To connect the rear of the top curve to the side surfaces of the model

1. Using the Viewing Panel, move into the side view.
   NoteThe ViewCube viewing control displays by default, but you will use the View Panel in these tutorials. If you have not done so already, switch view controls, by selecting Preferences > General Preferences ❒, clicking Viewing, and then selecting View Panel. For information on the ViewCube, see Use the ViewCube tool and NavBar.
2. Make sure that the Perspective mode in the Viewing Panel does not contain a check mark.
3. Starting at the rear point of the top curve of the center line, create a curve that runs in the Z-direction.

   

4. Select both side surfaces.
5. Make sure that you are still in the side view.
6. Using the Surface Edit > Create CurvesOnSurface > Project tool, project the created curve onto the selected surfaces.

The Surface Edit > Create CurvesOnSurface > Project tool always projects the curve onto the selected surfaces in the direction of the current view. Working in the orthographic window while using the Surface Edit > Create CurvesOnSurface > Project tool requires some special considerations.

Using the Project tool in the orthographic window

• When executing an operation that requires a direction, make sure that the Perspective option in the Viewing Panel is not check marked.

  

• Before projecting a curve, make sure that you are in a main view (the side, top, or front). To ensure that you are in the appropriate view, choose the corresponding arrow in the Viewing Panel. Do not rely on the black colored arrows in the Viewing Panel, as they do not show that you are still in the marked view. To be safe, choose the appropriate arrow before projecting.

To build the foundations of the top surface

1. Create a degree 3 edit point curve between the surface corners as shown in the image below.
2. Create a degree 3 edit point curve between the two Curve on Surfaces as shown in the image below.

   

   Examine the top curve created in the “Fitting curves to X-scans” section. For the top portion of the curve, note that a degree 4 curve was used. To achieve the same results with the current curve, increase the Degree values for both of the newly created curves.

3. Select the first curve.
4. Turn on the Cv/Hull display.
5. In the Control Panel, increase the Degree value to 4.

   

6. Select the second curve and repeat Steps 4 and 5.
7. Align the completed curves by position to the corner points of the side surface and to the two Curve on Surfaces. In doing so, the construction history of the curves will be updated to ensure contact with the side surfaces at all times. The construction history option of the Align tool should be turned on.

Reshape both curves by employing the same methods used to fit curves to the X-scans.

Basic rules for modeling the CVs of curves across the Y0 plane

• Select the CVs you need to model, as well as their corresponding CVs.
• Center the pivot point and use the non-proportional scale when modeling across the Y0 plane.
• If modeling in the X and Z directions, use the Control Panel > Evaluate > Move CV tool.

To create a square surface

1. Double-click the Surfaces > Boundary Surfaces > Square tool to produce the options box.
2. Set the options as follows:

   Set this parameter...	To this value
   Curves	set all to FIXED Continuity, no Rebuild
   Blend Type	LINEAR
   1-3 Boundary Blend	0.500
   2-4 Boundary Blend	0.500
   Explicit Control	off
   Max. New Spans	0
   Insert at Midpoint	off
   Colinear options for boundaries	Set all off
   Create History	on
   Auto. Recalc	on
   Boundary Labels	on
   Continuity Check	on

3. Construct a square surface using the two curves and both side surfaces.

   

The newly created surface should be flat and match the length of the top curve of the center line. The next step in the process will be to shape the top surface to fit the scan lines. Because the top surface has a square history, modify the curves on the front and rear of the surface. Once the square surface is updated, check the shape of the surface and compare the results to the scan lines by turning on the cross-sections in the X and Y directions.

To reshape a square surface

1. Turn off the CVs of the square surface.
2. Make sure the CVs of the curves are turned on.
3. Select the square surface and turn on the X-Cross-Sections and the Y-Cross–Sections.
4. Make sure that the Step size value is set to 10 in the cross-section portion of the Control Panel.
5. Make the scan lines of the X-scans layer and Y-scans layer are both set to Visible and Set state > Reference.
6. Modify the CVs of both curves to fit the square surface on the scan lines. (Move the CVs in the Z-direction, using the Control Panel > Evaluate > Move CV tool).

   

When fitting the top surface to the scan lines, it may not be clear as to where the surface has to deviate from the scan lines. To help define the area where the top surface has to fit the scan lines, use the X-curves created in the “Fitting curves to X-scans” section. Remember that the scan lines represent the finished model, including the fillets. At this point in the modeling process though, the theoretical model does not include fillets. Using the dimensions of the X-curves, you can determine the location of the fillets and where the top surface needs to fit the scan lines.

