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FFD (Cyl) Space Warp

The Cylinder FFD uses a cylindrical array of control points in its lattice. This FFD is available as both an object modifier and a space warp. See FFD (Box/Cyl) Modifier for the object modifier version.

FFDs provide a method of deforming an object by adjusting the control points of a lattice. The offset position of the control points to the original lattice source volume cause the distortion of the affected object.

FFD space warps are created as separate objects in much the same way as you create a standard primitive, by dragging the mouse in the viewport. The result, however, is a lattice of control points. The source lattice of an FFD modifier, on the other hand, is fit to the geometry it’s assigned in the Stack. This might be a whole object, or a sub-object selection of faces or vertices.

Since FFD space warps are separate objects, they carry their own adjustable dimension parameters among the creation parameters.

You can apply object modifiers to space warp objects. As a result, you can use the Linked Xform modifier, for example, with a space-warp FFD.

Reference

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The dimension spinners are Radius and Height.

The spinners in the Set Number of Points dialog are labeled:

Side: The number of control points around the perimeter of the lattice.

Radial: The number of control points, radially, from the center to the outer perimeter.

Height: The number of control points along the height of the lattice.

(label): Displays the current number of controls points in the lattice. For example: 3x4x4.

Set Number of Points: Displays a dialog containing three spinners, labeled Length, Width, and Height, plus OK/Cancel buttons. Specify the number of control points you want in the lattice, and then click OK to make the change.

Note: Changes to dimension should be made before you adjust the positions of the lattice control points. When you change the number of control points with this dialog, any adjustments you’ve already made to the control points are lost. (You can undo this use of this dialog, however.)

Display Area

Affects the display of the FFD in the viewports.

Lattice: When this item is checked, lines are drawn connecting the control points to make a grid. Although the viewports can sometimes become cluttered when these extra lines are drawn, it helps to visualize the lattice.

Source Volume: When this item is checked, the control points and lattice are displayed in their unmodified state. This is an important display when you’re adjusting the source volume to affect specific vertices that lie within or without it. See the All Vertices and Only in Volume options, next.

Deform

Provides controls that specify which vertices are affected by the FFD.

Only In Volume: When this option is selected, only vertices that lie inside the source volume are deformed. Vertices outside the source volume are not affected.

All Vertices: When this option is selected, all vertices are deformed regardless of whether they lie inside or outside the source volumedepending on the value in the Falloff spinner. The deformation outside the volume is a continuous extrapolation of the deformation inside the volume. Note that the deformation can be extreme for points far away from the source lattice.

Falloff : This spinner, which is only enabled when All Vertices is chosen, determines the distance from the lattice that the FFD effect will decrease to zero. When this spinner is set to 0, it’s effectively turned off, and there is no falloffthat is, all vertices are affected regardless of how far they are from the lattice. The units of the Falloff parameter are actually specified relative to the size of the lattice. So a falloff of 1 means that the effect will go to 0 for points that are a lattice width/length/height away from the lattice (depending on which side they are).

Tension/Continuity: Lets you adjust the tension and continuity of the deformation splines. Although you can’t actually see the splines in an FFD, the lattice and control points represent the structure that controls the splines. As you adjust the control points, you likewise alter the splines (which move through each of the points). The splines, in turn, deform the geometry of the object. By altering the tension and continuity of the splines, you alter their effect on the object.

Selection

The buttons here provide additional methods of selecting the control points. You can toggle the state of any combination of the three buttons to select in one, two, or three dimensions at once.

All X, All Y, All Z : When one of these buttons is on and you select a control point, all control points along the local dimension specified by the button are selected as well. By turning on two buttons, you can select all control points in two dimensions.

About: Click this to display a dialog with copyright and licensing information.

How To

Example: An Animated Tablecloth

This example shows how to use the FFD (cyl) to animate a tablecloth that flies in and drapes itself over a table.

Begin by creating the table and tablecloth:

  1. Create a table from a couple of cylinders. Make the table top with a radius of about 30 units, and a height of about 2 units. Make the “table stand” cylinder with a radius of 3 and a height of 60.
  2. Make a tablecloth from a box that’s 100 units square, and 0.5 units in height. Increase its length and width segments to 30, and leave its height segments at 1.
  3. Position the tablecloth so it’s level with, or just slightly above the table top, and a little less than 100 units to the left of the table edge, as seen from the top view.
  4. Apply a nice wood grain to the table, and a checker to the tablecloth. (Set the checker tiling to about 15x15, and make the checkers any color you’d like.)
  5. Now, set up a cylindrical FFD space warp that will form the drape of the tablecloth over the table:

  6. Select FFD(cyl) from Geometric/Deformable Space Warps.
  7. In the Top viewport, create a cylindrical FFD space warp, centered on the table top, with a radius of 45, and a height of 5.
  8. Click the Set Number of Points button and, in the Set FFD Dimensions dialog, set the Side points to 12, the Radial points to 5, and the Height points to 2.
  9. Move the entire FFD lattice up until it’s just over the surface of the table, as seen from the Front viewport.

Next, adjust the control points of the lattice to drape over the table:

  1. Zoom Extents All Selected.
  2. In the Modify panel, click the Sub-Object button to access the control points.
  3. Turn on the All X button in the Selection area. This will let you select control points around the perimeter of the FFD cylinder.
  4. Select the Move tool and, in the Top viewport, region select the two visible control points of the two outer rings of control points at the nine-o’clock position. (This is easier shown than described. You can actually region select any number of vertices in the two outer concentric rings of vertices. Because All X is on, all of the control points for the two rings will be selected.)
  5. Press the SPACEBAR to lock the selection. In the Front viewport, drag the selected points halfway down the height of the table.
  6. Unlock the selection, and then region select any one of the control points in the outer ring to select all of the points in the outer ring.
  7. Lock the selection and, in the Front viewport, drag the outer ring of points down to the floor.
  8. You now have a truncated cone shape over the table.

  9. Unlock the selection. In the Top viewport, again select all the control points in the two outer rings.
  10. Scale the selected control points in, until the inner ring of points is slightly larger in radius than the table top.
  11. Select only the outer ring of points, and then scale them in so their radius is slightly larger than the inner ring.
  12. If necessary, move the position of the points, as seen from the Front viewport, down again to touch the floor.

    You now have a lattice of control points draped over the table.

In this next series of steps, you’ll bind the tablecloth to the FFD lattice, and then animate it to move over the table.

  1. Turn off Sub-Object mode.
  2. Click Bind to Space Warp, and drag between the FFD and the tablecloth.
  3. Select the FFD Lattice.
  4. Choose All Vertices in the Deform area.
  5. The tablecloth is immediately deformed because all vertices are now affected, including those outside of the lattice volume, and Falloff is set to 0.0, which means that the distance of the vertices from the lattice doesn’t matter. Any number greater than 0, however, will limit the effect.

  6. Set the Falloff spinner to 0.70.
  7. No longer influenced by the FFD space warp, the tablecloth returns to its square shape.

  8. Turn on the Animate button, and go to frame 100.
  9. In the Top viewport, select the tablecloth, and move it until it’s centered over the table.

  10. As the tablecloth nears the table, it first droops down to the floor, and then sweeps up and over the table, finally draping itself over the table.
  11. As you move the time slider back and forth and examine the animation, you might find that the bottom of the tablecloth is deformed to the point where it’s hanging below the floor. You can fix this by turning off the Animate button, going to frame 100, selected the lower ring of control points, and moving them up until the tablecloth is at the height you want it. You can also adjust the position of the other control points to create drapes, and so on.
  12. In the Display command panel, check Space Warps to hide the FFD space warp.
  13. Set up some appropriate lights and a camera, and play your animation.