Editing Splines


After you create a shape primitive, you can edit it by modifying its parameters, but the parameters for shapes are fairly limited. For example, the only parameter for the Circle shape is Radius. All shapes can be converted to Editable Splines, or they can have the Edit Spline modifier applied to them. Doing either enables a host of editing features. Before you can use these editing features, you must convert the shape primitive to an Editable Spline (except for the Line shape). You can do so by right-clicking the spline shape in the viewport and choosing Convert to image from book Convert to Editable Spline from the pop-up quadmenu, or by right-clicking on the Circle base object in the Modifier Stack and selecting Convert To Editable Spline in the pop-up menu. Another way to enable these features is to apply the Edit Spline modifier.

Editable Splines versus the Edit Spline modifier

After you convert the spline to an Editable Spline, you can edit individual subobjects within the spline, including Vertices, Segments, and Splines. There is a subtle difference between applying the Edit Spline modifier and converting the shape to an Editable Spline. Applying the Edit Spline modifier maintains the shape parameters and enables the editing features found in the Geometry rollout. However, an Editable Spline loses the ability to be able to change the base parameters associated with the spline shape.

Note 

When you create an object that contains two or more splines (such as when you create splines with the Start New Shape option disabled), all the splines in the object are automatically converted into Editable Splines.

Another difference is that the shape primitive base name is listed along with the Edit Spline modifier in the Modifier Stack. Selecting the shape primitive name makes the Rendering, Interpolation, and Parameters rollouts visible, and the Selection, Soft Selection, and Geometry rollouts are made visible when you select the Edit Spline modifier in the Modifier Stack. For Editable Splines, only a single base object name is visible in the Modifier Stack, and all rollouts are accessible under it.

Note 

Another key difference is that subobjects for the Edit Spline modifier cannot be animated.

Making splines renderable

Splines normally do not show up in a rendered image, but using the Renderable option in the Rendering rollout and assigning a thickness to the splines makes them appear in the rendered image. Figure 14.15 shows a rendered image of the Expeditions South logo after all shapes have been made renderable and assigned a Thickness of 3.0.

image from book
Figure 14.15: Using renderable splines with a Thickness of 3.0, the logo can be rendered

CROSS-REF 

The settings in the Rendering and Interpolation rollouts are the same as those used for newly created shapes, which were covered earlier in the chapter.

Selecting spline subobjects

When editing splines, you must choose the subobject level to work on. For example, when editing splines, you can work with Vertex (1), Segment (2), or Spline (3) subobjects. Before you can edit spline subobjects, you must select them. To select the subobject type, click the small plus sign icon to the left of the Editable Spline object in the Modifier Stack. This lists all the subobjects available for this object. Click the subobject in the Modifier Stack to select it. Alternatively, you can click the red-colored icons under the Selection rollout, shown in Figure 14.16. You can also select the different subobject modes using the 1, 2, and 3 keyboard shortcuts. When you select a subobject, the selection in the Modifier Stack and the associated icon in the Selection rollout turn yellow.

Note 

The Sub-Object button turns yellow when selected to remind you that you are in subobject edit mode. Remember, you must exit this mode before you can select another object

You can select many subobjects at once by dragging an outline over them in the viewports. You can also select and deselect vertices by holding down the Ctrl key while clicking them. Holding down the Alt key removes any selected vertices from the selection set.

After selecting several vertices, you can create a named selection set by typing a name in the Name Selection Sets drop-down list in the main toolbar. You can then copy and paste these selection sets onto other shapes using the buttons in the Selection rollout.

The Lock Handles option allows you to move the handles of all selected vertices together when enabled, but each handle moves by itself when disabled. With the Lock Handles and the All options selected, all selected handles move together. The Alike option causes all handles on one side to move together.

image from book
Figure 14.16: The Selection rollout provides icons for entering the various subobject modes. Segment subobject mode

The Area Selection option selects all the vertices within a defined radius of where you click. The Segment End option, when enabled, allows you to select a vertex by clicking the segment. The closest vertex to the segment that you clicked is selected. This feature is useful when you are trying to select a vertex that lies near other vertices. The Select By button opens a dialog box with Segment and Spline buttons on it. These buttons allow you to select all the vertices on either a spline or segment that you choose.

