Lumakey compositing node

Keys the image based on luminance (or similar function).

All Parameters Local variables

See also: Chromakey, Color Replace, Limit

This operation keys the image based on luminance (or similar function). It has an lower and upper bound, which may be both active at once. A pixel is keyed if it lies between the lower and upper bounds. If either bound is disabled, the pixel only needs to satisfy the other bound constraint (either be less than the Maximum Luminance, or greater than the Minimum).

The key is done on one of the input planes, and applied to all scoped planes. One of many luminance functions is applied to the input pixels, and the luminance value is compared to the bounds. The output plane is then multiplied by the computed key value.

A rolloff area may be used to soften the transition across the bound. An interpolation function is used to ramp down to black. The rolloff area begins at the Min or Max Luminance, and ends at a value greater than the Max Luminance or less than the Minimum Luminance, at a distance determined by the Rolloff parameter.

For sharp bound cutoffs, Super Sampling is used to antialias the edges. Multiple bilinear samples are run through the keyer to determine the final key value. To perform no supersampling, set Super Sample to 1. Super Sampling increases cook time exponentially, so while a value of 3 samples 9 subpixels, 8 samples 64. It is wise to keep the value of the Super Sample parameter under 5 unless you need extremely high quality edges.

Scoping

This operation may be restricted to certain planes, or components of planes. In addition, the operation may be applied to a subset of frames within the sequence. An image must have both its frame and plane scoped to be modified.

Images that are not modified are passed through, which does not take any memory or processing time.

Masking

This operation may be masked, which restricts the operation to an area of the image. The mask may be inverted, brightened or dimmed.

The mask input is on the side of the node. The label on the connector indicates the plane being used as a mask.

The mask input can also be scaled to fit the output image’s resolution, if they differ. However, if this node changes more often than the mask input, it is faster to place a Scale COP in front of the mask input to do the resize, as the resize will not occur on every cook of this node.

Parameters

LumaKey

Min Luminance

If on, this sets the lower limit for the key.

Max Luminance

If on, this sets the upper limit for the key.

Discard Keyed Region

If on, the keyed region is discarded.

Rolloff Region

The size of the rolloff region, in case a sharp edge is not wanted. This extends the keyed range by the rolloff size with a soft function.

Rolloff Function

Specifies the rolloff function of the rolloff region.

Luminance Function

Specifies how to prep the color to key off.

Supersample

The number of subpixels sampled per pixel in one direction (2 samples 4 pixels, 3 samples 9 pixels). More subsamples produce finer edges, at the cost of performance.

Key Plane

Specifies the plane to key. All scoped planes will be masked based on the result of the lumakey on this plane.

Mask

A mask can be chosen to limit the effect of the operator to areas defined by the mask. The mask can be taken from the mask input (side input) or from the first input itself.

Effect Amount

If no mask is present, this blends the output with the input by a constant amount (0 = all input, 1 = all output).

If a mask is present, this amount multiplies the mask.

Operation Mask

Selects the mask plane to use as a mask from the mask input. The mask can be selected from:

A mask can be a component of a plane or an entire plane. If a vector plane is supplied as a mask, its components are multiplied by the images' components.

Scalar Mask ('A', 'C.r')

C.r = I.r * M
C.g = I.g * M
C.b = I.b * M
Vector Mask ('C')

C.r = I.r * M.r
C.g = I.g * M.g
C.b = I.b * M.b

First Input

Useful for masking the operation to the image’s own alpha plane.

Mask Input

Selects the mask from the side mask input.

Off

Turns off masking, without requiring disconnection of the mask input (useful for temporarily disabling the mask).

Resize Mask to Fit Image

If the mask image is a different resolution than the output image, turning on this parameter will scale the mask to the output image’s resolution.

If this node is changing constantly, and the mask is not, it is somewhat faster to put a Scale COP down to do the resize for the mask image. Otherwise, the scale will occur every time this node cooks.

Invert Mask

Inverts the mask so that all fully 'masked' portions become unmasked. This saves you from inserting an Invert COP after the node with the mask.

Scope

Plane Scope

Specifies the scope for both the RGB components of Color, Alpha, and other planes. The (C)RGBA mask only affects Color components and Alpha. 'C' will toggle all the RGB components.

For planes other than Color and Alpha, the plane name (plus component, if applicable) should be specified in the string field. The pulldown menu can be used to select planes or components present in this node.

A plane is specified by its name. A component is specified by both its plane and component name. The '*' wildcard may be used to scope all extra planes. Any number of planes or components can be specified, separated by spaces.

Examples:

P
N.x N.y
P N Pz

Frame Scope

Frame Scope

Allows scoping of specific frames in the frame range. This is in addition to the plane scope (so a plane at a certain frame must be both plane scoped and frame scoped to be modified).

All Frames

All frames are scoped.

Inside Range

All frames inside a subrange are scoped.

Outside Range

All frames outside a subrange are scoped.

Even Frames

Even numbered frames are scoped.

Odd Frames

Odd numbered frames are scoped.

Specific Frames

A user-defined list of frames are scoped.

Frame Range

For Inside/Outside range, this parameter specifies the subrange of the sequence to scope (or unscope). This can be edited in Timeline viewer mode ( Ctrl + 2 in viewer).

Frame Dropoff

For Inside/Outside Range, this parameter specifies certain number of frames before and after to slowly ramp up to scoped. The operation will be blended with its input to 'ease in' or 'ease out' the scoping effect over a number of frames. This can be edited in Timeline viewer mode ( Ctrl + 2 in viewer).

Non-scoped Effect

For unscoped frames, this sets the blend factor between the input and modified images. Normally this is zero (use the input image). By setting this to a non-zero value, you can make unscoped frames be 'slightly' unscoped. The value can vary between 0 (unscoped) and 1 (scoped).

Frame List

The frame list for 'Specific Frames'. Frame numbers should be separated by spaces.

Automatically Adjust for Length Changes

If the sequence range changes, enabling this parameter will adjust the subrange and frame dropoff lengths to fit the new range.

Local variables

L

Sequence length

S

Start of sequence

E

End of sequence

IL

Input sequence length

SR

Sequence frame rate

NP

Number of planes in sequence

W,H

Width and height of image

I

Image index (0 at start frame)

IT

Image time (0 at start frame)

AI

Current plane array index

PI

Current plane index

PC

Num of channels in current plane

CXRES

Composite Project X resolution

CYRES

Composite Project Y resolution

CPIXA

Composite Project pixel aspect ratio

CDEPTH

Composite Project raster depth

CBP

Composite Project black point

CWP

Composite Project white point

Usages in other examples

Example name Example for
Glow

Blur compositing node

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Expand compositing node

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