In brief
- A left-to-right selection window selects objects entirely inside the rectangle; a right-to-left selection also includes objects touched by the rectangle.
- Use Ctrl (CMD on Mac) + Shift to select sub-objects such as faces and edges.
- Check reports errors in an object's data structure; SelBadObjects selects objects that fail the Check test.
- Passing the Check test does not mean an object is flawless in every respect.
What will you learn in this tutorial?
Selecting objects in Rhino involves more than simply clicking one. In a large model, you may need to find the right object, distinguish items that are hidden or overlapping, or work with just one edge of a surface. Choosing the selection method that fits the task helps reduce the risk of working on the wrong geometry.
In this tutorial, you’ll learn how to use Rhino 8 selection methods such as rectangular window, crossing, lasso, and brush selection; select sub-objects; and then inspect potential structural issues in a model with the Check and SelBadObjects commands. These checks can help assess a model’s condition, particularly after editing or file transfer. However, don’t assume an automated check will catch every type of geometric flaw.
Requirements
Rhino 8 must be installed. The commands and selection behaviors below are described in the official Rhino 8 user guide.
The sources do not specify an account requirement. The tutorial also does not describe the use of a new plug-in or additional tool.
The model you want to check must be open. Using a model with multiple objects will make it easier to try the selection methods; this is a practical suggestion, not a software requirement.
You can start commands from the command line or use the selection and diagnostic tools described in the guide. In the steps below, enter the command names for this version exactly as written.
Step by step: selecting objects and sub-objects
1. Select one object and clear the selection
Click an object to select it. To deselect, click an empty area away from the objects. When multiple objects are selected, the SelNone command clears the selection; the guide also lists Esc as a shortcut for this command. SelAll selects all objects, and its shortcut is Ctrl (CMD) + A.
When testing selection behavior, start by selecting one object, then click an empty area to confirm that it is deselected. This simple check helps prevent a previous selection from carrying over to the next command. Whether a command uses objects that were already selected depends on the command: some accept the current selection, while others prompt you to select objects again.
2. Use direction with rectangular selection
When you drag the selection rectangle from left to right, only objects entirely inside the rectangle are selected. Dragging from right to left performs a crossing selection: in addition to objects inside the rectangle, objects partially intersected by its boundary may also be selected.
Try both methods in a crowded viewport. Use left-to-right selection when you want to target only objects fully enclosed by the rectangle; use right-to-left selection when you also want to include objects that touch a particular area. The SelWindow and SelCrossing commands also provide window and crossing selection, respectively, from the command line.
3. Select a freeform area with a lasso or brush
When a regular rectangle isn’t suitable, Lasso lets you select objects by drawing an irregular shape. With a lasso, Window selects only objects fully inside the shape, while Crossing selects objects inside or intersecting it. The guide also lists the Undo option for undoing the last point of the lasso while drawing.
The SelBrush command selects along a thick brush stroke. By default, it uses crossing selection to select objects touched by the stroke. BrushWidth sets the brush width in pixels; you can also change its size during selection by holding Shift and moving the cursor up or down. When the RealTimeSelection option is on, objects are selected as soon as the brush touches them. If the wrong objects are included with these tools, check the selection type and brush width again.
4. Find the right object among overlapping objects
If several objects overlap beneath the cursor and Rhino can’t determine which one you want to select, the Selection Menu may appear. Choose the object you want from the list, or left-click at the cursor location to move through the listed objects. The mouse wheel also moves through the list; right-click to accept the currently highlighted selection.
When you need to select an object behind a surface or another object, note that the SelectThroughObjects option in the selection tool determines whether hidden objects behind other objects can be selected. Before using this option, check that the intended object is actually selected.
5. Select part of an object instead of the whole object
Sub-object selection lets you work with parts such as surfaces, edges, faces, and vertices. Before selecting, or after a command has started, hold Ctrl (CMD) + Shift and click or make a window/crossing selection to select sub-objects with the mouse. To deselect sub-objects, use Ctrl (CMD) with a click or area selection.