The Selection rollout also has the Show Vertex Numbers option to display all the vertex numbers of a spline or to show the numbers of only the selected vertices. This can be convenient for understanding how a spline is put together and to help you find noncritical vertices. The Selected Only option displays the Vertex Numbers only for the selected subobjects when enabled.

Figure 14.17 shows a simple star shape that was converted to an Editable Spline. The left image shows the spline in Vertex subobject mode. All the vertices are marked with small plus signs, and the starting point is marked with a small square. The middle image has the Show Vertex Numbers option enabled. For the right image, the vertex numbers are shown after the Reverse button was used (in Spline subobject mode).

image from book
Figure 14.17: Several spline shapes displayed with vertex numbering turned on Spline end point

At the bottom of the Selection rollout, the Selection Information is displayed. This information tells you the number of the spline (or segment) and vertex selected, or the number of selected items and whether a spline is closed.

Note 

The Soft Selection rollout allows you to alter adjacent non-selected subobjects (to a lesser extent) when selected subobjects are moved, creating a smooth transition. See Chapter 13, "Learning Modeling Basics and Working with Subobjects," for the details on this rollout

Controlling spline geometry

Much of the power of editing splines is contained within the Geometry rollout, shown in Figure 14.18, including the ability to add new splines, attach objects to the spline, weld vertices, use Boolean operations such as Trim and Extend, and many more. Some Geometry buttons may be disabled, depending on the subobject type that you've selected. Many of the features in the Geometry rollout can be used in all subobject modes. Some of these features do not even require that you be in a subobject mode. These features are covered first.

image from book
Figure 14.18: For Editable Splines, the Geometry rollout holds most of the features

Tip 

The quadmenu provides quick access to the main features for each subobject mode. After you are familiar with the various features, you can quickly access them through the quadmenu by simply right-clicking in the viewport

Create line

While editing splines, you can add new lines to a spline by clicking the Create Line button and then clicking in the one of the viewports. You can add several lines at the same time. Right-click in the viewport to exit this mode. Any new lines are their own spline, but you can weld them to the existing splines.

Break

Clicking the Break button and then clicking a vertex breaks the segment at that location by creating two separate end points. You can use the Break button in the Geometry rollout to add another vertex along a segment, thereby breaking the segment into two. You can also use the Break button in Vertex and Segment subobject modes.

Attach and Attach Multiple

The Attach button lets you attach any existing splines to the currently selected spline. The cursor changes when you're over the top of a spline that can be attached. Clicking an unselected object makes it part of the current object. The Reorient option aligns the coordinate system of the spline being attached with the selected spline's coordinate system.

For example, using the Boolean button requires that objects be part of the same object. You can use the Attach button to attach several splines into the same object.

The Attach Mult. button enables several splines to be attached at once. When you click the Attach Mult. button, the Attach Multiple dialog box (which looks much like the Select by Name dialog box) opens. Use this dialog box to select the objects you want to attach to the current selection. Click the Attach button in the dialog box when you're finished. You can use both the Attach and Attach Mult. buttons in all three subobject modes.

Note 

If the spline object that is being attached has a material applied to it, then a dialog box appears that gives you options for handling the materials. These options include Match Material IDs to Material, Match Material to Material IDs, or Do Not Modify Material IDs or Material. Applying materials is covered in Chapter 20, "Exploring the Material Editor."

Cross Section

The Cross Section button works just like the Cross Section modifier by creating splines that run from one cross-section shape to another. For example, imagine creating a baseball bat by positioning circular cross sections for each diameter change and connecting each cross section from one end to the other. All the cross sections need to be part of the same Editable Spline object, and then using the Cross Section button, you can click from one cross section to another. The cursor changes when the mouse is over a shape that can be used. When you're finished selecting cross-section shapes, you can right-click to exit Cross Section mode.

The type of vertex used to create the new splines that run between the different cross sections is the type specified in the New Vertex Type section at the top of the Geometry rollout.

