Select Surface>Loft. Or type “loft” on the command line area. At the

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This tutorial covers a series of advanced modeling features. Some of the features are specific to Rhino, whereas

others appear as variations of tools in other modeling programs. The key exercises are to: (1) loft curves into surfaces,

(2) project curves to surfaces, (3) cap open faces, and (4) create a cage to change surfaces.

Lofting a Surface: The term “lofting” comes from the ship building industry. It is the method of placing a surface over

a ship skeleton. In Rhino, we generate a lofted surface over a series of curves spaced out. Thus, to loft a surface is to

create a series of splines and arrange them to define the soon to be formed surface.

Select Surface>Loft. Or type “loft” on the command line area. At the command prompt, click on the splines in

the correct order. Click Enter or Right Click when done. The following window will appear (Note, click to one side

of the three lines consistently to set the uniform direction of the loft). The following Loft Options box will appear.

Under the Style drop down you will have a number of loft options.

Normal: The most mathematically

efficient loft

Loose: Will create a smoother loft

that is not based exactly off the loft

curves, but averaged.

Tight: Constructs a loft that is exactly on the various loft curves

Straight Sections: Will create a series of ruled surfaces between loft

line.

Developable: Will create lofts that can be flattened out on a single

sheet.

Uniform: Guarantees that every control point affects the surface

exactly the same way.

S206E057 -- Lecture 8, 10/11/2023, Rhino Advanced Features – an overview

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This will create a closed lofted surface, check and click preview to see results.

Align Curves: This is used to flip the direction of a curve, an important modification.

Rebuild With XX Control Points. This allows to set a number of curve divisions

refining the smoothness of the surface.

Set the loft to rebuild with 20 points and click Preview to see the surface. If you like

it, click OK. Again, in Rhino 6 & 7, there is no “Preview” function, all actions done in

the view are run time (or real time) actions.

The lofted surface

Rebuilding Surfaces:

Often after you create a curve or surface, you will need to rebuild it. Rebuilding

a curve or surface changes the number of points in a curve or the number of

points in a profile curve used in creating a surface. Each point then has a line

(Iso-curve) running through it.

Rebuilding a curve or surface changes the number

of points in each line. This will in effect make the

curve or surface smoother (reducing points) or

more flexible (increasing curves)

Select a surface or curve, then click on

Edit menu > Rebuild

Change the number of points in both the U

and V Directions

Keep the Curve Degree to lower than 3

Click Preview to preview the new Curve or

Surface (U means X axis and V is Y axis.)

If the input is not deleted, a copy will be

generated. After it is finalized, then “Click OK”

to rebuild.

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Original Surface with 50 Control Points. Same Surface “Rebuilt” with only 6 control points

Trim and Split

When dealing with complex surfaces, you will most likely need to cut holes and trim surfaces. This can be done with

the Boolean tools, but there are times when they do not provide the level of detail that the trim and split tool offer.

Trim and Split is basically the same tool, the only difference is that the

trim tool will delete the piece being cut. Split will just cut the objects.

Trim Split

In this example, I have placed a cylinder through the lofted surface.

Click the Split tool

At the prompt, click on the lofted Surface, this is the object

to be split. Click Enter. Then Click on the Cylinder. This is

the object to cut.

Click Enter to split the object.

See the Object Split (Note: I deleted the cylinder)

The Trim Tool will automatically delete the cutting object. Also in this example, I just draw a circle shape in front of the

lofted surface. I do not need to extrude a cylinder through the lofted shape. Note: the circle is drawn on the Front view

port.

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Click on the Trim Tool

At the Prompt: Select Cutting Objects, choose the Circle

and hit Enter.

At the Prompt: Select object to Trim, select the lofted

surface.

NOTE: Do this through the Front Elevation, otherwise the

lofted shape would be cut through the perspective view.

Note: If you click on the lofted shape inside the circle, the

inside circle will be deleted. If you click outside the circle,

the outside will be deleted. Type Undo to undo it.

Trimmed by clicking inside the circle Trimmed by clicking outside the circle.

