## Constructing a Sphere Feature

Construct Sphere dialog box

There are several ways to construct a sphere using PC-DMIS. The following table lists the various types of constructed spheres, along with their necessary inputs. Some features may require no inputs while others may require five inputs or more. The term 'Any' 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 Sphere | BF | At least 5 inputs are needed. | - | - | Constructs best fit sphere using given inputs
Best Fit with Recomp Sphere | BFRE | At least 5 inputs are needed. (1 must be a point) | - | - | Constructs best fit sphere using given inputs
Cast Sphere | CAST | 1 | Any | - | Constructs sphere at centroid of input feature
Project Sphere | PROJ | 1 or 2 | Any | Plane | 1 input feature will project sphere to work plane
Reverse Sphere | REV | 1 | Sphere | - | Constructs sphere 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 a sphere:

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

2. Input the desired features.

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

- Auto Sphere

- Best Fit or Best Fit Recompensate Sphere

- Projected Sphere

- Cast Sphere

- Reversed direction Sphere

4. Click the Create button.

The Edit window command line for a sample Sphere Construction would read:
feature_name=FEAT/SPHERE,TOG1,TOG4
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

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

AUTO is the default method of construction. This option automatically determines the best way to construct a sphere using the input feature(s). See "Auto Sphere Construction". | TOG1= POLR or RECT TOG2 = SPHERE TOG3 = BF / BFRE / CAST / PROJ / REV TOG4 = IN / OUT The first three lines displayed in the Edit window will be the same for constructed spheres. The fourth line will be slightly different, according to the type of feature being constructed. You can switch between the different types of spheres 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 paragraphs describe the available options for constructing a sphere.

More:

In / Out Sphere

Auto Sphere Construction

Constructing a Best Fit or Best Fit Recompensate

Constructing a Projected Sphere

Constructing a Cast Sphere

Changing the Direction of a Sphere