Caution 

Although the splines that connect the cross sections are positioned alongside the cross section shape, they are not connected. You can use the Weld function to connect them.

After the splines are created, you can use the Surface modifier to turn the splines into a 3D surface.

Auto Welding end points

To work with surfaces, you typically need a closed spline. When you enable the Automatic Welding option in the End Point Auto-Welding section and specify a Threshold, all end points within the threshold value are welded together, thus making a closed spline.

Insert

The Insert button adds vertices to a selected spline. Click the Insert button, and then click the spline to place the new vertex. At this point, you can reposition the new vertex and its attached segments-click again to set it in place. A single click adds a Corner type vertex, and a click-and-drag adds a Bézier type vertex.

After positioning the new vertex, you can add another vertex next to the first vertex by dragging the mouse and clicking. To add vertices to a different segment, right-click to release the currently selected segment, but stay in Insert mode. To exit Insert mode, right-click in the viewport again or click the Insert button to deselect it.

Tutorial: Working with cross sections to create a doorknob

You can work with cross sections in several ways. You can use the Cross Section feature for Editable Splines, the Cross Section modifier, or the Loft compound object. All these methods have advantages, but the first is probably the easiest and most forgiving method.

To create a simple doorknob using the Editable Spline Cross Section button, follow these steps:

  1. Right-click any of the Snap toggle buttons on the main toolbar, and select Grid Points in the Grid and Snap Settings dialog box. Then click the Snap toggle button on the main toolbar (or press the S key) to enable grid snapping.

  2. Select the Create image from book Shapes image from book Circle menu command, and drag from the center grid point in the Top viewport to create a small circle. Repeat this step to create two more circles: one the same size and one much larger.

  3. Select the Create image from book Shapes image from book Rectangle menu command, and hold down the Ctrl key while dragging in the Top viewport to create a square that is smaller than the first circle. Repeat this step to create another square the same size. Aligning the squares is easier if you select the Center option in the Creation Method rollout.

  4. Click the Select and Move (W) button on the main toolbar, and drag the shapes in the Left viewport upward in this order: square, square, small circle, large circle, small circle. Separate the squares by a distance equal to the width of a door, and spread the circles out to be the width of a doorknob.

  5. Select the bottom-most square shape, and then right-click and select Convert To image from book Editable Spline in the pop-up quadmenu.

  6. In the Geometry rollout, click the Attach button and then select the other shapes to add them to the selected Editable Spline object.

  7. Rotate the Perspective viewport until all shapes are visible and easily selectable.

  8. Select the Linear option in the New Vertex Type section in the Geometry rollout, and then click the Cross Section button. Click the lowest square shape in the Perspective viewport, followed by the higher square shape, and then the lower small circle. This creates a spline that runs linearly between these lowest three cross-section shapes. Right-click in the Perspective viewport to exit Cross Section mode.

  9. Select the Bezier option in the New Vertex Type section, and then click the Cross Section button again. Click the lowest circle shape in the Perspective viewport, followed by the larger circle shape, and then the higher small circle. This creates a spline that runs smoothly between the last three cross-section shapes. Right-click in the Perspective viewport to exit Cross Section mode.

Figure 14.19 shows the splines running between the different cross sections. A key benefit to the Editable Spline approach is that you don't need to order the cross-section shapes exactly. You just need to click on them in the order that you want.

image from book
Figure 14.19: The Cross Section feature of Editable Splines can create splines that run between several cross-section shapes

Editing vertices

To edit a vertex, click the Vertex subobject in the Modifier Stack or select the vertex icon from the Selection rollout (keyboard shortcut, 1). After the Vertex subobject type is selected, you can use the transform buttons on the main toolbar to move, rotate, and scale the selected vertex or vertices. Moving a vertex around causes the associated spline segments to follow.

With a vertex selected, you can change its type from Corner, Smooth, Bézier, or Bézier Corner by right-clicking and selecting the type from the pop-up quadmenu.

Caution 

The New Vertex Type section in the top of the Geometry sets only the vertex type for new vertices created when you Shift-copy segments and splines or new vertices created with the Cross Section button. These options cannot be used to change vertex type for existing vertices.

