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User Interface Selection Methods

Introduction​

The Revit API offers a robust set of tools for selecting and interacting with elements in a Revit model. This comprehensive guide explores various selection methods, providing detailed examples and explanations to help you master element selection in your Revit API scripts.

Required Libraries and Setup​

Before we begin, let's ensure we have all the necessary libraries imported and set up our document references:

import clr
clr.AddReference('RevitAPIUI')
import Autodesk
from Autodesk.Revit.UI import *
from Autodesk.Revit.UI.Selection import *

clr.AddReference('RevitServices')
import RevitServices
from RevitServices.Persistence import DocumentManager

# Get the current document and UI document
doc = DocumentManager.Instance.CurrentDBDocument
uidoc = DocumentManager.Instance.CurrentUIApplication.ActiveUIDocument

This setup provides access to the Revit API, the current document, and the user interface, which are essential for performing selections.

1. Basic Element Selection​

1.1 Pick a Single Element​

The PickObject() method is the foundation of element selection in Revit API. It prompts the user to select a single element in the Revit interface.

Example:

try:
    selected_reference = uidoc.Selection.PickObject(ObjectType.Element, "Select an element")
    element = doc.GetElement(selected_reference.ElementId)
    print(f"Selected element: {element.Name}")
    print(f"Category: {element.Category.Name}")
    print(f"ID: {element.Id}")
    
    # Get some basic parameters
    for param in element.Parameters:
        print(f"{param.Definition.Name}: {param.AsValueString()}")
except Exception as e:
    print(f"Selection cancelled or failed: {str(e)}")

This example not only selects an element but also retrieves and prints various properties and parameters of the selected element.

Exercise: Modify the code to allow selection of a specific category (e.g., only walls). Hint: You'll need to use a custom ISelectionFilter.

1.2 Pick Multiple Elements​

When you need to select multiple elements, the PickObjects() method comes in handy.

Example:

try:
    selected_references = uidoc.Selection.PickObjects(ObjectType.Element, "Select multiple elements")
    elements = [doc.GetElement(ref.ElementId) for ref in selected_references]
    
    category_count = {}
    for elem in elements:
        category = elem.Category.Name
        category_count[category] = category_count.get(category, 0) + 1
    
    print(f"Selected {len(elements)} elements")
    for category, count in category_count.items():
        print(f"{category}: {count}")
except Exception as e:
    print(f"Selection cancelled or failed: {str(e)}")

This example selects multiple elements and provides a summary of the selected elements by category.

Exercise: Extend the code to calculate and print the total volume of all selected elements that have a volume parameter.

2. Advanced Selection Techniques​

2.1 Selection by Rectangle​

The PickElementsByRectangle() method allows for a more visual selection process, similar to dragging a selection box in the Revit interface.

Example:

try:
    selected_elements = uidoc.Selection.PickElementsByRectangle("Select elements by rectangle")
    
    levels = {}
    for elem_id in selected_elements:
        elem = doc.GetElement(elem_id)
        if hasattr(elem, 'Level'):
            level_name = elem.Level.Name if elem.Level else "No Level"
            levels[level_name] = levels.get(level_name, 0) + 1
    
    print(f"Selected {len(selected_elements)} elements")
    for level, count in levels.items():
        print(f"Level {level}: {count} elements")
except Exception as e:
    print(f"Selection cancelled or failed: {str(e)}")

This example selects elements within a rectangle and organizes them by level, providing a count of elements on each level.

Exercise: Modify the code to filter the selected elements, keeping only those with a specific parameter value (e.g., comments containing a certain keyword).

2.2 Pick Box​

The PickBox() method creates a selection box based on two points, which can be useful for defining a 3D region for selection or other operations.

Example:

from Autodesk.Revit.DB import BoundingBoxIntersectsFilter, Outline

try:
    box = uidoc.Selection.PickBox(PickBoxStyle.Enclosing, "Select area")
    outline = Outline(box.Min, box.Max)
    bb_filter = BoundingBoxIntersectsFilter(outline)
    
    collector = FilteredElementCollector(doc).WherePasses(bb_filter)
    elements = list(collector)
    
    print(f"Found {len(elements)} elements within the picked box")
    category_count = {}
    for elem in elements:
        category = elem.Category.Name if elem.Category else "No Category"
        category_count[category] = category_count.get(category, 0) + 1
    
    for category, count in category_count.items():
        print(f"{category}: {count}")
except Exception as e:
    print(f"Selection cancelled or failed: {str(e)}")

This example uses the picked box to create a bounding box filter, then finds all elements that intersect with this box. It provides a summary of the elements found, categorized by their Revit category.

Exercise: Extend the code to calculate the total surface area of all walls within the picked box.

3. Filtered Selection​

3.1 Custom Selection Filter​

Custom selection filters allow for fine-grained control over which elements can be selected.

Example:

class CustomFilter(ISelectionFilter):
    def __init__(self, category_name, parameter_name, parameter_value):
        self.category_name = category_name
        self.parameter_name = parameter_name
        self.parameter_value = parameter_value
    
    def AllowElement(self, elem):
        if elem.Category and elem.Category.Name == self.category_name:
            parameter = elem.LookupParameter(self.parameter_name)
            if parameter and parameter.AsString() == self.parameter_value:
                return True
        return False
    
    def AllowReference(self, reference, point):
        return False

try:
    custom_filter = CustomFilter("Walls", "Comments", "Important")
    selected_elements = uidoc.Selection.PickObjects(ObjectType.Element, custom_filter, "Select important walls")
    
    print(f"Selected {len(selected_elements)} important walls")
    for ref in selected_elements:
        elem = doc.GetElement(ref.ElementId)
        print(f"Wall ID: {elem.Id}, Name: {elem.Name}")
except Exception as e:
    print(f"Selection cancelled or failed: {str(e)}")

This example creates a custom filter that only allows selection of walls with a specific comment. It demonstrates how to combine category filtering with parameter value checking.

