Constructing a Circle Feature

Construct Circle dialog box

There are several ways to use PC-DMIS to construct a circle. 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:	FEAT #3:	COMMENTS
Auto Circle	-	-	-	-	-	See "Auto Circle Construction".
Best Fit Circle	BF	At least 3 inputs are needed.	-	-	-	Constructs a best fit circle using the given inputs. See the Note below for recommended inputs.
Best Fit with Recompensate Circle	BFRE	At least 3 inputs are needed. (1 must be a point)	-	-	-	Constructs a best fit circle using the given inputs. See the Note below for recommended inputs.
Intersect Circle	INTOF	2	Circle, Sphere, Cone, or Cylinder	Plane	-	Constructs a circle at the intersection of a circular feature with a plane, cone, or cylinder.
			Plane	Circle, Sphere, Cone, or Cylinder
			Cone	Cone or Cylinder
			Cylinder	Cone
Cast Circle	CAST	1	Any	-	-	Constructs a circle at the centroid of the input feature.
Project Circle	PROJ	1 or 2	Any	Plane	-	One input feature will project the circle to the workplane.
Reverse Circle	REV	1	Circle	-	-	Constructs a circle with a reversed vector.
Tangent 2 Lines	TANLINES	2	Line	Line	-	Constructs a circle tangent to the two lines at a given diameter.
Tangent 3 Lines	TANLINES	3	Line	Line	Line	Constructs a circle tangent to the three lines.
Tangent 3 Circles	TANCIRCLES	3	Circle	Circle	Circle	Constructs a circle tangent to the three circles.
Scan Segment Circle	SCAN_SEGMENT	1	Scan	-	-	Constructs an arc from a part of a Linear Open or Linear Close scan.
Scan Minimum	SCAN_MINIMUM	1	Scan Minimum	-	-	Constructs a 2D circle of a given radius at a minimum point along a linear scan.
Cone Circle - also known as Gage Diameter	CONE	1	Cone	-	-	Constructs a circle at the specified diameter or height of the cone.
Sphere Circle	SPHERE	1	Sphere	-	-	Constructs a circle at the specified diameter or height of the sphere.
Cylinder Circle	CYLINDER	1	Cylinder	-	-	Constructs a circle at the specified diameter or height of the cylinder.

For Best Fit (BF) or Best Fit Recompensate (BFRE) constructions, while you can use any feature type for your input features, BF and BFRE fit types are typically used with point features or point sets (a scan of points, a feature set with points, or an expression that resolves to an array of points).

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:

Open the Construct Circle dialog box (Insert | Feature | Constructed | Circle).
Input the desired features.
Select the In or Out option.
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
Tangent 2 Lines
Tangent 3 Lines
Tangent 3 Circles
Scan Segment
Scan Minimum Point
Circle from a Cone
Circle from Sphere
Circle from Cylinder

Auto is the default method of construction. See "Auto Circle Construction".

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

The actual Edit report displays in all capital letters.

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" chapter.)

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 describe the available options for constructing a circle:

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

Constructing a Circle from a Sphere

Constructing a Circle from a Cylinder