Selecting the Bézier or Bézier Corner type vertex reveals green-colored handles on either side of the vertex. Dragging these handles away from the vertex alters the curvature of the segment. Bézier type vertices have both handles in the same line, but Corner Bézier type vertices do not. This allows them to create sharp angles.

Note 

Holding down the Shift key while clicking and dragging on a handle causes the handle to move independently of the other handle, turning it into a Bézier Corner type vertex instead of a plain Bézier. You can use it to create sharp corner points.

Figure 14.20 shows how the Bézier and Bézier Corner handles work. The first image shows all vertices of a circle selected where you can see the handles protruding from both sides of each vertex. The second image shows what happens to the circle when one of the handles is moved. The handles for Bézier vertices move together, so moving one upward causes the other to move downward. The third image shows a Bézier Corner vertex where the handles can move independently to create sharp points. The fourth image shows two Bézier Corner vertices moved with the Lock Handles and Alike options enabled. This causes the handles to the left of the vertices to move together. The final image has the Lock Handles and All options selected causing the handles of all selected vertices to move together.

image from book
Figure 14.20: Moving the vertex handles alters the spline around the vertex

The pop-up quadmenu also includes a command to Reset Tangents. This option makes the tangents revert to their original orientation before the handles were moved.

Refine

The Refine button lets you add vertices to a spline without changing the curvature, giving you more control over the details of the spline. With the Refine button selected, just click on a spline where you want the new vertex and one is added.

The Connect option makes a new spline out of the added vertices. This provides a method for copying part of an existing spline. When the Connect option is enabled, then the Linear, Closed, Bind First, and Bind Last options become enabled. The Linear option creates Corner type vertices resulting in linear segments. The Closed option closes the spline by connecting the first and last vertices. The Bind First and Bind Last options bind the first and last vertices to the center of the selected segment. Refine is available only for Vertex and Segment subobject modes.

Weld and Fuse

When two vertices are selected and are within the specified Weld Threshold, they can be welded into one vertex using the Weld button. Several vertices can be welded simultaneously. Another way to weld vertices is to move one vertex on top of another. If they are within the threshold distance, a dialog box asks whether you want them to be welded. Click the Yes button to weld them.

The Fuse button is similar to the Weld command, except that it doesn't delete any vertices. It just positions the two vertices on top of one another at a position that is the average of the selected vertices.

In Figure 14.21, the left image shows a star shape with all its lower vertices selected. The middle image is the same star shape after the selected vertices have been welded together, and the right image shows the star shape with the selected vertices fused. The Selection rollout shows five selected vertices for the fused version.

image from book
Figure 14.21: Using the Fuse and Weld buttons, several vertices in our star shape have been combined

You can use the Fuse button to move the selected vertices to a single location. This is accomplished by selecting all the vertices to relocate and clicking the Fuse button. The average point between all the selected vertices becomes the new location. You can combine these vertices into one after they've been fused by clicking the Weld button.

Connect

The Connect button lets you connect end vertices to one another to create a new line. This works only on end vertices and not on connected points within a spline. To connect the ends, click the Connect button and drag the cursor from one end point to another (the cursor changes to a plus sign when it is over a valid end point) and release it. The first image in Figure 14.22 shows an incomplete star drawn with the Line primitive, the middle image shows a line being drawn between the end points (notice the cursor), and the third image is the resulting star.

image from book
Figure 14.22: You can use the Connect button to connect end points of shapes

Make First

The Show Vertex Numbers option in the Selection rollout displays the number of each vertex. The first vertex is identified with a square around it. The Make First button lets you change which vertex you want to be the first vertex in the spline. To do this, select a single vertex and click the Make First button. If more than one vertex is selected, Max ignores the command. If the selected spline is an open spline, again Max ignores the command; an end point must be selected.

Note 

The vertex number is important because it determines the first key for path animations and where Loft objects start.

Cycle

If a single vertex is selected, the Cycle button causes the next vertex in the Vertex Number order to be selected. The Cycle button can be used on open and closed splines and can be repeated around the spline. The exact vertex number is shown at the bottom of the Selection rollout. This is very useful for locating individual vertices in groups that are close together, such as groups that have been fused.