Duplicating and Projecting Curves onto Surfaces:

You can generate curves from existing geometry and then project that onto other geometries. In this example, I

have added a new plane (Rectangular Plane, corner to corner) to the back of the trimmed lofted surface. I am

going to project the holes onto the surface.

Surface to project the curve onto

Lofted Surface with the hole

Step One: Duplicate the Edge of the hole.

Click on Curve>Curve From objects>

Duplicate Edge (DupEdge)

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At the Command Prompt, select the edge to duplicate. Note:

Sometimes you will have to click on many segments of an edge to

duplicate. If this is true, you will also need to join the segments after

they are duplicated into one singe curve.

Duplicated edge

It is important to duplicate the edge for

projection, instead of projecting the original

edge (the circle) to the back surface.

Step Two: Project the duplicated edge curve onto the surface.

Select Curve>Curve From Objects> Project.

At the Command Prompt, Select Surfaces...to project onto, select the

surface. NOTE: You have to do this through an orthogonal view. If you

do it in perspective view, it will project the curve or miss it.

Click the Surface to project onto in an orthogonal view.

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The curve projected onto the

surface. Delete the surface

and you are left with the

projected curve.

I also drag the “original circle”

further to the front of the lofted

surface, modify its orientation,

size, and loft these two circles.

Lofted Surface

Filleted Surfaces

I lofted the two Edge curves

and filleted the intersection

of the two lofted surfaces

(the back and the front one)

to make a composition.

Capping Holes and Generating Surfaces from Edge Curves:

Often you will need to cap holes. If the curves that make up the edge of the hole are planar. (They all fall inside a single

plane -- you can also use the Planar Holes tool.)

Select Surface > Planar Curves (or type planarsrf)

Select the curves to cap and hit Enter. (Note: can select more than one curve.)

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To cap a non-planar surface, you will need to use the Surfaces > Edge Curves (or edgesrf) tool. The problem

with the edge curve tool is that there is a limit to the number of curves you can select (only 2-4 curves). To get

around this you can join additional curves. However, the result can be less than satisfactory.

A common use for the Surface from edge curves is to box out two surfaces.

We will use this tool to create surface along the two edges of this

surface. (Note: We could loft it but it is hard to do it on all four sides.)

Step One: Snap Curves between the two Surfaces.

Use the curve (or line, or polyline) tool, and with the end point O-Snap active and Project off, snap two lines

between the two surfaces for generating lines connecting surfaces.

Two Curves (in this case, they

are lines) drawn between the

two surfaces.

Step Two: Activate the Edge

Curves tool by Clicking on

Surface>Edge Curves

Select the 2 Curves and

2 Edges that will make

up the surface.

The surface is created.

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Model with all four surfaces created, see the left and middle images. The right image has two curves of the top and bottom

to generate a curved surface. If your building model has extruded form with four edges, you could use this method to create

the form, see the image in the middle. Surfaces could also be offset by offsetsrf function with a distance and the

Corner=Round, as shown on the lower right image.

Object Manipulation using Caging:

Caging allows you to transform a complex object using a small number of edit

points.

Caging is a two-step process, first you define the shape (Cage) that will be used

to box around the object and transform.

To do this select Transform>Cage Editing>Create Cage

At the prompt, draw a 3-point box around the object and hit Enter. A box is

formed around the object. The next step is to Edit the Cage which will transform

the object.

Click Cage Edit.

At the prompt, Select Captive Objects, select the objects to trans-form.

Use window selection to select the entire form.

At the next Prompt, Select Control Object, select the caged box. At the

next Prompt, select Global, and points are created throughout the cage.

This function is finished.

Select Points in the cage and move the points up/down.

Transformed Object

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Another example:

This exercise explains some Rhino tools for organic form modeling. Hope you did learn the various methods for

constructing models. Of course, there are many methods that could serve the same purposes to achieve similar

results. You have to explore more on your own.

The way to take the cage away is to hit ESC key to make the control points disappear, then delete the frame

from the scene.

Other examples of using cage to modify the form

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One rail sweep algorithm example:

Draw a curve. Lift up control point. Lift up control point.

Lift up control point. Completed lift up curve. Draw a handrail profile

Array the profile along the curve. One rail sweep. Offsetsrf