i working on webgl viewer of ifc file now. ifcrepresentation objects easy understand, however, not @ coordination transformation. there better expression translate , rotate object3d in threejs defined ifcaxis2placement3d? guess should rotate object z axis align z axis new vector, how implement ? questions ifcobjectplacement. requires sub placementrelto object until placementrelto == null. bit confused again, forward transformation or backward transformation if want read absolute coordinates placement? mean, use push-pop or direct order? example, if there matrix m1, m2.. mn, m = m1 x m2 x ... mn or m = mn x mn-1 x ... x m2 x m1? can find beautiful mesh objects in project position wrong. please me.
thanks.
take @ this article on matrix transformations projection primer on matrix transformations.
it's worth noting geometry in ifc model 'implicit' rather 'explicit' shapes. means processing needs performed before can data form feed typical 3d scene - , you'll missing lot of shapes model few explicitly modelled mesh. long , short geometry in ifc non-trivial (diagrams). that's before start on placement/mapping/ transformation world coordinate system.
it's not clear if using ifc toolkit process raw ifc step data. if not, i'd recommend save lot of work (likely years of work).
buildingsmart maintain list of resources process ifc (commercial , open source)
i know following toolkits reasonably mature , capable of processing geometry. have webgl implementations might able re-use.
- http://ifcopenshell.org/ifcconvert.html & https://github.com/opensourcebim
- https://github.com/xbimteam/xbimgeometry (disclosure - involved project)
- http://www.ifcbrowser.com/
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