CrossInsert

If two splines that are part of the same object overlap, you can use the CrossInsert button to create a vertex on each spline at the location where they intersect. The distance between the two splines must be closer than the Threshold value for this to work. Note that this button does not join the two splines; it only creates a vertex on each spline. Use the Weld button to join the splines. Figure 14.23 shows how you can use the CrossInsert button to add vertices at the intersection points of two elliptical splines. Notice that each ellipse now has eight vertices.

image from book
Figure 14.23: The CrossInsert button can add vertices to any overlapping splines of the same object

Fillet

The Fillet button is used to round the corners of a spline where two edges meet. To use the Fillet command, click the Fillet button and then drag on a corner vertex in the viewport. The more you drag, the larger the Fillet. You can also enter a Fillet value in the Fillet spinner for the vertices that are selected. The Fillet has a maximum value based on the geometry of the spline. Figure 14.24 shows the Fillet command applied to an eight-pointed star with values of 10, 15, and 20. Notice that each selected vertex has split into two.

image from book
Figure 14.24: The Fillet button can round the corners of a shape.

Note 

You can fillet several vertices at once by selecting them and then clicking the Fillet button and dragging the Fillet distance.

Chamfer

The Chamfer button works much like the Fillet button, except that the corners are replaced with straight-line segments instead of smooth curves. This keeps the resulting shape simpler and maintains hard corners. To use the Chamfer command, click the Chamfer button and drag on a vertex to create the Chamfer. You can also enter a Chamfer value in the rollout. Figure 14.25 shows chamfers applied to the same eight-pointed shape with the same values of 10, 15, and 20.

image from book
Figure 14.25: Chamfers alter the look of spline corners.

Tangent Copy and Tangent Paste

If you spend considerable time positioning the handles for the Bézier or Bézier Corner vertices just right, it can be tricky to repeat these precise positions again for other handles. Using the Tangent Copy and Tangent Paste buttons, you can copy the handle positions between different handles. To do so, simply select a handle that you wish to copy and click the Copy button, and then select the vertex to which you want to copy the handle and press the Paste button. The Paste Length button copies the handle length along with its orientation, if enabled.

Hide/Unhide All

The Hide and Unhide All buttons hide and unhide spline subobjects. They can be used in any subobject mode. To hide a subobject, select the subobject and click the Hide button. To unhide the hidden subobjects, click the Unhide All button.

Bind/Unbind

The Bind button attaches an end vertex to a segment. The bound vertex then cannot be moved independently, but only as part of the bound segment. The Unbind button removes the binding on the vertex and lets it move independently again. To bind a vertex, click the Bind button and then drag from the vertex to the segment to bind to. To exit Bind mode, right-click in the viewport or click the Bind button again.

For Figure 14.26, a circle shape is created and converted to an Editable Spline object. The right vertex is selected and then separated from the circle with the Break button. Then by clicking the Bind button and dragging the vertex to the opposite line segment, the vertex is bound to the segment. Any movement of the spline keeps this vertex bound to the segment.

image from book
Figure 14.26: The Bind button attaches one end of the circle shape to a segment.

Delete

The Delete button deletes the selected subobject. You can use it to delete vertices, segments, or splines. This button is available in all subobject modes. Pressing the Delete key when the subobject is selected has the same effect.

Show Selected Segments

The Show Selected Segs option causes any selected segments to continue to be highlighted in Vertex subobject mode as well as Segment subobject mode. This feature helps you keep track of the segments that you are working on when moving vertices.

Tutorial: Making a ninja star

If you're involved with fighting games, either creating or playing them, then chances are good that when you look at the Star primitive, you think, "Wow, this is perfect for creating a ninja star weapon." If not, then just pretend.

To create a ninja star using splines, follow these steps:

  1. Right-click any of the Snap toggle buttons on the main toolbar, and select Grid Points in the Grid and Snap Settings dialog box. Then click the Snap toggle button (or press the S key) on the main toolbar to enable grid snapping.

  2. Select the Create image from book Shapes image from book Circle menu command, and drag from the center grid point in the Top viewport to create a circle.

