## Constructing a Circle Feature

Construct Circle dialog box

There are several ways to construct a circle using PC-DMIS. The following table lists the various types of constructed circles, 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 Circle | BF | At least 3 inputs are needed. | - | - |  | Constructs best fit circle using given inputs
Best fit with Recompensate Circle | BFRE | At least 3 inputs are needed. (1 must be a point) | - | - |  | Constructs best fit circle using given inputs
Cast Circle | CAST | 1 | Any | - |  | Constructs circle at centroid of input feature
Cone Circle (also known as Gage Diameter ) | CONE | 1 | Cone | - |  | Constructs circle at the specified diameter or height of the cone
Intersect Circle | INTOF | 2 | Circle, Sphere, Cone, or Cylinder | Plane |  | Constructs circle at the intersection of a circular feat with a plane, cone, or cylinder
Plane | Circle, Sphere, Cone, or Cylinder
Cone | Cone or Cylinder
Cylinder | Cone
Project Circle | PROJ | 1 or 2 | Any | Plane |  | 1 input feature will project circle to work plane
Reverse Circle | REV | 1 | Circle | - |  | Constructs circle with a reversed vector
Tangent 2 Lines | TANLINES | 2 | Line | Line | - | Constructs circle tangent to the two lines at a given diameter.
Tangent 3 Lines | TANLINES | 3 | Line | Line | Line | Constructs circle tangent to the three lines.
Tangent 3 Circles | TANCIRCLES | 3 | Circle | Circle | Circle | Constructs circle tangent to the three circles.
Scan Segment Circle | SCAN_SEGMENT | 1 | Scan | - |  | Constructs arc from a part of a Linear Open or Linear Close scan.

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 a circle:

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

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 Circle

- Intersect Circle

- Cast Circle

- Projected Circle

- Reverse direction Circle

- Scan Segment

- Tangent 2 Lines

- Tangent 3 Lines

- Tangent 3 Circles

- Circle from a Cone

5. Some circle 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 Circle Construction would read:
feature_name=FEAT/CIRCLE,TOG1,TOG4,TOG5
THEO/x_cord,y_cord,z_cord,i_vec,j_vec,k_vec,diam
ACTL/x_cord,y_cord,z_cord,i_vec,j_vec,k_vec,diam
CONSTR/TOG2,TOG3

If TOG2 = CIRCLE and TOG3 = BF or BFRE then the command has the following format:
feature_name=FEAT/CIRCLE,TOG1,TOG4,TOG5
THEO/x_cord,y_cord,z_cord,i_vec,j_vec,k_vec,diam
ACTL/x_cord,y_cord,z_cord,i_vec,j_vec,k_vec,diam
CONSTR/CIRCLE,TOG3,TOG7,feat_1,feat_2, …
OUTLIER_REMOVAL/TOG6, stdDevMultiplier
FILTER/TOG6, UPR =cutoffFrequency

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 = CIRCLE TOG3 = BF / BFRE / CAST / CONE / INTOF / PROJ / REV / TANLINES / TANCIRCLES / SCAN_SEGMENT TOG4 = IN / OUT TOG5 = LEAST_SQR / MAX_INSC / MIN_CIRCSC / MIN_SEP / FIXED_RAD (only for measured, BF and BFRE circles)

TOG6 = ON or OFF

TOG7 = 2D or 3D (This appears only if TOG3 reads BF or BFRE)

stdDevMultiplier = This multiplier value determines whether or not a measured point is an outlier. If the point from the circle is further than the standard deviation multiplied by this, then it is an outlier and will be removed if you have selected the Remove Outlier option.

cutoffWavelength = This value controls the amount of data smoothing. The longer the wavelength the more the smoothing.

The first three lines displayed in the Edit window will be the same for constructed circles. The fourth line will be slightly different, according to the type of feature being constructed. You can switch between the different types of circles by placing the cursor on TOG3 and pressing F7 or 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 a circle:

More:

In / Out Circle

2D / 3D Circle

Auto Circle Construction

Constructing a Best Fit or Best Fit Recompensate Circle

Constructing an Intersect Circle

Constructing a Cast Circle

Constructing a Projected Circle

Changing the Direction of a Circle

Constructing a Tangent Circle

Constructing an Arc from Part of a Scan

Constructing a Circle at a Scan's Minimum Point

Constructing a Circle from a Cone