Zcomp Node

The Zcomp node enables you to use both z-depth and alpha channel information to composite multiple layers of imagery. (If your images do not contain z-depth data, use the Mcomp node to do multilayer composites.)

The Zcomp node uses values contained in the z-depth channel of each input image to determine, for each pixel, the order in which that pixel will be layered in the composite. You can specify whether larger or smaller z-depth values are nearer to the camera.

Input Methods

The Zcomp node enables you to use one of two input methods, Combined or Split:

  • If you select the Combined input option, each layer of the composite must be a five-channel (RGBAZ) input image.
  • The Split input option enables you to use a pair of inputs for each layer, with the first input being a four-channel RGBA image and the second input being the Z channel for that image.
  • Note: If you are using the Split input style, each RGBA input must be followed in order by its associated z-depth channel input. If you disconnect one of the pair of inputs, the other input is automatically disconnected.

When using pairs of inputs in Split mode, the RGBA and Z images do not have to be the same bit depth. For example, you can use 8-bit RGBA inputs with floating point z-depth inputs. However, all of the RGBA inputs must be the same bit depth, and all of the Z inputs must be the same bit depth.

The Zcomp node accepts a virtually unlimited number of inputs, with a minimum of two inputs using Combined style or four inputs using Split style. The output of the Zcomp node is an RGBAZ image when using Combined style; when using Split style the output is RGBA.

Layers Parameter Tab

The Layers parameter tab enables you to specify the Z-Depth Order and Input Style to use. Be sure to set these two parameters to match your input data.

Each time you add an image to the Zcomp node, a corresponding layer is created in the Layers tab. Whether the image is a single input (RGBAZ image) or a pair of inputs (RGBA image and separate Z channel), only one new entry is added to the list.

Note:
When the Split input style is used, (RGBA image and separate Z channel), each layer will be labeled with the name of the RGBA input.

Z-Depth Order

You must set this parameter to match your z-depth channel data. If larger values represent pixels that are closer, use the default setting, select Larger Z is closer from the Z-Depth Order popup menu. On the other hand, if smaller values represent pixels that are closer, select Smaller Z is closer.

Input Style

You must set this parameter to indicate whether you are using a single input or a pair of inputs for each layer. The default setting, Split Color/Z-Depth , specifies that you are using pairs of inputs, with the information split between an RGBA input and a Z channel input. If you are using single RGBAZ inputs, select Combined Color/Z-Depth from the Input Style popup menu.

Preserve Input Sort Order

The Zcomp node uses z-depth data to determine the order in which each pixel will be layered in the composite. If the z-depth values for two pixels are equal, however, you may wish to specify that the input order of the layers be used to sort the pixels. The input order is the order in which the layers are listed in the Layers tab of the node panel, and this order can be changed by using the Up Arrow icons.

This option must be checked to ensure that the input order is retained. It is not active by default, however, because it slows performance of the Zcomp node.

Transparency

The Transparency parameter enables you apply a multiplier value to proportionally increase or decrease the opacity of the matte as a whole. The alpha channel value of each pixel is multiplied by the value set in this parameter. Therefore, the default value of 1 specifies that the input values of the alpha channel will be used for the matte.

Premultiplied Button

Click and hold the Premultiplied button to display a popup menu that enables you to specify whether the input image for that layer is premultiplied, not premultiplied, or Ultimatte. For more information, see the Premultiplication Status section of the Mcomp node description.

Up Arrow

You can quickly and easily reorder each layer in the list. Pressing the Up Arrow icon for a particular layer moves that layer one step closer to the top of the list. The top entry in the list of layers is actually the bottom, or background, layer of the composite.

Note:
The order of the layers in the list is superseded by the z-depth channel values. Therefore, the order of the layers is relevant only when z-depth values are equal and you have checked the Preserve Input Sort Order option.

Layer Checkbox

This feature lets you turn an individual input layer off and on without disconnecting and reconnecting the associated input image from the Zcomp node. Click the icon to toggle it to the opposite state. When the box is checked, the layer is enabled. When unchecked, the layer is disabled, and the associated Transparency parameter will be grayed out.

The background layer (top input) must be enabled; therefore, the checkbox for the background is grayed out.




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