Draft the side surface

1. Create a new layer and name it “Main SRF”. The new layer should retain the layer focus.
2. Create a draft surface using the theoretical line in the Z-direction. Leave the option box open.
3. Move to the side view.
4. Increase the length of the draft surface such that the surface covers all of the scan lines.

   

5. Select the new draft surface and turn on the Cv/Hull display.
6. Pick the CVs highlighted in the image above.
7. Choose the Move tool from the marking menu.
8. Press (Windows) or (Mac) (this will activate Magnetic Snap).

   

9. Use the to click near to the unselected CV on the right-hand side.
   TipUsing the right mouse button will restrict movement to the Z-direction and will allow the selected CV to move onto the desired CV.

   

Having produced a surface in the Z-direction, the number of degrees will need to be increased to shape the surface in the Y-direction.

To increase the degree

1. In the Control Panel, increase the Degree value from 1 to 2.
2. Tumble the view to a 3D impression.
3. Turn on the X Cross Sections.
4. Make sure the Step size value is set to 10.
5. Choose the marked hulls and move them in the Y-direction. Use the Control Panel > Evaluate > Move CV tool to lock the X and Z directions (use HULL and XYZ).

   

6. Fit the side surface to the scan lines by moving the hulls.

   

In the above image, the marked area denotes the area where the surface will fit to the scan lines. The marked area can be determined by examining the previously fitted curves. The overall surface must have a good CV distribution. As for the marked area, the surface must fit to the scan lines. It is a possibility that three hulls are not enough, in which case, the degree should be increased to 3. Also, at this stage in the development of the model, avoid moving single CVs as the surface could be damaged. Upon reaching the point where the model cannot be improved, switch the type of surface to gain more flexibility. But first, copy the edges of your current surface to create a square.

To change the type of surface

1. Double-click the Curve Edit > Create > Duplicate Curve tool to produce the option box.
2. Set the options as follows:

   Set this parameter...	To this value
   Duplicate type	No rebuild
   Smoothing	off
   Interactive	off
   MinMax display	off
   Auto Recalc	on

3. Select the edges highlighted in the image below.
4. Press the Go button.

   

5. Delete the surface.
6. Align the small curves onto the bigger ones using the Align tool.
7. Set the Align Control options as shown in the image below.

   

To create a square surface

1. To build a surface from the four curves, double-click the Surfaces > Boundary Surfaces > Square tool.
2. Set the Advanced tab options as follows:

   Set this parameter...	To this value
   rebuildCurves	set all to FIXED Continuity, no Rebuild
   Blend Type	LINEAR
   1-3 Boundary Blend	0.500
   2-4 Boundary Blend	0.500
   Explicit Control	on
   U/V Sync Degree	off
   U degree	3
   V degree	5
   U spans	1
   V spans	1
   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. Pick the four curves in a clockwise direction.
4. In the Control Panel, turn on the X cross sections.

   

5. In order to see just the CVs that belong to the curves, turn off the Cv/Hull display for the square.
6. For the best fit between the square and the scan lines, move the CVs of the curves (mainly in the Y-direction).
   TipWhile moving the CVs remember to maintain an even distribution of CVs across the curves. Use the Locator tools to monitor the curvature of the curves – try to avoid inflections in the curvature.

   

After the recent modifications to the model, the theoretical line may need to be adjusted. If adjustments to the theoretical model are required, use the Curve Edit > Curve Planarize .

As for the square surface, the primary requirement is that it fit to the marked area of the scan lines.

To duplicate the square

1. Double-click the Edit > Duplicate > Mirror tool to produce the mirror options box.
2. Set the mirror options as follows:

   Set this parameter...	To this value
   Mirror Type	Duplicate
   Mirror Across	XZ

3. Press the Go button.

   

The model now has two side surfaces, but they are not identical. The original side surface has a construction history while the mirrored surface does not. To correct this imbalance, delete the curves used to build the original square – the curves hold the construction history. When the side surfaces are identical (without history), they are complete for this section of the tutorial.

After deleting the curves, the only possibility to model both side surfaces is to use the direct modeling method. You will use the same techniques that were applied to the model when you used curves to modify the square surface. Remember, when applied to two symmetrical surfaces, the direct modeling method requires that corresponding CVs will have to be selected, movement in the X and Z directions must be driven from the Control Panel > Evaluate > Move CV tool, and movement in the Y-direction must be conducted using the non-proportional scale. In repeating techniques, you not only gain more experience but may also find new methods to complete the task.

Having completed the two side surfaces, the next step will be to complete the top surface.