  3. Select the Create image from book Shapes image from book Star menu command, and drag again from the center of the Top viewport to center align the star with the circle. Make the star shape about three times the size of the circle, and set the number of Points to 10.

  4. With the star shape selected, right-click in the Top viewport and select Convert To image from book Editable Spline. In the Modify panel, click the Attach button, and click the circle shape. Then click the Vertex icon in the Selection rollout (or press 1) to enter Vertex subobject mode.

  5. Click the Create Line button in the Geometry rollout; then click the circle's top vertex and bottom vertex, then right-click to end the line, and right-click again to exit Create Line mode.

  6. Select the top vertex of the line that you just created (be careful not to select the circle's top vertex; you can use the Cycle button to find the correct vertex). Right-click the vertex, and select the Bézier vertex type from the quadmenu. Then drag its lower handle until it is on top of the circle's left vertex. Repeat this step for the bottom vertex, and drag its handle to the circle's right vertex to create a yin-yang symbol in the center of the ninja star.

  7. While holding down the Ctrl key, click on all the inner vertices of the star shape. Click the Chamfer button, enter the value of 15 in the Chamfer field, and press the Enter key.

Figure 14.27 shows the resulting ninja star.

image from book
Figure 14.27: The completed ninja star, ready for action (or extruding)

Editing segments

To edit a segment, click the Segment subobject in the Modifier Stack or select the segment icon from the Selection rollout to enter segment subobject mode. Clicking again on either exits this mode. Segments are the lines or edges that run between two vertices. Many of the editing options work in the same way as when editing Vertex subobjects. You can select multiple segments by holding down the Ctrl key while clicking the segments, or you can hold down the Alt key to remove selected segments from the selection set. You can also copy segments when they're being transformed by holding down the Shift key. The cloned segments break away from the original spline, but are still a part of the Editable Spline object.

You can change segments from straight lines to curves by right-clicking the segment and selecting Line or Curve from the pop-up quadmenu. Line segments created with the Corner type vertex option cannot be changed to Curves, but lines created with Smooth and Bézier type vertex options can be switched back and forth.

Several Geometry rollout buttons work on more than one subobject type.

Connect Copy

When you create a copy of a segment by moving a segment with the Shift key held down, you can enable the Connect Copy option to make segments that join the copied segment with its original. For example, if you have a single straight horizontal line segment, dragging it upward with the Copy Connect option enabled creates a copy that is joined to the original, resulting in a rectangle. Be aware that the vertices that connect to the original segment are not welded to the original segment.

Divide

When you select a segment, the Divide button becomes active. This button adds the number of vertices specified to the selected segment or segments. Figure 14.28 shows the diamond shape (second row, second from right) after all four segments were selected, a value of 1 was entered into the spinner, and the Divide button was clicked.

image from book
Figure 14.28: The Divide button adds segments to the spline.

Detach

The Detach button separates the selected subobjects from the rest of the object (opposite of the Attach button). When you click this button, the Detach dialog box opens, enabling you to name the new detached subobject. When segments are detached, you can select the Same Shape option to keep them part of the original object. The Reorient option realigns the new detached subobject to match the position and orientation of the current active grid. The Copy option creates a new copy of the detached subobject.

You can use Detach on either selected Spline or Segment subobjects.

Tutorial: Using Connect Copy to create a simple flower

Connect Copy is one of the features that you'll use and wonder how you ever got along without it. For this tutorial, we create a simple flower from a circle shape using the Connect Copy feature.

To create a simple flower using the Connect Copy feature, follow these steps:

  1. Select Create image from book Shapes image from book Circle, and drag in the Top viewport to create a simple circle shape.

  2. Right-click on the circle, and select Convert to image from book Editable Spline to convert the shape.

  3. In the Modifier Stack, select the Segment subobject mode (keyboard shortcut, 2) and enable the Connect option in the Connect Copy section.

  4. Select one of the circle segments, and with the Shift key held down, drag it outward away from the circle. Then repeat this step for each segment.

Figure 14.29 shows the results. With the Connect Copy option, you don't need to worry about the connecting lines.

image from book
Figure 14.29: The Connect Copy feature joins newly copied segments to the original.

