Array Along a Curve in Rhino 8: ArrayCrv and Surface Guide

Rhino 8’s official help documentation describes ArrayCrv and ArrayCrvOnSrf as commands for repeating an object along a curve or a curve on a surface. ArrayCrv creates copies along a selected path curve, while ArrayCrvOnSrf places and rotates objects along a curve on a surface. This guide covers the steps and options for both commands in Rhino 8, within the limits stated in the product documentation.

When to use each command

ArrayCrv distributes objects along a curve selected as the path. It can be used for curve-based arrays, such as elements repeated along a line in an architectural model. You can specify either the number of copies or the distance between them. For the item count, enter a value of 1 or greater; when you specify a distance, the curve’s length determines how many items fit.

ArrayCrvOnSrf is intended for cases where the path curve lies on a surface. Objects are placed and rotated along the curve, with their orientation determined by the surface normal. That means the selected surface, as well as the curve itself, is part of the operation.

Arraying along a curve with ArrayCrv

1. Select the objects to array. The command copies the selected objects along the path curve.

2. Select the path curve near the end where you want the array to begin. If the object is not on the curve, use the Basepoint option to set its starting position.

3. Specify the number of items or the distance between them. You can enter an item count of 1 or greater. When you specify a distance, the number of items depends on the curve’s length.

4. Control how the objects are oriented along the curve. Choose the appropriate orientation behavior for your model from the options below.

The command’s menu path is listed as Array › Transform › Array > Along Curve. In the command line, Items refers to the item count, while Distance refers to the spacing between items. To use only part of a curve as the path, type SubCrv when selecting the curve.

The orientation options change how the copied object responds to bends in the curve:

• NoRotation copies the object to different positions without applying roll, pitch, or yaw.

• Freeform allows the object to follow all three rotations at once.

• Roadlike applies pitch and yaw but not roll; the y-axis remains parallel to the selected view’s CPlane.

• Stairlike applies yaw only; the x- and y-axes remain parallel to the selected view’s CPlane.

• Roll, Pitch, and Yaw specify rotation around the x-, y-, and z-axes, respectively.

These option names help you choose a rotation behavior; the right choice depends on the shape of the object and the curve. Since the documentation does not recommend a specific orientation for any particular architectural use, choose the appropriate option based on the result.

ArrayCrvOnSrf for a curve on a surface

1. Select the objects to array and specify a starting point. The documentation notes that this point is usually on the object being copied.

2. Select the path curve near the beginning of the array, then select the surface.

3. Position the objects along the curve. Specify their placement by selecting on the curve or entering a distance from the last position.

4. Use Divide to define the number of objects and Multiple to set the spacing between them. If you need to use only part of the curve, select a section with SubCrv.

The command’s menu path is Array › Transform › Array > Along Curve on Surface. The key difference is that object orientation is determined by the surface normal. Selecting a surface is therefore a required part of the command workflow, and placement on the curve is evaluated in the context of that surface.

Use in architectural and visualization workflows

For architects, interior designers, and visualization specialists, these commands make it possible to build object arrays tied to a curve directly in the model. When arraying along a curve, choosing a count or spacing determines how the array is defined. With the surface-based method, the surface normal affects object orientation. For that reason, a flat path and a path on a surface should not be treated as the same command workflow.

Clarifying the starting end and the object’s reference point before arraying makes placement easier to control. If the object is not on the curve, consider using Basepoint; if you do not want to use the entire curve, consider selecting a section with SubCrv. In internal workflows, it is important to check that the commands and options match the names used in the Rhino 8 documentation. The source documentation provides no information about hardware requirements, licensing terms, or compatibility with other software, so no specific requirements should be assumed on those matters.

Common mistakes

• Treating ArrayCrv and ArrayCrvOnSrf as the same operation: the second command involves selecting a surface and a curve on that surface.

• Overlooking the starting direction: select the path curve near the end where you want the array to begin.

• Failing to specify a reference point when the object is not on the curve: in this case, Basepoint can be used to define the starting placement.

• Not checking the orientation option: NoRotation, Freeform, Roadlike, and Stairlike produce different rotation behaviors.

• Confusing Distance with Items: the former specifies spacing, while the latter specifies the item count.