Handling of Parameters

Introduction

Efficient handling of Revit parameters is one of the key features of Revit_Toolkit. It is possible thanks to RevitParameter BHoM wrappers that are being generated per each parameter of an element (and its type) on Pull and unwrapped on Push. RevitParameters are stored in dedicated fragments that are attached to the BHoM object correspondent with the Revit element. For full control over what is pulled vs what is pushed, separate fragments for Pull (RevitPulledParameters) and Push (RevitParametersToPush) are used.

More details can be found in the next paragraphs, basic examples are available here and here.

Pulling Revit elements with parameters

As mentioned above, on Pull, the parameters of a Revit element get wrapped into RevitParameter objects, which are collected in RevitPulledParameters fragment attached to the BHoM object representing the element. Such parameters can be queried in two ways:

• all in one go using GetRevitParameters method
• value of a particular one using GetRevitParameterValue method

Pushing Revit elements with parameters

Out of the box, default parameter values will be assigned when creating a Revit element based on a BHoM object. This can be overwritten by setting the parameters to push (stored in RevitParametersToPush, as described in the first paragraph) with SetRevitParameter method. Similarly, when an existing element is updated on Push, only the parameters explicitly instructed to be overwritten (SetRevitParameter method) will change. Diagram below explains the process:

By default, when a Revit element gets updated, first its parameters are overwritten and then the location is updated. This means that if the user sets values to location-related parameters, the change may not take place due to being superseded by location update. To avoid that, it is possible to prevent the element's location from being updated by switching SetLocationOnUpdate property of RevitPushConfig to false .

Getting and setting parameter values in one diagram

The diagram below shows how to get or set the parameter values depending on whether they are type or instance.

Pushing new Parameter definitions

As mentioned in Conversion of Parameters and Identity Information paragraph, it is possible to create new Revit parameters (project or shared ones) by pushing a BH.oM.Adapters.Revit.Parameters.ParameterDefinition object.

Parameter mapping

Note: The concept of parameter mapping is complex to explain, but easy to use. Therefore, it is recommended to look at the examples here and here in order to capture the practicalities of it.

It may sometimes happen that different families have the same value stored under different parameter names. In such case, there is a need to map the values from more than one source into a single set. This can be done with the use of custom mapping settings that are part of Revit adapter settings.

MappingSettings object has a property named ParameterMaps that can contain parameter maps, each containing a set of ParameterLinks that define following relationships:

• relationship between the name of a Revit parameter and the name of a property of a BHoM object, to which its value will be assigned on Pull
• relationship between the name of a Revit parameter and the name under which the value will be stored in RevitPulledParameters on Pull
• the opposite to the first: relationship between the name of a property of a BHoM object, which value will be assigned to a given Revit parameter on Push
• the opposite to the second: relationship between the name under which the value is stored in RevitParametersToPush and the name of a Revit parameter to which it will be assigned on Push

If multiple Revit parameter names will be mapped into one name on the BHoM side:

• on Pull: first parameter found in the Revit element under one of the specified names will be copied over to the BHoM object
• on Push: the value originating from the BHoM object will be copied over to the first existing parameter found in the Revit element under one of the specified names

What is more, mapping can also be applied to type parameters, using ElementTypeParameterLinks.

Parameter maps are created per type, therefore a map specified for columns will not affect e.g. walls. The whole concept is mapped out in the diagram below.