Dimensioning a 3D model in AutoCAD typically involves aligning the User Coordinate System (UCS) to the specific face or plane you want to dimension, and then applying standard dimensioning tools.
One common method involves adjusting the UCS to match the orientation of the object face you are dimensioning. Here’s a breakdown of the process:
Steps to Dimension a 3D Model Face
To add dimensions directly onto the faces of a 3D solid or surface in AutoCAD, you can follow these steps:
- Go to Home Tab. Locate the Home tab on the AutoCAD ribbon interface.
- Hover your mouse over the Coordinates panel. This panel usually contains tools related to the UCS.
- Click on Origin UCS. This command allows you to place and orient the UCS using a specified origin point and direction.
- Place the UCS on the object face where the dimension needs to be added. Select a point on the desired face to set the origin of the new UCS. AutoCAD may then prompt you to define the X and Y axes to orient the UCS precisely on that face.
- Go to Annotate Tab. Switch to the Annotate tab on the ribbon, which contains all dimensioning and annotation tools.
- Click on Dimension. Select the standard Dimension tool. Since the UCS is now aligned with your face, dimensions added will be parallel to that face.
- Place the dimension where is needed. Use standard object snaps (like Endpoint, Midpoint, Intersection) to select the points you want to dimension on the face and place the dimension text.
Why Adjust the UCS?
In 3D space, dimensions are inherently placed on a 2D plane. By default, AutoCAD dimensions are placed on the XY plane of the current UCS. When dimensioning a 3D object, its faces are often not parallel to the World Coordinate System (WCS) XY plane. Adjusting the UCS to align with the face ensures that the dimensions you add are coplanar with that face and accurately represent the distances on that specific surface.
Practical Considerations
- Dimension Styles: Ensure you have a suitable dimension style set up before adding dimensions. This controls the appearance (text height, arrows, units, etc.).
- Dimension Types: You can use various dimension types like linear, aligned, angular, or radius dimensions, depending on what you need to measure on the face.
- Dimensioning in Layouts: Alternatively, many users create 2D views of their 3D model in a layout (using ViewBase, ViewProj, etc.) and add dimensions to these 2D projections, which can sometimes be easier for creating documentation drawings. However, the method described above allows dimensioning directly on the 3D model itself.
By setting the UCS on the face you intend to dimension, you tell AutoCAD the correct plane to work on for that specific annotation, making 3D dimensioning straightforward.
