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Creating a Conch Shell

Author: Indigone

Tools Needed

* Hexagon 2.2 or higher

Support Files - None


We are going to create the surface of the conch shell using a double sweep. This tool builds a surface from one section and two profiles. The section will be a curve and the two profiles will be two nested helixes. We’ll then turn this into a 3-d shape that can have two shading domains, one for the inner shell, and one for the outer shell.

Step 1 - Create the First Helix

  1. First, turn on dynamic geometry. In the dynamic geometry panel, select Full DG.
  2. Make sure that the XY plane (the vertical plane) is the working plane.
  3. Click on the lines tab and the helix tool. In order to have the conch shell be accurate, we will use the properties palette to enter in exact values of the properties rather than free hand. Don’t let the mouse slide back into the viewing frame while doing this or the freehand tools will take over.
  4. Set the center to x=0, y=0, z=0 and click on apply.
  5. Set the radius to 5 and click on apply.
  6. Set the end radius to 0 and the height to 40 and click on apply.
  7. Set the slices to 6 and click on apply.
  8. Set the edges to 32 and validate.

This makes a long thin tapered helix (end radius 0) with 6 turns that will be the inner spiral of the conch. Make sure it stays in the same spot.


Step 2 - Create the Second Helix

  1. Click again on the lines tab and the helix tool.
  2. Set the center to x=0, y=0, z=0 and click on apply.
  3. Set the radius to 10 and click on apply.
  4. Set the end radius to 0 and the height to 12 and click on apply.
  5. Set the slices to 6 and click on apply.
  6. Set the edges to 32 and validate.

This makes a shorter, wider tapered helix 6 turns that will be the outer spiral of the conch. Make sure it stays in the same spot.


Step 3 - Join the Two Helixes at Their Endpoints

  1. Using the translate manipulator, slide the second (wider) helix straight up along the y axis. It’s important to keep them centered with each other, so be careful not to accidentally budge them along the x- or z-axis.
  2. Arrange the view so both end points can be seen clearly. Snap the two points together using the snap tool in the utilities tab. Click on the snap tool, then click on the end point of the first helix, and then click on the endpoint of the second helix. Use the shift key before clicking to be sure it has “snapped” to the vertex. The two helixes should now be joined.

Notice that their starting points of both helixes align nicely and lie directly on center the horizontal plane.


Step 4 - Create the Curve of the Shell

  1. Make sure that the XY plane is still the current plane. The curve should be parallel to the front plane. Arrange the view from the front so that both helixes’ starting points can be seen. This should be a nice curve from one starting point to the other. By selecting the front view and the XY plane, the new curve will be parallel to the vertical plane.
  2. On the lines toolbar, click on the interpolated curve. Hold down the shift-key and scroll you mouse over the starting point of the outer spiral until it “sticks”. Let go of the shift key and draw the curve. Be sure and click on 8 -10 turns of the curve, so that subtle changes can be made to it. When ready to connect to the inner spiral, hold the shift-key down again until it “sticks” and hit enter or validate the curve.
  3. Rotate the view to make sure the curve is connected to both helixes. If you select the curve in the scene palette, you’ll notice in the Dynamic Geometry palette that the curve control is still there. If you select that control in the Dynamic Geometry palette, you can adjust the curve.


Step 5 - Create the Surface of the Shell

  1. With the curve selected, on the surface modeling toolbar, click on the double sweep tool. The curve will be highlighted in green and you’ll be prompted to select the first profile.
  2. Click on one of the helixes, it will then be highlighted in red and you’ll be prompted to select the second profile.
  3. Click on the other helix and your surface will be formed.


Step 6 - Make Adjustments to the Shape

  1. Rename the surface from form0 to ConchSurface. If you select it in your scene palette, you’ll see that the dynamic geometry palette the surface is parent to the three curves (two helixes and a curve), and the curve is parent to its control. You can still make changes to the shape here.
  2. When you get the shape you like, click the lightning bolt next to the Conch Surface to collapse the dynamic geometry.


Step 7 - Make Further Adjustments to the Mesh

None of these adjustments are necessary, so you can skip this step, but they give the conch a bit more of a realistic look.

  1. By turning on the soft selection, you can make other nice adjustments to the conch’s surface. Open the flap a bit using a soft selection radius of 30.
  2. Using the free tessellation tool, smooth the sharp corner of the bottom of the shell.
  3. To close the top of the shell, truncate the pointy top, then switch to top view and with a soft selection radius of 3 pull the ends in to close it somewhat.
  4. Collapse any dynamic geometry that may have been created in your adjustments before moving on to step 8.


Step 8 - Create the Inner Shell

  1. To make an inner shell that can be shaded differently than the outer shell, use the offset tool on the surface modeling toolbar.
  2. Choose to have it inside with a value of .1 in the offset.
  3. Click to collapse the dynamic geometry. You should now have two forms in your scene palette, the inner shell and the outer shell. You can rename them in the properties palette.


Step 9 - Create a Surface Between the Inner and Outer Shell

Now close the tiny space between the two shells.

  1. Switch to the rear view and zoom in on the very bottom of the shell until you can see the two distinct surfaces to join.
  2. Use the ruled surface tool on the surface modeling toolbar. Select the tool then click on the edge of one surface, then the edge of the other. Validate. In the scene tab you’ll see that the two curves are now instances that are hidden, and the new surface has been formed. If you click on that new surface, you’ll see the dynamic geometry.
  3. Click to collapse the dynamic geometry.


Step 10 - Create Shading Domains

  1. Use the weld tool to weld together the outer surface with the connector we made in the last step. This way there will only be two shading domains, inner and outer.
  2. To create shading domains, click on each surface instance in the scene tab.
  3. In the shading domain palette click on the unassigned faces. When the faces become highlighted, click on “new”. Rename that domain.
  4. With the domain highlighted, in the materials palette you can change the name of the material and change the color. Since I will actually apply shaders in a different program, I picked some simple colors for the shaders in Hexagon.
  5. Repeat for each surface.


You’re now ready to export the object and use it! The last image is one that was done quickly in Carrara applying a fractal bump to the outer shell to put some texture on it. I’m sure with a good texture your conch will look perfect!

I hope you’ve learned something new with this tutorial. Happy modeling!