Object Relationships The interface in ECOTECT is based on a comprehensive relational CAD system that exploits a simple set of inherent relationships between building elements to greatly simplify both the modelling and editing process. Establishing relationships between objects is mostly automatic, however, you will also link and unlink objects manually as you refine your model.

Object relationships in ECOTECT are mostly for modelling convenience. If the inter-object relationships get in the way when you are editing your model, you can easily unlink the offending objects. The only inter-object link that is actually important to both the model and the analysis routines is the child PANEL link described below and used for inserting apertures in larger objects. All other linking is purely optional.

Some Common Relationships When certain objects are created, relationships with other objects are automatically established. The following are two of the most common examples of this. You can unlink any of these objects at any time. However, for a WINDOW to actually represent a hole in a WALL, the two objects must be be linked. Otherwise they will simply share the same 3D plane in space and will generate a warning during inter-zonal calculations.

Child PANEL

Child PANEL objects exist within the bounds of their parent. They represent a hole in the parent object and therefore will only move inside it's defined plane boundary. Their surface area is subtracted from the total surface area of the parent. If adjacent to another planar element on a different zone, they are assumed to be a hole through both surfaces (though this will not be visible, especially in the OpenGL view and when displaying deeply penetrating shadows).

Extruded Object

Extrusions are created when another object is extruded. The resulting child planes extend in the direction of the parent object's extrusion vector. The height of vertical elements can be edited, however the CEILING object will remain exactly offset from the original by the current vector.

The best way of changing an extrusion is to simply select the original object and then either change its extrusion vector in the Selection Information panel or re-extrude it using any of the interactive or parametric extrusion tools. The system is smart enough to work out not to create new child objects but to update existing extruded children, even if some of them have been deleted.

Apertures Without Relationship Linking It is possible to create an aperture within an object without using relationship linking. In this way, simply create the main object as if it were a closed letter C. Thus, you first trace around the outside of the WALL boundary in one direction and then trace the internal boundary in the opposite direction, as shown below. Then a completely unrelated and unlinked WINDOW object can simply be inserted in the hole.

Parent/Child Relationships All relationships are based on a standard parent/child hierarchy. Transforming a parent object transforms all of its children, whilst transforming a child is always independent of the parent. Almost all relational information is stored at node level. Thus, relationship types are defined internally as a combination of nodal restrictions.

The five basic nodal restrictions are as follows:

Locked: The node is locked to its parent node. It is fixed in position and cannot be moved unless the parent node is moved. Such nodes are highlighted in dark grey instead of the red used for editable nodes. Offset: The node is locked in a position relative to its parent node, offset by the parent object's vector. Like a locked node, it is also fixed in position and cannot be moved unless the parent node is moved and are also highlighted in dark grey instead of the red used for editable nodes. Vector: The node is restricted in movement to a line passing through its parent node and running along the extrusion vector of its parent object. Coplanar: The node is restricted in movement to the 3D plane defined by its parent object. When interactively selected and dragged, this node will only move within this plane. Internal: The node is restricted in movement such that it must always be inside the polygon defined by its parent object. This restriction is almost always used in conjunction with the COPLANAR tag and is applied to child objects such as WINDOWS and DOORS. Locked and offset nodes are highlighted in grey instead of red and cannot be interactively edited. All other nodes can be interactively edited or nudged. If the new position does violates any of the nodal restrictions, it will either not move into that position, or the entire object will turn red to indicate that a relationship violation has occurred.

Individual nodal relationships can be viewed and edited using the Selection Information panel. You can also unlink individual nodes by simply setting their type to EDITABLE.