SubD Base & Reference Surface

1. Hide references and create the base box

Hide the reference curves for now — they come back later. In the SubD tab create a box, typing 0 to place its starting point at the center.

2. Center the object in all views

Use Pan, Zoom and Rotate, then Zoom Extents All to center the object everywhere. With the object selected, Artisan Center in the command bar snaps it onto the axis.

3. Split the object into two halves

In Perspective, run Split with Edge Loop enabled in the command bar: select the object, double-click the center edge and press Enter.

4. Remove the lower half and shape the lower edge

Delete the lower half to hollow the element. With the Edge Filter on, double-click a lower edge to grab the loop, move it down 1 mm with the Gumball, and — without deselecting — use Insert Edge to add another loop.

5. Refine curvature with scaling and edge positioning

Scale the lower edges down with the Gumball (hold Shift for proportional scaling) until the curvature matches the reference, then fine-tune the new edges along the X axis to smooth the outer curve.

6. Duplicate edges to create a reference surface curve

In the Curve tab, use Duplicate Edge on the two center edges — switching the layer before pressing Enter drops the duplicates where you want them.

7. Blend and edit the reference curve

Blend the two duplicated edges into a smooth curve with Tangency continuity, then edit it from the Front view: the handles should lift the curve about two grid squares above the lower part of the object.

8. Trim the curve and prepare the bottom reference surface

Place a point at the center of the curve and Trim the right side with it (Sub Object Selection off so the full curve selects), then delete the point and duplicate the edge curves of the reference surface too.

9. Build the bottom reference surface with Rail Revolve

In the Surface tab, Rail Revolve builds the bottom reference: select the trimmed curve, then the edge, then click the center point of the surface and the cut point of the curve. Park the result on its own layer so it reads in another color.