Computer Aided Design
Introduction to Rhinoceros
The aim of this session is to introduce you to Rhinoceros (Rhino), which is a Computer Aided Design environment for building 3D models that we will be using in the first half of this course. Engineers, architects, jewellery designers etc. build 3D models to describe their intended, as-yet unbuilt designs. Typically, these models visualise how the object will look, captures measured dimensions as well as other relevant information. The precise description of its geometry is necessary for fabrication/construction. CAD software is usually differentiated into surface and solid modellers. Rhino belongs to the former, while CAD software like Solidworks (more commonly used in engineering) fall in the latter category.
We will first familiarise ourselves with the Rhino environment and principles of geometry creation and editing, and then complete some simple drawing tasks. This introduction aims to get you started with exercises in the upcoming sessions.
Navigation
Let’s begin by opening Rhinoceros and orienting ourselves to the default workspace.
Viewports
A large portion of the screen real estate is taken up by the viewport windows. By default Rhino shows 4 viewports: 3D perspective, top, front and right. These four views are synchronised. To demonstrate this, click on the perspective viewport to make it active and type ‘camera’, which is one of many available Rhino commands. The text appears at the command prompt (top of window) while you type. Hit enter and you are prompted to select further command option. Type s which is a shortcut (denoted as underlined character) for Show and hit enter to run the command. Note that the history of commands and options entered thus far is recorded above the prompt.
A camera widget appears in the Top, Front and Right viewports. It represents the camera for the active perspective viewport. Displayed as a trapezoid, the widget shows the camera viewpoint, its field of vision and the target location. The dotted part of the trapezoid describes the viewing frustum, which is the region of space visible in the perspective view.
Mouse Navigation
Next let’s learn to navigate using the mouse. Click and hold onto the right mouse button in order to rotate.
Note that the camera widget updates synchronously in the other 3 viewports by rotating around its target point. Hold shift together with the right mouse button to pan. Once again the widget updates and moves (or what we term translates) in the other views. Finally zoom in and out using the mouse scroll wheel. Alternatively, hold ctrl and the right mouse button together and drag the mouse up or down to zoom.
Enter camera command and hide option to stop displaying the widget. You may also hit F6 which is a keyboard shortcut assigned for toggling the camera on/off.
Menu, Toolbars and Panels
The menu bar is located at the top under the title bar. It contains most of the essential functions in Rhino. One way you can enter commands is by selecting the appropriate item from the drop-down menu. The Rhino file that we are working on right now is called a document and we can set its properties from the File menu. Rhino help documentation can also be accessed via the menu or by simply hitting F1.
The toolbar is positioned below the menu bar and contains graphical icons (grouped by functionality) for initiating commands. Not all the toolbars are visible by default. If you right click in the toolbar area, there is an option to show additional toolbars via checkboxes. To demonstrate using the toolbar, we are going to change our viewport layout and maximise just the Top view. Click on the Standard toolbar and locate the icon which shows 4 viewports. Cascade the other items by either clicking and holding the mouse button or by clicking on the lower triangle. Find the icon showing one viewport and press it to maximise the currently active viewport. To return to the default layout, click the 4 viewport icon once more.
The sidebar is located to the left of the viewports. It contains icons for additional commands related to the active toolbar above. The sidebar is contextual and may change depending on which toolbar is selected. For example, it changes when we click on the Curve Tools toolbar, making commands related to curve drawing available. Here, we drag the sidebar out before docking it to the side again to demonstrate that the Rhino workspace can be customised.
Rhino Objects
Creating geometry
Let’s add a simple object to the document. Press the point icon on the sidebar and click in one of the viewports to create a point. A Layers panel is visible at the bottom right of the workspace. Currently, a layer named ‘Default’ is active and the point is stored in this layer; its display colour (black) matches the layer’s. Activate ‘Layer 02’ by checking the ‘Current’ column and rename it “Point 2”. Now we create another Point object using the command method. Type Point and when prompted, key in 0,0,10 to specify x, y and z coordinates. Notice that the point is visualised with a red outline, which corresponds to the active layer’s colour. Layers allow you to organize information/objects in the document, which is crucial as the the model gets more complex.