Surface Properties

For segment and spline subobjects, you can access a Surface Properties rollout that lets you assign a Material ID to the subobject. These Material IDs are used with the Multi/Sub-object Material available in the Material Editor.

CROSS-REF 

You can find information on Material IDs in Chapter 21, "Creating and Applying Simple Materials."

Using the Select ID button and drop-down list, you can locate and select all subobjects that have a certain Material ID. Simply select the Material ID that you are looking for and click the Select ID button, and all segments (or splines) with that Material ID are selected. Beneath the Select ID button is another drop-down list that lets you select segments by material name. The Clear Selection option clears all selections when the Select ID button is clicked. If disabled, then all new selections are added to the current selection set.

Editing Spline subobjects

To edit a spline, click the Spline subobject in the Modifier Stack or select the spline icon from the Selection rollout. Transforming a spline object containing only one spline works the same way in subobject mode as it does in a normal transformation. Working in spline subobject mode lets you move splines relative to one another. Right-clicking a spline in subobject mode opens a pop-up quadmenu that lets you convert it between Curve and Line types. The Curve type option changes all vertices to Bézier type, and the Line type option makes all vertices Corner type. Spline subobject mode includes many of the buttons previously discussed as well as some new ones in the Geometry rollout.

Reverse

The Reverse button is available only for Spline subobjects. It reverses the order of the vertex numbers. For example, a circle that is numbered clockwise from 1 to 4 is numbered counterclockwise after using the Reverse button. The vertex order is important for splines that are used for animation paths or loft compound objects.

Outline

The Outline button creates a spline that is identical to the one selected and offset by an amount specified by dragging or specified in the Offset value. The Center option creates an outline on either side of the selected spline, centered on the original spline. When the Center option is not selected, then an outline is created by offsetting a duplicate of the spline on only one side of the original spline. To exit Outline mode, click the Outline button again or right-click in the viewport. Figure 14.30 shows an arc that has had the Outline feature applied. In the right image, the Center option is enabled.

image from book
Figure 14.30: The Outline button creates a duplicate copy of the original spline and offsets it.

Boolean

Boolean operations work with two or more splines that overlap one another. There are three different operations that can happen: You can combine the splines to create a single spline (union), you can subtract the overlapping area from one of the splines (subtract), or you can throw away everything except the overlapping area (intersection).

CROSS-REF 

You can also use Booleans to combine or subtract 3D volumes, which are covered in Chapter 18, "Working with Compound Objects."

The Boolean button works on overlapping closed splines and has three different options-Union, Subtraction, and Intersection-shown in Table 14.3. The splines must all be part of the same object. The Union option combines the areas of both splines, the Subtraction option removes the second spline's area from the first, and the Intersection option keeps only the areas that overlap.

Table 14.3: Boolean Button Options
Open table as spreadsheet

Button

Description

image from book

Union

image from book

Subtraction

image from book

Intersection

To use the Boolean feature, select one of the splines and select one of the Boolean operation options. Then click the Boolean button, and select the second spline. Depending on which Boolean operation you chose, the overlapping area is deleted, the second spline acts to cut away the overlapping area on the first, or only the overlapping area remains. To exit Boolean mode, right-click in the viewport.

Note 

Boolean operations can be performed only on closed splines that exist within a 2D plane.

Figure 14.31 shows the results of applying the Spline Boolean operators on a circle and star shape. The first image consists of the circle and star shapes without any Boolean operations applied. The second image shows the result of the Union feature, the third (circle selected first) and fourth (star selected first) use the Subtraction feature, and the fifth image uses the Intersection feature.

image from book
Figure 14.31: Using the Boolean operations on two overlapping shapes

Mirror

You can use the Mirror button to mirror a spline object horizontally, vertically, or along both axes. To use this feature, select a spline object to mirror and then locate the Mirror button. To the right of the Mirror button are three smaller buttons, each of which indicates a direction-Mirror Horizontally, Mirror Vertically, and Mirror Both-shown in Table 14.4. Select a direction, and then click the Mirror button. If the Copy option is selected, a new spline is created and mirrored. The About Pivot option causes the mirroring to be completed about the pivot point axes.

