Rotospline NodeThe Rotospline node enables you to create and manipulate matte shapes with precision and control. Most commonly this functionality is used to create garbage mattes. Garbage mattes are used to remove unwanted elements from an image before compositing it with other imagery. For example, a garbage matte could be used to remove lights or other equipment from a bluescreen shot before the subject was composited over a background scene. A Rotospline matte can also be used as a "stencil," or mask; that is, to isolate a portion of an image for further manipulation such as color correction. For example, a matte could be drawn to isolate an automobile that was filmed in black-and-white, thus enabling you to colorize only the car while leaving the background monochrome. The Rotospline node can be used to create a control image, or mask, for another node, such as Vector Warp or Color Correct. The Rotospline node features a work monitor that provides you with tools for drawing matte shapes around portions of an image. You can edit, scale, rotate, invert, duplicate, and animate these shapes. The drawing tools enable you to draw both straight (linear) and curved (spline) line segments. You control the splines by dragging handles that extend from the spline's anchor points. You can display the source image in the work monitor, to use as a reference when drawing a shape that will be used to isolate a specific object or area in the image, or you can display the matte channel only. The Rotospline work monitor also enables you to access a key frame editor to set and delete key frames to control the interpolation of shape characteristics over time. You can create as many matte shapes as you need for an image, and for each shape you can set different parameter values (such as frame range, opacity, and edge characteristics). You can also invert the pixel values of any shape, and use it as a cutout to punch a hole in another shape. And you can change the order in which the shapes are layered. The Rotospline node accepts one input, which may or may not have an alpha channel:
The node output is either an RGBA or a one-channel (alpha) image, as you specify. Using the Rotospline Work MonitorIn addition to the standard Monitor Toolbar, the Rotospline work monitor panel provides a shape panel with controls for creating and editing shapes. The shape outlines are displayed over the input imagery in the image area of the work monitor. ![]() Rotospline Shape PanelThe Rotospline shape panel consists of three sections:
![]() Shape ListThe Shape list displays a list of every shape you create. As soon as you create or replicate a shape, a new entry appears in the list. Select ShapeClick the Select Shape button to make the corresponding shape the active shape. All of the other parameter settings in the panel apply to the currently selected shape. Up ArrowThe top entry in the Shape list is the bottom layer of the matte image. Each time you create a new shape, that shape is layered over any previous shapes. The Up arrows are used to reorder the list, and consequently the order of the shapes themselves. The order in which shapes are layered affects how overlapping shapes interact. Click the Up icon for a shape to move that shape one step closer to the top of the list, which is one layer back in the image. NameYou can use the Name field to assign descriptive names to shapes. Simply select the current name, key in a new name, and press the Enter key. Delete ShapeClick the Delete Shape button to delete the corresponding shape. Both the shape and the list entry are deleted. Shape CharacteristicsThese parameters apply to the currently selected shape. You can select another shape and apply a different set of values to the same parameters. Opacity, Edge, and Gamma values can all be animated over time by clicking the associated STED button to access the Chalice Space-Time Editor. For more information, see chapter 9, "Space-Time Editor (STED) ." RangeThis parameter enables you to specify a range of frames in which the currently selected shape will appear by keying a starting and ending frame number into the data entry fields. OpacityThis parameter enables you to set the opacity (or relative transparency) of the currently selected shape. A setting of 1 shows pure white (completely opaque) inside the matte; a setting of 0 shows pure black (completely transparent) inside the matte; intermediate values show shades of gray. You can set the Opacity parameter by keying in a numerical value between 0 and 1 or by using the mouse to set the tuner to the desired value. The default value is 1. Edge TypeThis parameter controls the softness, or blur, of the matte edge of the currently selected shape. Select one of three options from the Edge Type popup menu: No EdgesObviously, this option (the default) specifies that no blurring be applied to the edges. Uniform EdgesThis option blurs every edge evenly by the value you enter in the associated tuner, which only becomes active when this option is selected. A value of 0 generates no blurring and a value of 1 produces an extremely soft, blurred edge that is 10 percent of the total width of the image. Nonuniform EdgesThis option enables you to apply a different edge to each spline. This parameter is a special case, in that (unlike the Uniform edge option):
With Edge Mode selected, the points of the selected shape change appearance (they look like hollow squares) to indicate that they can be manipulated to set the width and direction of the edge blur. Simply drag one of these "edge points" to a new position and examine the resulting blur. When you select another mode, such as Point Mode, you will see that the actual anchor point of the spline has not moved from its original position. InvertClick the checkbox of this shape-specific parameter to invert the pixel values of the matte (e.g., white changes to black, and vice-versa).
Shape ToolsThe Shape Tools section features nine buttons that control the drawing and editing tools and open the Rotospline key frame editor. ![]() Draw Mode (Alt D)Draw Mode enables you to draw straight (linear) and curved-line (spline) segments. When you open the Rotospline work monitor for the first time, Draw mode is selected by default (once you have created a shape, the monitor defaults to Point Mode when opened). Click the Draw Mode button to enter Draw Mode.
Point Mode (Alt P)Click the Point button to enter Point Mode. Point Mode enables you to reposition anchor points to adjust the paths of shape segments you create using the other drawing tools. Click and drag any anchor point or slope handle to reposition it, or use the arrow keys on your keyboard to translate the selected point or handle in 1-pixel increments: the Up arrow key moves the point or point handle up a pixel, the Right arrow moves it a pixel to the right, and so forth. You can zoom in to position the anchor points more precisely, if necessary, by clicking the Zoom button on the monitor toolbar. ![]()
Shape Mode (Alt S)Click the Shape button to enter Shape Mode. Shape Mode enables you to work with shapes as a whole. You can translate, scale, and rotate the selected shape in this mode. When you click on an established path or shape, Chalice displays a control device that features a boundary box and a circle-with-crosshairs tool: ![]()
![]() Add Point Mode (Alt V)Add Point Mode enables you to add new anchor points to the shape. Click the Add Point button to enter Add Point Mode. Then click on an established path to add a new point to the shape.
Edge Mode (Alt E)The Edge Mode button only becomes accessible when the Nonuniform Edges option is selected from the Edge Type menu, which is described in the previous section on "Shape Characteristics." In Edge Mode the points of the selected shape become hollow squares. Any of these "edge points" can be moved by dragging the mouse to adjust the edge blur for the associated spline.
Delete Point / Shape (Del)Delete Point/Shape button enables you to delete selected anchor points and shapes:
Replicate Shape (Alt R)Replicate Shape mode enables you to create additional copies of a shape. When you click the Replicate Shape button, Chalice replicates the selected shape, and creates a new, untitled entry in the Shape List. The shape is copied whether the entire shape is selected, or just a single anchor point of the shape. Expand Points (Alt O)The Expand Points button enables you to transform linear segments into splines . While in Point Mode, click on a straight-line anchor point to select it. Then click the Expand Points button. Chalice transforms the point into a spline anchor point and any linear segment connected to the point becomes a spline. Compress Points (Alt C)The Compress Points button enables you to transform splines into linear segments . While in Point Mode, click on a spline anchor point to select it. Then click the Compress Points button. Chalice transforms the point into a straight-line anchor point and any spline connected to the point becomes a linear segment. Keyframe EditorYou click the Keyframe Editor button to access the Rotospline Keyframe Editor. ![]() A key frame for a shape is created automatically whenever you move to a new frame in a sequence and modify the shape in any way. The node performs a linear interpolation of the shape characteristics and associated parameter values for the frames between each key frame. The Rotospline Keyframe Editor displays, in graph form, all key frames for a selected shape. The Keyframe Editor is the most convenient and precise way to create, move, and delete key frames in a sequence:
The editor displays key frame data for the currently selected shape only. To view and modify key frames for another shape, select that shape from the Shape list in the node panel. The editor graph will update to display the key frame data for the new shape.
By default, when you open the Keyframe Editor, a graph displays the entire range of frames in the sequence. You can adjust the graph display range by keying new start and end frame values into the text entry fields. The scroll bar enables you to navigate back and forth through the graph display. Rotospline Parameter Tab![]() Work Monitor / At ResolutionFirst, select a display resolution for the work monitor from the At Resolution popup menu. Then click the plus icon to display the work monitor for this node. The functionality of the Rotospline monitor drawing and editing tools is described in the previous section, "Using the Rotospline Work Monitor ." Display AsThe Display As popup menu provides three options to control the display of matte shapes in the Alpha channel view of the work monitor. (In RGB view, matte shapes always display in wireframe mode to enable you to see the image behind them.) The edge settings you specify for each shape in the work monitor are used for the final output. The Display As options affect only how the shapes are displayed in the work monitor:
Channels OutThe Channel parameter enables you to specify whether the node should output an RGBA image, or the Alpha channel only. Anti-AliasThe Anti-Alias popup menu enables you to specify the level of anti-aliasing to apply, if any, to the shapes you draw in the work monitor. The higher the setting, the smoother the splines will be displayed and rendered. Of course, higher settings also take correspondingly longer to process. Incoming AlphaThe Incoming Alpha popup menu enables you to specify the characteristics of the alpha channel data used by the Rotospline node:
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