So far, we have created the simplest Rhino object – a point and learnt that we can do so via the drop-down menu, icon-based toolbars and command line interface. However, Rhino offers users a far more extensive vocabulary of geometric primitives for us to work with. We will introduce more of these geometry types over the next 6 weeks.
Selecting geometry
Previously, we learnt to use the right mouse button to rotate, zoom and pan in the viewport. On the other hand, the left mouse button is associated with selection. Left-click on an object directly to select it. Alternatively, you can left-click and drag the mouse to select an item with an enclosing/crossing window.
Holding onto shift allows you to add items to a selection.
While pressing ctrl allows you to remove it.
The Properties panel above Layers displays properties for selected object(s). The properties displayed depend on the type of object selected. Once we select the red point, the Properties panel updates, scrolling down we can view more detailed information such as the point’s coordinates. By default, if no object is selected, the active viewport properties are displayed.
Modelling Aids
Snaps
Rhinoceros provides modelling aids to help us create and edit geometry precisely. Let’s illustrate their use through another example. Draw some lines and/or polylines using the line or polyline commands. A polyline is a series of line segments that are joined together. Note that holding on to shift constrains your lines so they are orthogonal. You can repeat commands by simply hitting enter.
Now, we want to draw a curve (use the sidebar icon or command curve ; choose degree 3) and ensure that its control points precisely coincides with the vertices (points) of our drawn polyline. We may consider each control point as exerting an influence over a portion of the curve we are drawing. You will notice that the mouse marker jumps automatically to those points. This constraint is known as an object snap. You can specify which object snaps are active using the checkboxes at the bottom of the document e.g. Point, Mid, Cen etc. Each one affects how the marker is constrained differently.
Besides object snaps, we can also turn on/off global Grid Snaps, Ortho Snaps and Planar modelling aids. Practise drawing different lines and curves while using these aids. You may try the command InterpCrv to draw a curve that goes through the vertices of the polyline.
Gumballs
The gumball is a widget that allows us to move, rotate and scale an object. These operations are known as transformations. The gumball can be toggled on and off at the bottom right of the workspace. Click and drag the green arrow to translate /move the line in the y axis direction. Note that we can also click on one of the line’s vertices and transform it individually. Hide the default layer so we can isolate the curves. Select one of the control points of the interpolated curve. Let’s move this point more precisely in the y direction by keying in -5 after clicking on the green arrow. If you make a mistake, ctrl + z will undo the previous command. Rather than use the gumball, you can perform transformations through the command line or toolbar as well. Other transformations besides scaling, rotation and translation are also available though these remain the most commonly used operations.
Practice
Try creating other types of 2D curves e.g. circles through the toolbar or command line interface.
Experiment with the object snap settings . For example, try drawing a line that meets the interpolated curve at a perpendicular angle.
Conclusion
In this tutorial we learned the basics of the Rhino modelling environment and how to create simple geometric objects by using built-in commands and the mouse interface. This session does not aim to provide an exhaustive overview of Rhino’s feature, nor is it meant to be a CAD training session.
In the upcoming sessions, we will move beyond this direct modelling paradigm and some of the limitations it imposes, and learn to start generating geometry through programming instead. In fact, we will use Rhino primarily as an environment to visualise the geometric outputs of visual programs that we develop.
References
As mentioned earlier, this is not meant to be a CAD training course and hence we will only use a subset of Rhinoceros’ extensive suite of functionalities. Nonetheless, these functionalities are well documented and you may learn more about specific commands/operations through the help menu (F1). Alternatively there is an official Rhino online forum with an active community often posing questions and answers for various topics. We recommend you bookmark this page.
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