Exercise: Create a filter that allows selection of either doors or windows, but only if they are hosted by a wall that has a fire rating parameter.

4. Working with Selected Views​

Retrieving and working with selected views in the project browser can be very useful for batch operations or reporting.

Example:

def get_selected_views():
    selected_ids = uidoc.Selection.GetElementIds()
    selected_views = [doc.GetElement(id) for id in selected_ids if doc.GetElement(id).GetType().Name.startswith("View")]
    return selected_views

selected_views = get_selected_views()
print(f"Selected {len(selected_views)} views")

for view in selected_views:
    print(f"View Name: {view.Name}, Type: {view.ViewType}")
    
    # Count visible elements in each view
    collector = FilteredElementCollector(doc, view.Id).WhereElementIsNotElementType()
    element_count = collector.GetElementCount()
    print(f"  Visible elements: {element_count}")
    
    # Check view-specific properties
    if hasattr(view, 'Scale'):
        print(f"  Scale: 1:{view.Scale}")
    if hasattr(view, 'ViewRange'):
        top_level = view.GetViewRange().GetLevelId(PlanViewPlane.TopClipPlane)
        top_level_name = doc.GetElement(top_level).Name if top_level != ElementId.InvalidElementId else "Not Set"
        print(f"  Top Clip Plane: {top_level_name}")

This example retrieves all selected views, regardless of their type, and provides detailed information about each view, including the number of visible elements and view-specific properties.

Exercise: Extend the function to create a dictionary where the keys are view types and the values are lists of view names of that type. Print a summary of how many views of each type are selected.

5. Point Selection​

Point selection is crucial for many operations, such as creating new elements or measuring distances.

Example:

from Autodesk.Revit.DB import XYZ

def pick_points(prompt, count):
    points = []
    for i in range(count):
        try:
            point = uidoc.Selection.PickPoint(ObjectSnapTypes.Endpoints, f"{prompt} (Point {i+1}/{count})")
            points.append(point)
        except Exception as e:
            print(f"Point selection cancelled or failed: {str(e)}")
            return None
    return points

def distance_between_points(p1, p2):
    return p1.DistanceTo(p2)

points = pick_points("Select two points to measure distance", 2)
if points and len(points) == 2:
    distance = distance_between_points(points[0], points[1])
    print(f"Distance between points: {distance:.2f} feet")
    
    # Create a line element between the two points
    try:
        line = Line.CreateBound(points[0], points[1])
        doc.Create.NewDetailCurve(doc.ActiveView, line)
        print("Created a detail line between the points")
    except Exception as e:
        print(f"Failed to create detail line: {str(e)}")

This example demonstrates how to pick multiple points, calculate the distance between them, and even create a detail line in the active view based on the selected points.

Exercise: Modify the code to pick three points and calculate the area of the triangle formed by these points.

6. User Interaction with TaskDialog​

Creating interactive dialogs enhances the user experience and allows for more complex decision-making in your scripts.

Example:

def create_task_dialog(title, main_instruction, content, commands, verification_text=None):
    dialog = TaskDialog(title)
    dialog.MainInstruction = main_instruction
    dialog.MainContent = content
    
    for command in commands:
        dialog.AddCommandLink(command[0], command[1])
    
    if verification_text:
        dialog.VerificationText = verification_text
    
    return dialog

# Usage example
commands = [
    (TaskDialogCommandLinkId.CommandLink1, "Option 1: Do something"),
    (TaskDialogCommandLinkId.CommandLink2, "Option 2: Do something else"),
    (TaskDialogCommandLinkId.CommandLink3, "Option 3: Cancel operation")
]

dialog = create_task_dialog(
    "Important Decision",
    "Please choose an option",
    "Your choice will affect the following operations.",
    commands,
    "Remember my choice"
)

result = dialog.Show()

if result == TaskDialogResult.CommandLink1:
    print("User selected Option 1")
elif result == TaskDialogResult.CommandLink2:
    print("User selected Option 2")
elif result == TaskDialogResult.CommandLink3:
    print("User cancelled the operation")

if dialog.WasVerificationChecked():
    print("User wants to remember this choice")

This example creates a more complex TaskDialog with multiple command links and a verification checkbox. It demonstrates how to create reusable dialog functions and handle various user responses.

Exercise: Create a TaskDialog that asks the user to choose a category of elements to select (e.g., Walls, Doors, Windows). Based on the user's choice, use the appropriate selection method to select elements of that category and display a count of selected elements.

Conclusion​

This expanded guide covers a wide range of Revit API selection methods, from basic element picking to advanced filtered selections and user interactions. The additional examples and exercises provide a deeper understanding of how these methods can be applied in real-world scenarios.

Remember, the key to mastering Revit API selection is practice and experimentation. Try combining different methods, create your own custom filters, and always consider the user experience when designing your scripts.

As you become more comfortable with these selection techniques, you'll be able to create more sophisticated and efficient Revit add-ins and scripts, enhancing your productivity and capabilities in Revit development.