modelling in AVEVA E3D Design can have very significant effect on the resultant file size.

Some of the situations that have been encountered are:

• Modelling very small detail, such as fillet radii, small holes or small items such as rivets, washers and bolts can create many more entities in the IFC file than is practical. Additionally, some applications are not able to operate on very small objects.

• Using complex primitives can cause the exporter to resort to representing the geometry as facets whichever geometry flag has been used. Not all the AVEVA E3D Design basic primitives are replicated by their IFC equivalent: the most important ones are. As the System continues to be developed, more core primitives will be covered. Those that are not covered, will be faceted.

• Holes and Boolean operations are ways in which solid geometry is modified by having bits removed. A significant example is the end detailing of structural members. An unmodified linear structural member can be transferred as a simple extruded solid. Once there is end detailing, the translator must convert it into facets. There are Boolean operations in the IFC schema, but not all receiving systems are able to handle them.

• The arc tolerance determines the accuracy of rendering curved edges: the smaller the arc tolerance the more realistic curved edges look. A large arc tolerance makes circles display like a boundary with many straight sides. The more realistic the curves are with a smaller arc tolerance; the more facets are created and therefore the IFC file is larger.