Selecting Objects in Rhino 8: A Practical Guide to Windows, Lasso, and Sub-Objects

Rhino 8 offers window, crossing, lasso, and brush selection tools, as well as methods for selecting sub-objects such as faces, edges, and control points. The options described in McNeel’s Rhino 8 help documentation make it easier to isolate the right geometry in architectural modeling and visualization scenes. The steps below focus on choosing a selection method based on the object’s position and the selection area.

1. Use window and crossing selection correctly

Click an object to select it by itself. To clear the selection, click a point away from the objects. When selecting multiple objects with a rectangular area, the drag direction matters:

1. Drag from left to right: Window selection picks objects fully inside the selection rectangle. Objects that cross the boundary aren’t selected with this method.

2. Drag from right to left: Crossing selection picks objects inside the area, as well as objects that partially intersect the rectangle. This can return a broader selection in a busy view.

3. Add to or remove from the selection: Hold Shift and click, or draw a window/crossing area, to add objects to the selection. Doing the same with Ctrl (CMD on Mac) removes selected objects.

To use a command for rectangular selection, enter:

SelWindow

For crossing selection, enter:

SelCrossing

The standard shortcuts listed in the documentation are W and C, respectively. To configure mouse behavior to always use window or crossing selection, check the Mouse group select option under Mouse Options. To change the rectangle’s color, look for the SelectionWindowStrokeColor and SelectionWindowFillColor settings under Tools > Options > Advanced. The crossing rectangle color settings are listed as SelectionWindowCrossingStrokeColor and SelectionWindowCrossingFillColor.

2. Use lasso, brush, and boundary selection for irregular areas

When a rectangular area also captures surrounding geometry, it can help to choose a selection method that better fits the model view.

1. To select objects within an irregular outline, use the lasso to draw around them. The lasso’s Window option selects objects fully inside the outline; Crossing includes objects intersected by the boundary or fully inside it. Undo removes the last point in the path.

2. Use brush selection to gather objects along a wide stroke. The default behavior is crossing selection, so objects touched by the brush stroke are selected. You can set the brush width in pixels. Hold Shift and move the cursor up or down to change the brush size dynamically.

3. To use a closed curve as a selection boundary, enter:

SelBoundary

With this tool, Window selects objects fully inside the boundary, while Crossing selects objects fully inside or intersecting it. When Precise = Yes, the tool uses the wireframe curve as the boundary and performs the evaluation in screen coordinates using double-precision floating-point calculations; even a small part of an object outside the boundary means it won’t be selected. With Precise = No, it uses a bitmap selection mask; according to the documentation, this can create a tolerance zone about half a pixel wide around the boundary.

The rectangular selection tool and brush both have a SelectThroughObjects option, which controls whether objects behind other geometry are included in the selection. With RealTimeSelection enabled for the brush, objects are selected as the brush circle touches them. When disabled, selection is applied after the command finishes.

3. Isolate sub-objects and overlapping geometry

On surfaces, polysurfaces, meshes, and SubDs, you may sometimes need only an edge, face, or control point rather than the entire object. To select a sub-object, hold Ctrl (CMD on Mac) + Shift and click, or draw a window/crossing area. To deselect a sub-object, use Ctrl (CMD on Mac) and click or make an area selection.

When objects overlap beneath the cursor, Rhino may open a selection menu. Click the name of the object you want in the list; you can move between items with the mouse wheel or by clicking the initial selection point again. Right-click to accept the currently highlighted object. This can help reduce the chance of selecting the wrong object when surfaces are close together.

There is an important limitation with blocks: objects inside a block can be selected as whole objects, but faces and edges inside the block cannot be selected. Nor can you select all objects and sub-objects inside nested blocks. Also, selecting before a command starts doesn’t always produce the same result as selecting after it begins. Depending on the command’s object input requirements, preselected geometry may be accepted, produce an unexpected result, or be cleared so the command can prompt for a new selection.

4. Verify the selection and inspect object information

To select all objects, enter:

SelAll

The documented shortcut is Ctrl (CMD on Mac) + A. To clear the selection, enter:

SelNone

The shortcut for this command is listed as Esc; however, it cannot be used to clear previously selected objects while a command is running. To check an object’s type or layer after selecting it, run:

What

and select the object. A separate window displays information such as object type, object ID, layer name, render material, and its source. For more detailed technical data, the List command reports internal structure; McNeel describes it as a tool generally used for debugging.

What does this offer for architectural and visualization workflows?

An architectural model may contain multiple surfaces, edges, and blocks in the same area. Crossing, lasso, or brush selection can be useful for quickly gathering these groups, but their broad scope means you should check the result. When working on a single surface boundary or sub-object, window selection and Ctrl + Shift sub-object selection offer a more controlled approach.

Teams should pay particular attention to the limitations with blocks and the behavior for selecting hidden objects. Overlapping geometry can be separated using the selection menu, and What can confirm the selected object’s layer and material. The documentation doesn’t specify any special hardware requirements for selection, so the key is to match the selection mode to the geometry in the model and account for differences between selecting before and after a command starts.

Common mistakes

• Dragging a window from left to right and assuming it will also select objects that intersect the boundary; drag from right to left for crossing selection.

• Trying to select faces or edges inside a block; the documentation states that only whole objects inside blocks can be selected.

• Not checking how objects behind other geometry are treated in rectangular or brush selection; review the SelectThroughObjects setting.

• Assuming you can use SelNone to clear preselected objects while a command is running; the documentation says this isn’t supported during a command.