Create Section Curves with Contour and Section in Rhino 8

What you’ll learn in this guide

In Rhino 8, use Contour to create section lines at regular intervals along a model, or Section to create a section from a specific plane. Both commands generate planar outputs where the selected objects intersect the cutting planes. Depending on the settings and geometry, these outputs can be curves, points, or hatches.

This guide covers which command to use for each task, the basic steps, and the options that affect the results. The final section also walks through common issues involving section direction, hatches, and object properties.

Requirements

• Software and version: These steps are based on McNeel’s Rhino 8 help documentation.

• Model geometry: You need objects to use with the Contour or Section command. The documentation does not specify a required object type or file preparation method.

• Account requirements: The help documentation does not specify account requirements for these commands.

• Construction plane: The section planes for both commands are created perpendicular to the current CPlane. Before running a command, check that the current construction plane is appropriate for the desired section direction.

1. Choose Contour or Section for the task

Contour is useful when you need multiple, evenly spaced sections through a model. The planes it creates are laid out in both directions from the specified starting point. To define the result, set a direction perpendicular to the planes and the distance between sections, in addition to the starting point.

Use Section to create a section on a single plane. Define the section plane with two points; it will be perpendicular to the current CPlane. This distinction makes it easier to select the right command before you begin: Contour for multiple regularly spaced sections, Section for a specific plane.

2. Create evenly spaced sections with Contour

1. Select the objects you want to section.

2. Run the Contour command from the command line.

3. Specify the base point for the starting section plane. The planes will extend in both directions from this point.

4. Set the direction perpendicular to the section planes.

5. Specify the distance between consecutive section planes. The planes create outputs where they intersect the objects.

Use the Range option to generate sections within a specific interval. The AssignProperties options control the properties of the output objects. ByCurrentLayer creates the results on the current layer with its properties; ByInputObject inherits the properties of the input objects.

Under Output, you can choose All or CurvesOnly. All allows curve, point, or hatch output. CurvesOnly does not create hatches; it limits the results to curves or points. Use GroupObjectsByContourPlane to group results on the same section plane.

3. Create a section on a single plane with Section

1. Select the objects to section.

2. Run the Section command from the command line.

3. Select two points to define the section plane. The plane will be perpendicular to the current CPlane.

4. Set the output and property options for the desired result.

ExtendSection determines whether the section plane extends beyond the selected points. For object properties, you can use the current layer with ByCurrentLayer or the input objects’ properties with ByInputObject. The All setting under Output can create curves, points, or hatches; CurvesOnly does not create hatches. Use GroupObjectsBySectionPlane to group objects created with the same section plane.

The Rhino 8 help documentation also notes that the Section command supports History. However, the documentation does not explain how to edit through History within the scope of this guide, so no additional steps for this feature are provided here.

4. Check for common issues and review the output

• Sections are not appearing in the expected direction: Keep in mind that Contour and Section planes are created perpendicular to the current CPlane. Check the section direction and construction plane.

• The Contour spacing is not as expected: Review the starting point, the direction perpendicular to the planes, and the distance between sections. Remember that the planes extend in both directions from the starting point.

• No hatch is created: Hatches are created only for closed sections and when the object’s section style settings allow it. No hatch is created if the object’s section style is set to By Clipping Plane.

• The output has no hatch: Check whether Output is set to CurvesOnly. This option disables hatch output.

• Object properties differ from what you expected: Under AssignProperties, check whether current-layer properties or the input object’s properties are selected.

Impact on architecture and visualization workflows

Contour can be used when section curves are needed at regular intervals through a model, while Section can create a single section on a specific plane. Architects, interior designers, and visualization teams can use existing geometry to create planar curves, points, or hatches when the required conditions are met.

Before adding either command to a workflow, check how the section direction relates to the CPlane and which properties the new objects will inherit. The help documentation does not specify hardware, license-type, or compatibility requirements for other software; verify these separately for the Rhino installation and project environment in use. When hatches are needed, closed sections and the section style settings are particularly important.

Next steps

Try Contour and Section separately on the same model to compare evenly spaced sections with a section on a single plane. Then change the Output and AssignProperties options to see how they affect the output type and properties. For multiple Contour planes, review the spacing and direction; for Section output, check the plane defined by the two points. These checks can help you determine which command is right for generating the desired planar results from a model.

Sources and licensing

This guide is adapted into English from McNeel’s Rhino 8 help documentation for the Contour and Section commands. The sources used are official product documentation provided as license=free; the content has not been reproduced verbatim, and the steps have been rewritten in original sentences.