Isometric Drawings from Digital Models
|This workflow shows how to use the Shear command to create an isometric view in Rhino of an existing digital model. The linework will then be exported to Illustrator where a few pointers on stylistic effects can help create descriptive and eloquent presentation diagrams.|
|Uses Tool(s)||Rhinoceros , Illustrator CS5|
Rhino is a great tool for quickly creating three dimensional drawings from an properly created digital model. The 3D viewport allows you to easily view the model in both perspective as well as parallel projection .
It is important to note that the parallel view is not a true 3D display mode, in that it is not geometrically correct for when creating axonometric drawings. Because of the relative ease of 3d modeling programs, it has become more acceptable to use these views (we do all the time, don't we?) as well as perspective views when showing the intricases of a 3d model. Below is an example of the linework from a simple parallel view versus a sheared model. Only the linework on the right contains linework that is projected and therefor keeps the proper dimensions:
This workflow shows how to use the shear command to create a correct isometric projection using an existing digital model and how to attribute proper lineweights to create a exquisite axonometric drawing!
It's best to Export the digital model or SaveAs so that you do not lose any information that you might need for creating other drawings as this workflow will edit the original geometry of the digital model.
Before transforming the model into an isometric form, it is important to clean up the model as much as possible. Helpful tools include:
- Selects all the curves in the model. Either delete these are put them on a separate later that you can delete.
- For any places or surfaces that are touching within view, you may want to create curves that references the intersection.
- It's much easier to work with a model that is close to the origin (0,0,0).
- Make sure you're in 4-view mode and use Zoom All Extents to see the entire model in all viewports.
In the Top viewport , select all (Ctrl + A) and use Rotate to rotate the entire model to the Axo angle desired (often this will be 30 degrees). If the model is near the origin, use the origin (0,0,0) for the point of rotation.
With the model still selected, type in the command Shear .
To establish the baseline for the shear, you need to indicate two points in the Right view-port. You may want the baseline to be vertical, so these two points need to be vertical to each other. The easiest way to do this is select the origin (0,0,0) for the first point and with Ortho on, select any point above it as the second. Alternatively, the first point can be the lower left corner of the model (see in the right view port) and a second point above that (again, with Ortho on).
At the prompt for Shear Angle, type -45 and press Enter. The model will shear over 45 degrees to the right.
In the Top viewport, you should now see you model in pseudo-axonometric. From the Top, all measurements will be geometrically correct (1:1). Note that measuring the model, all vertical measurements are going to be 1.41 times larger than they should be, due to the stretch applied with Shear.
Using Macros to Automate Shear
All of the above commands (view, rotate, shear) can be automated by the following macro. Use the MacroEditor command and paste in the sentence below and click the Run button. Select the objects you would like to shear and ta-da!
(For Rhino running in English):
! _Select _Pause _SetActiveViewport Top _Rotate 0 30 _SetActiveViewport Right _Shear w0 w0,0,1 -45 _SetActiveViewport Top
Staying in the Top viewport, you can now use the Make2d Command to turn the object into linework.
Note: Make2d will take a long time to process for elaborate digital models. If your model is complex, your computer is slow and/or you do not have a lot of memory, it is not likely to succeed - it may take a long time or crash Rhino. Bad objects or many objects with concurrent edges will also cause Make2d to take much longer to execute.
Drawing Cleanup and Lineweight Lesson
An axonometric drawing reads spatially pretty easily by the nature of a parallelogram as a rectangle in space. However, it's quick to look over and miss some of the mistakes the make2d command does to the linework. Be sure to check for clean corners, duplicated lines, overly complicated linework (especially if you're going to show the hidden lines) or missing intersections.
Lineweight is essential to the clear and correct reading of your drawing. Clean up the drawing and reorganize the different curves into layers that correspond to the proper lineweights for an axonometric . The most difficult reorganization will likely occur for the first group (edges).
The above drawing consists of four new layers: Edge, Profile, Corner, Detail.
Export to Illustrator
Once all the layers are organized, select all the linework and export it to Illustrator . Because this drawing was created in the Top view using the Shear command, there is a sense of scale that references the plan and section drawings. Therefore, you should export at a specific scale.
In Illustrator , change the linework according to the different layers created. The thicker edge lines should not be too dark that they overwhelm the drawing. Hidden lines should be dashed.
Adding Color, Renders, and Shadows
Axonometric drawings can emphasize different things, such as circulation, materiality, connections or general interior conditions. Tonal values or effects in Illustrator can help illustrate these different diagrammatic ideas.
- Using simple Rhino Render, use bright colors to reference different materials or conditions (structure vs. envelope). Change the transparency to 50% to help the drawing read as ghosted. Place this rendered image behind the linework created above.
- Emphasize Vertical surfaces from Horizontal Surfaces by making the color slightly different from each other (darker tone)
- Emphasize the interior elements by creating a transparent outer envelope and opaque interior elements.
- Add a directional line to create shadows within the drawing. Increase the contrast of these shadows in Photoshop to offer more control of the depth / contrast ratio. Add a base plane to provide for ground shadows as well.
- Difficulties getting the Shear command to work properly?
- As you click through the command, make sure you are not clicking on the object - but in the background area of the viewport. This makes sure that the all the points you click on are on the control plane, and therefor easier to make a vertical line as the baseline for the Shear command.