Rhino L1 09: Revolve Surface

Summary:

• Using a simple revolve surface for multiple parts of a space blaster design.

Full Video Transcript:

Ladies and gentlepeople, today you are in for a treat! We’re going to be building a space blaster in Rhino using nice, clean NURBS surfaces, and it’s going to be fun. So pop open Rhino and lets get to work.

Our basic shape is going to begin its life as a revolve, but in order for this to work correctly it’s really important that we are very deliberate with our first few clicks. So pay attention!

Enable grid snap, and run the Control Point Curve. Click to define a basic shape similar to mine, and there are two things I want to make absolutely sure of before we go any further: 1) the start and end points should be right ON the X axis, which is why we used grid snap, and 2) the points adjacent to the start and end points should be directly above their respective endpoints on the Y, insuring that our curve is exactly perpendicular to the X axis at both ends.

Enable Control Points for the curve. To add a bit of detail, select a couple of points and type ‘Weight’ to activate the Weight tool. Drag the slider to adjust the influence of the selected control points, making the curve appear sharper. I don’t use weights often, but it’s nice to know they’re available.

Run the Revolve command, select the curve, and hit [enter]. To define the revolve axis, click the two end points of the curve, again using grid snap to insure that we’re revolving exactly around the X. In the command line, click to set ‘DeleteInput’ to ‘Yes.’ Type ‘zero’ [enter] to define a Start angle, and 180 [enter] to rotate half-way around. Our blaster is going to be symmetrical, so there’s no point in building both halves if we don’t have to! We’ll build half of the model, then mirror it across.

When you shade the viewport, the result should look really clean at both ends. Perfect.

Now we’ve done all the work of making this perfect shape for the barrel, why not re-use it for the handle? To quickly duplicate the shape, click and drag it a little bit, then hold the [alt] key to enter duplicate mode, then drag the mouse a bit more (you’ll see a ‘plus’ sign appear under the mouse). Then let go of the mouse button, and finally let go of the [alt] key.

Use the Rotate tool to rotate the handle around a bit, and nudge it into place.

To massage these shapes, enable control points. I want to angle the back side of the blaster a bit, so select the rear control points and use the Transform > Shear command. Click the point you want to stay put, click the point you want to move, then then click to define the desired angle.

Maximize the Right viewport.

Hide control points for the body, then show the control points on the handle. I’d like to flatten out the handle in profile, so select the top-most points across the entire handle, then run Transform > Set XYZ Coordinates (or type ‘SetPt’ in the command line), and by looking in the bottom-left corner of the viewport I know that we want to set all of these points so that they’re equal on the Z axis. Un-check the X and Y axiis in the Set Points dialog, and click OK. Click to define the thickness of the handle.

Maximize the Top viewport.

Run the Surface Tools > Remove A Control Point tool. Click the handle, then click to remove a row of control points. Re-run the tool to remove the rows of points inside the body.

To blend the handle with the body, we have a dozen possible options, and I’m just going to go ahead and use the one that I think works best for this particular case.

Run the Surface Tools > Offset Surface, click the handle surface, click ‘loose’ to maintain the structure of the surface in the offset, type 2 [enter]. I want the offset surface to fully intersect with the body surface, so adjust the offset accordingly. If you need to tweak it’s position a little, feel free.

Run Scale > Scale 1D and scale the offset surface to define the width of our blend. If you can’t tell what I’m doing just yet, give it a second and you’ll see.

Activate the Trim tool, select the handle offset, and use it to trim off the interior of the body. Draw a line across the handle. Run the Trim tool again, and use the line to trim it off.

Run Curve Tools > Adjustable Curve Blend. Click the edges to blend, and use the control points to adjust the bulge. Add a blend at the front and back of the handle.

Use the BlendCrv tool to create the center profile. Enable the ‘Edge’ parameter and click in the center of one of the trim edges to run the blend perpendar to the edge.

Run Surface > Sweep 2 Rails. Click the trimmed edges of the surfaces to use as ‘rail’ curves, and then select the cross-section blend curves. Hit ‘enter.’ Set the A and B rail continuity to Curvature, and click ‘OK.’

Select all three surfaces and click ‘join.’ In the ‘select’ palette, click ‘Curves.’ Hit ‘delete.’

Nice.

To add the trigger, we can just make use of the same geometry we used for the handle and the body.

Right-click the Explode tool to activate the ‘Extract’ command, and click the ‘Copy’ option in the command line. Select the handle slab, and hit [enter]. Drag the duplicate surface away from the body.

Maximize the front viewport.

Select Scale > Scale 1D, and scale it down to the width of the trigger.

Maximize the perspective viewport.

Move and rotate the new trigger surface into place. Switch to wireframe mode, and use the polyline tool to draw a curve that will cut back the surface to a more reasonable size. Select the curve, run the Trim tool, and click the excess trigger surface to trim ti down. Hit [delete] to delete the curve.

Select the trigger surface and run the Surface Tools > Offset tool. Click the ‘loose’ option and offset by 2mm.

Run the Trim tool and select the offset trigger and the blaster housing, then click to trim off the excess. Select the trimmed surfaces and join them.

Run Solid Tools > Variable Radius Fillet, and select the edges connecting the two bodies. Hit [enter], then adjust the radii at the end points. Make sure the RailType is set to DistBetweenRails for a nice, clean, even fillet surface. Hit [enter].

Use the Control Point Curve tool to draw a line to represet the trigger cutaway. Run ExtrudeCrv to extrude it upward to intersect with the trigger lip. Select the new surface and the rest of the blaster, then run the Trim tool. Click to trim off the excess.

Join the surfaces together.

Use FilletEdge to fillet the corner. If it doesn’t work correctly, it’s probably because the fillet geometry would intersect with another fillet. 9 times out of 10, if the fillet fails, try a smaller radius.

Run Select > Curves, and delete.

Cool! We have the beginnings of a space blaster! Stay tuned for more.

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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.