Point Curve

Point curves are NURBS curves whose points are constrained to lie on the curve.

• Create panel > (Shapes) > NURBS Curves > Object Type rollout > Point Curve button
• Standard menu: Create menu > NURBS > Point Curve
• Enhanced menu: Objects menu > NURBS and Patches > Point Curve

A point curve can be the basis of a full NURBS model.

Points lie on the curve they define.

Drawing Three-Dimensional Curves

When you create a point curve, you can draw it in three dimensions. There are two ways to do this:

• Draw In All Viewports: This toggle lets you use any viewport to draw the curve, enabling you to draw three dimensionally.
• Using Ctrl to drag points: While you draw a curve, you can use the Ctrl key to drag a point off of the construction plane.

With the Ctrl-key method, further mouse movement lifts the latest point off the construction plane. There are two ways to use this:

• Click-drag. If you hold down Ctrl and also hold down the mouse button, you can drag to change the height of the point. The point's location is set when you release the mouse button.

  This method is probably more intuitive.

• Click-click. If you Ctrl+click and then release the mouse button, the height changes as you drag the mouse. Clicking the mouse a second time sets the point's location.

  This method is less prone to repetitive stress injury.

While you are offsetting the point, a red dotted line is drawn between the original point on the construction plane and the actual point offset from the plane. You can move the mouse into an inactive viewport, in which case 3ds Max sets the height of the point using the point's Z axis in the inactive viewport. This lets you set the height of the point with accuracy.

Snaps also work when you change the height of a point. For example, if you turn on Point snapping, you can set a point to have the same height as another point by snapping to that other point in an inactive viewport.

Procedures

To create a NURBS point curve:

1. Go to the Create panel.
2. Activate (Shapes), and choose NURBS Curves from the drop-down list.
3. Turn on Point Curve.
4. In a viewport, click and drag to create the first point, as well as the first curve segment. Release the mouse button to add the second point. Each subsequent location you click adds a new point to the curve. Right-click to end curve creation.
   Note: If you begin the curve by clicking without dragging, this also creates the curve's first point. However, if you release the mouse button more than five pixels away from where you initially pressed it, this creates an additional point.

   While you are creating a point curve, you can press Backspace to remove the last point you created, and then previous points in reverse order.

   If Draw In All Viewports is on, you can draw in any viewport, creating a 3D curve.

   To lift a point off the construction plane, use the Ctrl key as described earlier in this topic under "Drawing Three-Dimensional Curves."

   As with splines, if you click over the curve's initial point, a Close Curve dialog is displayed. This dialog asks whether you want the curve to be closed. Click No to keep the curve open or Yes to close the curve. (You can also close a curve when you edit it at the Curve sub-object level.) When a closed curve is displayed at the Curve sub-object level, the initial point is displayed as a green circle, and a green tick mark indicates the curve's direction.

5. Adjust the curve's creation parameters.
6. (Optional.) To add a new NURBS curve sub-object, you can turn off the Start New Shape checkbox, and then repeat the preceding steps.

Interface

The creation parameters are the same for both point curves and CV curves.

Rendering rollout

Lets you turn on and off the renderability of the curve, specify its thickness in the rendered scene, and apply mapping coordinates.

Render parameters can be animated. For example, you can animate the number of sides.

Enable In Renderer

When on, the shape is rendered as a 3D mesh using the Radial or Rectangular parameters set for Renderer.

Enable In Viewport

When on, the shape is displayed in the viewport as a 3D mesh using the Radial or Rectangular parameters set for Renderer.

Use Viewport settings

Lets you set different rendering parameters, and displays the mesh generated by the Viewport settings. Available only when Enable in Viewport is turned on.

Generate Mapping Coords

Turn this on to apply mapping coordinates. Default=off.

The U coordinate wraps once around the thickness of the spline; the V coordinate is mapped once along the length of the spline. Tiling is achieved using the Tiling parameters in the material itself.

Real-World Map Size

Controls the scaling method used for texture mapped materials that are applied to the object. The scaling values are controlled by the Use Real-World Scale settings found in the applied material's Coordinates rollout. Default=on.

Viewport

Turn this on to specify Radial or Rectangular parameters for the shape as it will display in the viewport when Enable in Viewport is turned on.

Renderer

Turn this on to specify Radial or Rectangular parameters for the shape as it will display when rendered or viewed in the viewport when Enable in Viewport is turned on.

Radial

Displays the 3D mesh as a cylindrical object.

Thickness

Specifies the diameter of the viewport or rendered spline mesh. Default=1.0. Range=0.0 to 100,000,000.0.

Splines rendered at thickness of 1.0 and 5.0, respectively

Sides

Sets the number of sides (or facets) for the spline mesh n the viewport or renderer. For example, a value of 4 results in a square cross section.

Angle

Adjusts the rotational position of the cross-section in the viewport or renderer. For example, if the spline mesh has a square cross section you can use Angle to position a "flat" side down.

Rectangular

Displays the spline's mesh shape as rectangular.

Aspect

Sets the aspect ratio for rectangular cross-sections. The Lock checkbox lets you lock the aspect ratio. When Lock is turned on, Width is locked to Depth that results in a constant ratio of Width to Depth.

Length

Specifies the size of the cross–section along the local Y axis.

Width

Specifies the size of the cross–section along the local X axis.

Angle

Adjusts the rotational position of the cross-section in the viewport or renderer. For example, if you have a square cross-section you can use Angle to position a "flat" side down.

Auto Smooth

If Auto Smooth is turned on, the spline is auto-smoothed using the threshold specified by the Threshold setting below it. Auto Smooth sets the smoothing based on the angle between spline segments. Any two adjacent segments are put in the same smoothing group if the angle between them is less than the threshold angle.

Threshold

Specifies the threshold angle in degrees. Any two adjacent spline segments are put in the same smoothing group if the angle between them is less than the threshold angle.

Keyboard Entry rollout

The Keyboard Entry rollout lets you create a NURBS curve by typing. Use the Tab key to move between the controls in this rollout. To click a button from the keyboard, press Enter while the button is active.

X, Y, and Z

Let you enter the coordinates of the next point to add.

Add Point

Adds the point to the curve.

Close

Ends creation of the curve and creates a segment between the last point and the initial point to close the curve.

Finish

Ends creation of the curve, leaving it open.

Create Point Curve rollout

This rollout contains the controls for curve approximation.

Interpolation group

The controls in this group box change the accuracy and type of curve approximation used to generate and display the curve.

Draw In All Viewports

Lets you use any viewport while you are drawing the curve. This is one way to create a 3D curve. When off, you must finish drawing the curve in the viewport where you began it. Default=on.

While Draw In All Viewports is on, you can also use snaps in any viewport.