## Constructing an Ellipse Feature

Construct Ellipse dialog box

There are several ways to construct an ellipse using PC-DMIS. The following table lists the various types of constructed ellipses, along with their necessary inputs. Some features may require no inputs while others may require three inputs or more. The term 'Any' in the following table indicates that the construction can take any type of feature as input for construction. PC-DMIS allows the features to be selected in any order.

CONSTRUCT FEATURE TYPE | SYMBOL IN EDIT WINDOW | # OF INPUT FEATS | FEAT #1: | FEAT #2: | COMMENTS
Best fit Ellipse | BF | At least 4 inputs are needed or a scan or set with 4 points. | - | - | Constructs best fit ellipse using given inputs
Best fit with Recompensate Ellipse | BFRE | At least 4 inputs--with one input being a point--are needed or a scan or set comprised of at least 4 points. | - | - | Constructs best fit ellipse using given inputs
Intersection | INT | 2 | Cylinder | Plane | Constructs an ellipse at the intersection of the input features
Cast Ellipse | CAST | 1 | Any | - | Constructs ellipse at centroid of input feature
Project Ellipse | PROJ | 1 or 2 | Any | Plane | 1 input feature will project ellipse to work plane
Reverse Ellipse | REV | 1 | Ellipse | - | Constructs ellipse with a reversed vector

Note: If you select inappropriate feature types, PC-DMIS displays "Cannot construct [feature]. Combination of input features not accepted." on the status bar.

To construct an ellipse:

1. Access the Construct Ellipse dialog box (Insert | Feature | Constructed | Ellipse).

2. Input the desired features.

3. Select the In or Out option.

4. Select the method of construction. Available options include:

- Auto Circle

- Best Fit or Best Fit Recompensate Ellipse

- Cast Ellipse

- Projection Ellipse

- Reverse direction Ellipse

5. Some ellipse types have additional options or items that appear in the dialog box when selected. Select or use these options as needed.

6. Click the Create button.

The Edit window command line for a sample Ellipse Construction would read:
feature_name=FEAT/Ellipse,TOG1,TOG4
THEO/x_cord,y_cord,z_cord,i_vec,j_vec,k_vec,major diam,minor diam,i angle vec, j angle vec, k angle vec
ACTL/x_cord,y_cord,z_cord,i_vec,j_vec,k_vec,major diam,minor diam,i angle vec,j angle vec,k angle vec
CONSTR/TOG2,TOG3,TOG5,feat_1,feat_2, …

Note: The actual Edit report will be displayed in all CAPS.

Auto is the default method of construction. See "Auto Circle Construction". | TOG1= POLR or RECT TOG2 = ELLIPSE TOG3 = BF / BFRE / CAST / INT / PROJ / REV TOG4 = IN / OUT TOG5 = 2D / 3D (This appears only if TOG3 reads BF or BFRE)

The first three lines displayed in the Edit window will be the same for constructed ellipses. The fourth line will be slightly different, according to the type of feature being constructed. You can switch between the different types of ellipses by placing the cursor on TOG3 and pressing F7 and F8. (See "Command Mode Keyboard Functions" in the "Using the Edit Window" section.)

When two or more features are involved, PC-DMIS automatically determines the necessary order of the input features. This improves the accuracy of the measurement process.

The following paragraphs describe the available options for constructing an ellipse:

More:

In / Out Ellipses

2D / 3D Ellipse

Constructing a Best Fit or Best Fit Recompensate Ellipse

Constructing an Intersect Ellipse

Constructing a Cast Ellipse

Constructing a Projected Ellipse

Changing the Direction of an Ellipse

Auto Ellipse Construction