Main Supplement

Rope Modeling

Snap-Dragging a Rope
___ By Cecilia Ziemer
Open Carrara's Spline modeler's grid settings (Cmd/Ctrl-J), enter .50 in the Spacing field, and uncheck Snap to Grid. Make a .30 x .30 circle on the cross section plane. In Extrusion Preset: Spiral, give the spiral 14 turns, and accept the default length of 7 and distance to axis of 3.50.
___ Reopen the grid settings and enable Snap to Grid--(what follows will make you crazy without the snap). Using Director's camera in single window view, click and drag on the camera name and Set Position to left (the bottom line of the pop-up menu), then dolly in and adjust the camera for a good view of the bottom sweep path plane. The rows of points should be horizontal to the view.
___ There are three rows of points: top, bottom, and middle. We'll be moving points on the top and bottom rows using the middle only for center reference. It would be great if we could group 10 points on sweep path rows and rotate the groups +/- 90 degrees, but we can't. We're dragging one at a time--like parting hair the hard way.


___ Drag the first point on the right end of the bottom row up and to the right, letting it snap to the first vertical grid line past the center row, one grid space down from center. Drag the first point on the right end of the top row down and to the right, letting it snap to the same grid line--first vertical grid line past the center row and one grid space up from center.
___ This gives you an idea of what's about to happen. It's faster from now on to do one row at a time. Drag the second point on the bottom row to the vertical grid line and let it snap one space below the first point, then drag the third and let it snap just below the previous point. You can see that this begins to form another row. Continue the drags and snaps until you have a row of seven points below and at a right angle to the center row. Repeat the process for the remaining six points on the top row, dragging each to snap above the previous.
___ There are still 14 points to go on the left side. Starting again from the outer points, do what you did before, but now in mirror symmetry. Drag each point to the left, and let it snap to the first vertical grid line left of the center horizontal row of points.
___ When it's all over, the rows of points (or, row and two columns) will form an H shape. Take the rope back to Assemble, and shade it. I used Lost Horizon's Lumber Yard mapped in the Y-direction with perturbation set at 0 as the blend function in both color and bump channels.
___ Now that you're done with the snap-dragging, save the file, and sneak off to the park to smell the snapdragons, as there will be many cold winter days to come, a time for experimenting with endless variations on this rope spiral.

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Revised: 20 Aug 00
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