How to make parallel projection in Rhino?

To make parallel projection in Rhino, you typically adjust the settings for a specific viewport using the Properties panel. This allows you to change how objects are displayed in that particular view.

Here's a straightforward method based on using the Viewport Properties:

Adjusting Viewport Projection

Rhino viewports can display your model in various projection modes, including perspective and different types of parallel projection. Changing a viewport to parallel projection involves accessing its specific settings.

The referenced method provides a clear example of how to set a viewport to parallel projection:

1. Maximize the Desired Viewport: Double-click on the title of the viewport you want to change (e.g., Top viewport) to make it fill the Rhino window.
2. Deselect Objects: Press the Esc key to ensure no objects are currently selected in your model. This prevents the Properties panel from showing object properties instead of viewport properties.
3. Open Properties Panel: Type the command Properties in the Rhino command line and press Enter. This will open the Properties panel, usually located on the right side of the interface.
4. Access Viewport Settings: With no objects selected, the Properties panel will display the settings for the active viewport (the one you just maximized).
5. Set the Projection: In the Properties panel, locate the section for Viewport Properties. Find the Projection setting and change it. According to the reference, you can set the Projection of the Top viewport to Parallel Reflective.

You can choose other parallel projection types from the dropdown list if available in your Rhino version, such as:

• Parallel
• Isometric (various angles like Northeast, Northwest, Southeast, Southwest)
• Dimetric
• Trimetic

Most standard orthographic viewports like Top, Front, Right, and Back are set to Parallel projection by default. You might use this method to change a view that was previously set to perspective, or to set up a specific isometric view.

Understanding Parallel Projection

In parallel projection, all projection lines from the object to the view plane are parallel. This means objects do not appear smaller as they get farther away, preserving scale and allowing for accurate measurement directly from the viewport. This is in contrast to perspective projection, which simulates how we see in the real world, with objects appearing smaller in the distance.

Key Characteristics of Parallel Projection:

• True Scale: Measurements in parallel views correspond directly to the model's actual dimensions along the view plane axes.
• No Foreshortening: Parallel lines in the model remain parallel in the view (unlike perspective, where they converge).
• Ideal for Technical Drawing: Often used for plan views, elevations, and sections in architecture, engineering, and product design.

Changing a viewport's projection is a fundamental step for creating technical documentation or specific visual representations of your 3D model.

Step	Action	Result
1. Maximize Viewport	Double-click Viewport Title	Viewport fills screen
2. Deselect	Press Esc	Ensures Viewport Properties show
3. Open Properties	Type Properties command	Properties panel opens
4. Set Projection (Ref.)	Choose Parallel Reflective	Viewport displays in parallel projection

This process gives you control over how each part of your model is viewed and documented.