Rhino L1 08: Offsets and Fillets

Summary

In this part 2 of our 2 part NURBS series, we’ll be finishing up the ceramic vase by creating interior wall offsets, surface fillets, joining up the ends with a blend surface, and creating a surprisingly simple handle.

Full Video Transcript:

…{continued from previous video}

When you’re done, use Surface palette > Rectangular Plane, corner to corner. Click to define a bottom for the vase. If the pink side of the surface is facing down, select it, and type ‘flip’ to flip the surface normal so that it’s facing the outside of the vase.

Before we trim these, I want to create the inside surfaces for the vase, to give it some thickness. Run Surface Tools > Offset Surface on the second row. Select both surfaces, and hit [enter]. The arrows show us which direct Rhino is going to offset the surfaces. Click ‘FlipAll’ in the command line so that they’re pointing inward, and type ’2mm’ to define the offset distance, or thickness of our vase. Hit ‘enter.’

Select the newly offset surfaces and type ‘flip’ so that they’re facing the inside of the vase, and take a look inside. Notice that Rhino has had to add much more complexity to the interior offset surface in order to keep the offset within tolerance. This offset is EXACTLY 2mm from the outside surface at all points, plus or minus a tolerance value. This is the technically "correct" offset, but it’s also a heavier surface, and not as "clean" of a "Class-A" surface.

Delete the interior surfaces, select the exterior ones, and run the Offset Surface tool again. Flip the direction, and this time check the "loose" parameter in the command line, and hit [enter]. Flip the interior surfaces, and notice that this time the offset has happened without all those extra spans on the inside. Rhino has offset each span of the outside surface exactly 2mm. The wall thickness may vary slightly across the height of the vase, but the resulting surface geometry is much smoother, much cleaner. In your work, you can use whichever type of offset you prefer.

Select the interior surfaces and hit the lightbulb icon at the top of the window to temporarily hide them.

Selec the ‘trim’ tool. The trim tool works with surfaces exactly the same way that it works with curves. Select both of the objects you want to cut, hit enter, then click the parts you want to cut off.

When we’re done, the surfaces match perfectly, but we can see that they’re not watertight yet: the naked edge is still showing. Use the Join tool, click the objects to join, and hit [enter]. The result should be a nicely closed manifold surface.

Select Solid Tools > Variable Radius Fillet. Drag to box-select the edges to fillet, and hit enter. To change the radius of the fillet, either click and drag the center of the fillet preview to dynamically resize it, or click "Set All," and type 4mm. Hit [enter] to commit the fillet.

To hide this surface and bring back the interior surfaces, click and hold on the lightbulb icon, and select "swap hidden and visible objects."

Lets use a different method to fillet these surfaces; one that shortcuts all that trimming, and does it all for us in one step. Select the surface fillet tool from the main toolbar, and type 2mm [enter] to define the fillet radius. Then click the surface on the side that you want the fillet to appear. If I click the OUTSIDE of the bottom surface, it will try to fillet outward, so I need to be aware of what I click. Click the inside of the vase, and the inside of the base. Viola! Fillet!

Select all three objects and click the ‘join’ tool. Notice that the surface normals have automatically aligned themselves to one another. Right-click the lightbulb icon to bring back the exterior surfaces.

To close off the vase, hit the Surface Tools > Blend Surface tool. Select the outer edge of the vase, followed by the inner edge, and hit [enter]. Click the "Preview" check box in the "Adjust Blend Bulge" window to see the result, and drag the tension sliders to adjust the tension of the blend on either side. When you’re done, hit OK.

Select all of the surface of the vase, and hit ‘join’.

One more thing before it’s playtime: head to the right view and use the control point spline to draw the profile of a handle.

Then run Solid Tools > Pipe, Round Caps. Select the curve, then type 2mm, hit [enter], [enter], and [enter] a third time.

Move to the Top view, select the pipe object, and run Scale > Scale 1D. Click in the center of the handle, click toward the outside edge, and then click to define a new width.

Move back to Perspective, and we’re done!

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about adam: Adam O'Hern is an industrial design consultant specializing in visual brand languages, and has designed products ranging from laptops to power tools, classroom toys to bathroom fixtures, and robots to lint rollers. He has published with 3DWorld Magazine, CGTuts+, and Luxology, and works with Josh Mings of SolidSmack.com on EngineerVsDesigner.com.