1.1 Model Schema
The Dragonfly Model schema is an abstracted means of describing building geometry, which is intended to make it easier to build models of large buildings all of the way up to the scale of urban districts. While Dragonfly models are always translatable into full 3D format, the Dragonfly schema is fundamentally a 2D representation of Building geometry, where all rooms are assumed to be extrusions of floor plates. Such 2D rooms (aka. Room2Ds) represent the finest level of detail supported by the Dragonfly schema and all objects smaller than individual rooms like windows and shades are represented through simple sets of instructions (aka. WindowParameters and ShadingParameters).
The Dragonfly Model schema is designed to be extensible such that properties for various simulation engines can be assigned to building geometry. Schemas have been developed to extend the core Dragonfly Model for EnergyPlus/OpenStudio as well as Radiance. This section will focus on only describing the core Model schema in the absence of any extensions.
What Dragonfly lacks in terms of fine geometric detail, it makes up for in objects that help organize and edit building-scale properties. Altogether, Dragonfly Models are composed of 5 geometry objects. In order of most coarse/abstract to most fine/detailed, these objects are
- Building
- Story
- Room2D
- RoofSpecification
- ContextShade
The relationships of these objects are as follows:
The coarsest object in the Dragonfly Model schema is the Building, which typically maps to an entire Model when translated for energy or radiance simulation workflows. Buildings are composed of Stories that represent individual floors of the building. Stories are composed of Room2Ds, which map to individual zones in energy simulation workflows and map to the Rooms of the Honeybee schema. Story objects have multipliers, which can be used to represent cases where the same floor is repeated several times over the height of a Building. Story objects can also optionally have a RoofSpecification assigned to them, which is used to shape the tops of the 3D Room volumes generated from the Room2Ds. RoofSpecifications are composed of a list of planar 3D geometries and can take virtually any shape as long as these geometries lie above (and not below) the Room2D geometry of the Story they are assigned to. Lastly, ContextShades are also represented as planar 3D geometries and they can be represented with either a mesh (aka. Mesh3D) or individual planar geometries (aka. Face3Ds).
Both Buildings and ContextShades can be assigned to Dragonfly Models with the Buildings representing the simulation geometry and ContextShade representing objects like trees, terrain, monuments and other objects that might shade the simulation geometry. Shades attached to the building geometry are customarily represented with ShadingParameter objects that can be assigned to Room2Ds. However, there is nothing that prevents the use of ContextShade objects for this purpose.
The relationship between Dragonfly objects in 3D space can be visualized as follows:
