Subdivision

The Effect->Subdivision command in the Model module allows you to subdivide polygons of a polygon mesh object or subdivide a NURBS curve or surface. Depending on whether you select a polygon mesh or a NURBS, different dialogue boxes are displayed.

Polygon Mesh Objects

Adding polygons increases the resolution of the polygon mesh object. This is especially useful for deformation or lattice operations.

When you subdivide polygon mesh objects, the overall effect is to add edges; for instance, out of 1 polygon with 4 edges, you can get 2 polygons and 7 edges.

Procedure

1. Select a polygon mesh object.
2. Choose the Effect->Subdivision command.
   
   The Polygon Subdivision dialogue box is displayed.
   
   
3. Set the number of Subdivisions desired for each axis.
4. Click Ok to exit the dialogue box or Cancel to exit without accepting the settings.

NURBS Curves and Surfaces

When you select either a NURBS curve or surface, you can choose one or more spots on the curve or surface at which to subdivide. You can also specify the degree of continuity that is applied to the new points on the curve.

Technically, you are really editing the continuity of knots on the curve or surface, but since these are not visible in the display, it is done by interacting with the curve's control points.

Regardless of the degree of continuity you choose, the shape of the curve or surface remains the same when subdivided. However, as you move the new control point, the degree of continuity selected determines the shape and relative smoothness of the new curve segment.

 

NURBS Curves

1. Select a NURBS curve.
2. Choose the Effect->Subdivision command.
   
   The NURBS Curve Subdivision dialogue box is displayed.
   
   
3. Use the Location slider to choose the appropriate spot to subdivide.
4. Select the degree of continuity for the new control point. The maximum value of the slider depends on the degree of the curve: for linear, 0 only; for quadratic, 0 or 1; for cubic degree, 0, 1 or 2.
   
   If you enter an invalid value (such as 4), it is ignored and the maximum value for the current curve is used instead.
   
   
5. Click Subdivide to apply the operation, then Exit to exit the dialogue box, or click Cancel to exit without accepting the settings.

Parameters

Interactively adjusts the position along the curve at which to subdivide. The currently selected position is indicated by a magenta point.

Sets the continuity of the new control point.

• C0: Positional continuity. As you move the control point, the curve is interpolated exactly on the point, which creates a pointy effect.
• C1: Positional and tangential continuity. As you move the control point, it moves increasingly away from the curve, creating a smoother curve shape.
• C2: Positional, tangential, and curve continuity. As you move the control point, it moves increasingly away from the curve, creating a high degree of smoothness.

Applies the settings without exiting the dialogue box. You can choose a different location and repeat the operation.

 

NURBS Surfaces

1. Select a NURBS surface.
2. Choose the Effect->Subdivision command.
   
   The NURBS Surface Subdivision dialogue box is displayed.
   
   
3. Select the direction (U, V, or U & V) along which to subdivide the surface. A magenta curve appears showing your choice.
4. Use the Location slider to position the curve along a surface.
5. Select the degree of continuity for the new control point. The maximum value of the slider depends on the degree of the surface: for linear, 0 only; for quadratic, 0 or 1; for cubic degree, 0, 1, or 2.
   
   If you enter an invalid value (such as 4), it is ignored and the maximum value for the current curve is used instead.
   
   
6. Click Subdivide to accept the settings, then Exit to exit the dialogue box, or click Cancel to exit without accepting the settings.

Parameters

Interactively adjusts the position for the subdivision along u, v, or both u and v. The currently selected position is indicated by a magenta curve.

Sets the continuity of the new control point.

• C0: Positional continuity. As you move the control point, the surface is interpolated exactly on the point, which creates a pointy effect.
• C1: Positional and tangential continuity. As you move the control point, it moves increasingly away from the surface, creating a smoother surface shape.
• C2: Positional, tangential and surface continuity. As you move the control point, it moves increasingly away from the surface, creating a high degree of smoothness.

Selects the direction(s) along which to subdivide the surface.

Applies the settings without exiting the dialogue box. You can choose a different location and repeat the operation.

Last updated 02-apr-1998