Table 14.4: Mirror Button Options
Open table as spreadsheet

Button

Description

image from book

Mirror Horizontally

image from book

Mirror Vertically

image from book

Mirror Both

Figure 14.32 shows a little critter that has been mirrored horizontally, vertically, and both. The right image was horizontally mirrored with the About Pivot option disabled. Notice that the eye spline was mirrored about its own pivot.

image from book
Figure 14.32: Mirroring a shape is as simple as selecting a direction and clicking the Mirror button.

Trim and Extend

The Trim button cuts off any extending portion between two overlapping splines. The splines must be part of the same object. To use the Trim feature, select the spline that you want to keep, click the Trim button, and then click the segment to trim. The spline you click is trimmed back to the nearest intersecting point of the selected object. This button works only in Spline subobject mode.

Figure 14.33 shows a circle intersected by two ellipse shapes. The Trim button was used to cut the center sections of the ellipse shapes away.

image from book
Figure 14.33: You can use the Trim button to cut away the excess of a spline.

The Extend button works in the reverse manner compared to the Trim button. The Extend button lengthens the end of a spline until it encounters an intersection. (There must be a spline segment to intersect.) To use the Extend command, click the Extend button and then click the segment to extend. The spline you click is extended. To exit Extend mode, right-click in the viewport or click the Extend button again.

The Infinite Bounds option works for both the Trim and Extend buttons. When enabled, it treats all open splines as if they were infinite for the purpose of locating an intersecting point.

Close

The Close button completes an open spline and creates a closed spline by attaching a segment between the first and last vertices. You can check which vertex is first by enabling the Show Vertex Numbers in the Selection rollout. This is similar to the Connect feature (accessible in Vertex subobject mode), but the Connect feature can connect the end point of one spline to the end point of another as long as they are part of the same Editable Spline object. The Close feature works only in Spline subobject mode and connects only the end points of each given spline.

Explode

The Explode button performs the Detach command on all subobject splines at once. It separates each segment into a separate spline. You can select to explode all spline objects to separate Splines or Objects. If you select to explode to Objects, then a dialog box appears asking you for a name. Each spline uses the name you enter with a two-digit number appended to distinguish between the different splines.

Tutorial: Spinning a spider's web

Now that you're familiar with the many aspects of editing splines, let's try to mimic one of the best spline producers in the world-the spider. The spider is an expert at connecting lines together to create an intricate pattern. (Luckily, unlike the spider that depends on its web for food, we won't go hungry if this example fails.)

To create a spider web from splines, follow these steps:

  1. Select Create image from book Shapes image from book Circle, and drag in the Front viewport to create a large circle for the perimeter of the web (let's pretend that the spider is building this web inside a tire swing). Right-click on the circle, and select Convert To image from book Editable Spline to convert the circle shape.

  2. Select the Spline subobject in the Modifier Stack (or press the 3 key) to enter Spline subobject mode.

  3. Click the Create Line button in the Geometry rollout, and click in the center of the circle and again outside the circle to create a line. Then right-click to end the line. Repeat this step until 12 or so radial lines extend from the center of the circle outward.

  4. While you're still in Create Line mode, click on the circle's center and create lines in a spiral pattern by clicking on each radial line that you intersect. Right-click to end the line when you finally reach the edge of the circle. Then right-click again to exit Create Line mode.

  5. Select the circle shape, and click the Trim button. Then click on each line segment on the portion that extends beyond the circle. This trims the radial lines to the edge of the circle. Click the Trim button again when you are finished to exit Trim mode.

  6. Change to Vertex subobject mode by clicking Vertex in the Modifier Stack (or by pressing 1). Then select all the vertices in the center of the circle, and click the Fuse and Weld buttons.

Figure 14.34 shows the finished spider web. (I have a new respect for spiders.)

image from book
Figure 14.34: A spider web made from Editable Splines




3ds Max 9 Bible
3ds Max 9 Bible
ISBN: 0470100893
EAN: 2147483647
Year: 2007
Pages: 383

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