Blocks have one limitation: objects inside a block can be selected as a whole, but faces or edges inside the block cannot be selected. In nested blocks, you also cannot select the inner objects or sub-objects. If the selection result is unexpected, consider whether the geometry is inside a block.
6. Inspect geometry with Check
Select the object you want to check and run the Check command. It reports errors in the selected object’s data structure. If there are multiple objects, checking them individually can make it easier to identify which geometry the report refers to.
To find objects in the model that fail the Check test, use the SelBadObjects command. It selects all objects that fail Check. If an object is reported as problematic, the guide recommends deleting or rebuilding it. Make your decision in the context of the model and the object’s role in the project; don’t delete geometry indiscriminately without reviewing the check report.
Common mistakes
Overlooking the selection direction: Left-to-right and right-to-left selection do not produce the same result. With the first, an object must be entirely inside the rectangle; with the second, partial intersection may also select it.
Ignoring objects that aren’t visible: Hidden or obscured objects can affect the result of crossing selection or the
SelectThroughObjectsbehavior. If needed, check the selection filters and options.Selecting the whole object instead of a sub-object: To target a face or edge, use
Ctrl (CMD) + Shift. Also keep in mind that sub-objects inside blocks cannot be selected.Treating the Check result as a guarantee: Check examines the general object structure; passing the test does not prove that the object is 100% correctly configured. Some issues, such as surfaces that fold back onto or intersect themselves, may not be detected automatically.
Ignoring small edges: The Rhino guide notes that very small edges and trimming edges that loop back on themselves can cause modeling problems. Avoid unnecessary small edges when creating geometry, and try to keep edge matching between adjacent parts clean.
Next steps: impact on architecture and visualization workflows
In architectural modeling, interior design, and visualization, accurate selection matters when editing a surface, separating elements in a model, or inspecting problematic objects. Window, crossing, lasso, and brush methods can help you select target geometry more carefully in models of varying complexity. Check and SelBadObjects can help inspect geometry before delivery, editing, or file transfer; they are not a guarantee that every model issue will be caught.
In your next project, compare the selection methods on the same model and assess the Check report in relation to specific objects in the model. The Rhino 8 guide also describes the CheckNewObjects command, which reports newly created bad objects during import. This command can report when new bad objects are created while reading a file or running a Rhino command. If you receive such a notification, noting which command was running and which objects were used can make it easier to investigate the issue.
Sources and license
This tutorial has been adapted into Turkish based on information in McNeel’s official Rhino 8 user guide pages “Selection commands” and “Check.” Both sources list the license information as “free.”
Sources
2 sourcesSource texts are not republished; short quotes are marked, everything else is our own summary and commentary.
For offices and students, the practical value of this workflow is that it helps identify target geometry more precisely through different selection methods and makes it quicker to start inspecting problematic objects. Especially in dense models, options such as lasso and brush selection mean you don’t have to rely solely on rectangular selection.
The steps here are based on commands documented in the Rhino 8 guide; the sources do not mention additional hardware or costs. It’s important to remember that Check does not catch every type of flaw. Its report should therefore be treated as one part of a geometry-checking process, not as standalone confirmation that the entire model is error-free.
Frequently asked questions
What is the difference between left-to-right and right-to-left selection in Rhino?
Left-to-right window selection selects objects entirely inside the rectangle. Right-to-left crossing selection also includes objects inside or partially intersected by it.
How do you select sub-objects such as faces or edges in Rhino 8?
While selecting with the mouse, hold Ctrl (CMD on Mac) and Shift, then click or use window/crossing selection. Sub-objects inside a block cannot be selected.
Does Rhino’s Check command find every error in a model?
No. Check reports errors in the selected object’s data structure, but passing the test does not mean the object is completely flawless. Some surface defects may be difficult to detect automatically.