After obtaining an acceptable level of deviation to the scan lines, create the fillets to see if the surfaces are located in the right position. At this point in the modeling procedure, the fillets serve as an evaluation tool to help determine if the main surfaces are correct.

If the resulting fillets are not correct, the main surfaces and theoretical line can be further manipulated to achieve the desired results.

To create a fillet between two surfaces

1. Double-click the Surfaces > Surface Fillet tool to produce the option box.
2. Set the options as follows:

   Set this parameter...	To this value
   Construction Type	CONSTANT
   Section Type	CURVATURE
   Span Placement	DEFAULT
   Curvature	BOTH SIDES
   Radius	18
   Extend	off
   Explicit Control	on
   U Degree	6
   Max. Spans	10
   Trip Type	CURVES ON SURFACE
   Auto Recalc.	off
   Continuity check	on
   Curvature Comb	off

3. Select the top surface.
4. A blue arrow points in the direction of the current normal of the surface. Click the arrow to make sure it is pointing inwards.
5. Press the Accept button at the bottom of the screen.
6. Select the original side surface and repeat Steps 4 and 5.

   

7. Choose Pick > Nothing .
8. Select the fillet surface.
9. Turn on the X-Cross-Sections to compare the fillet surface with the X-scan lines.

If the main surfaces have an acceptable fit to the scan lines, the fillet surfaces should also fit to the scan lines. If the radius is unknown, experiment with the Radius option value. The objective is to find a solution that allows the fillet entry lines to obtain a close proximity to the endpoints of the blend curve that represents the connection between the top and side of the X-scan line.

In the image above, the area has been marked where the fillet surface does not have an acceptable proximity to the scan lines. To correct the fillet surface, begin by examining both the top and the side surfaces. If either of the surfaces is found to be in error, corrections will have to be conducted. To reduce confusion in the view and speed-up the modification process, make the fillet surfaces invisible.

Factors to consider when making corrections to surfaces

• When modifying a side surface, remember that there are two side surfaces. To maintain the symmetrical character of both side surfaces, corresponding CVs must be selected for movement and modification.
• When modifying the top surface, keep in mind that the top surface runs across the Y0 plane, and as a result, there are special modification requirements for the movement and modification of CVs.
• It is important to remember to maintain the planar character of the theoretical line. The safest course of action is to move the hulls (not single CVs) that represent the theoretical line.

To change the theoretical line by moving hulls

1. Select the fillet surface.
2. Choose ObjectDisplay > Invisible from the menu.
3. Turn on the CVs of both side surfaces.
4. Select the upper hull of both surfaces.
5. Choose the Transform > Local > Center Pivot tool.
6. Move both hulls using the non-proportional scale.
7. Choose Pick > Nothing .
8. Select both hulls again.
9. Choose the Control Panel > Evaluate > Move CV tool and slide both hulls in a downward direction. This procedure should require only a small degree of movement.
10. Choose ObjectDisplay > Visible from the menu to make the fillet visible again.

    

To save your work

1. Create a new layer and name it “my main srf”.
2. Select the newly created side surfaces, the top surface, and the fillet surface.
3. Assign the selected surfaces to the “my main srf” layer.
4. Save your work.

To construct a new construction history using the Align tool

If the construction history of the top surface is lost, the connection to the side surfaces will also be lost. To rebuild the construction history of the top surface, a new modeling strategy will be introduced to achieve the desired results. You can also use this strategy if you lose the symmetrical character of the side surfaces.

• Delete the mirrored surface to make sure you have just the original side surface.

  

• Mirror the side surface to ensure that both side surfaces are identical.

  

• In the Alignment Type Option tab found in the Align Control box, set the Partial Joins option to Tjoin. Align the top surface by position to the first side surface. Repeat the procedure on the other side.

  

  NoteIf the planar characteristics of the theoretical line have been lost due to the accidental movement of a single CV, use the Curve Edit > Curve Planarize tool to re-establish the characteristics. The Curve Edit > Curve Planarize tool can be employed on curves as well as surface edges, such as the theoretical line. When using the Curve Edit > Curve Planarize tool, set the Default Projection Plane to Best, and turn off the Keep Originals option. Repeat the planarize process for the other side surface.

If all of the procedures of this section were successfully executed, your model should resemble the image below.