Blur compositing node

Blurs an image.

All

Parameters

Local variables

Example files

See also: Edge Blur, Radial Blur, Sharpen

This operation blurs an image. If a mask is used, it can be used as a normal mask, or it can alter the blur kernel per pixel to produce a more accurate blur.

Together with the Depth Of Field COP (providing the mask), this operation can do depth of field blurring.

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

Blur

X/Y Filter

Defines the blur kernel function.

Size

Defines the diameter of the blur for both X and Y.

Y Size

Turn on to adjust the diameter of the blur for Y independently of X ('Size' now controls X Size).

Units

Defines the units that the diameter of the blur is expressed in.

UV Coords	Values are expressed between 0 and 1, where 0 maps to a 1×1 blur (none) and 1 maps to xres x yres blur. This is resolution independent.
Pixels	The blur is expressed in pixels.

Per-Pixel Blur

If on, the mask affects the diameter of the blur at each pixel, rather than just blending the input with the output. This produces much more realistic blur transitions for grayscale masks, at a significant performance expense. The float value specifies the kernel size tolerance. By default this is set to 0.1, so only kernels evenly divisible by 0.1 will be used. Higher values blur faster, but tend to introduce ringing artifacts. Set to zero for completely accurate blurs (very slow for floating point masks).

Fast Blur

If on, the blur is done using a faster approximation technique. This option in only supported for Box, Bartlett (Cone) and Gaussian filters. The error is generally less than 1%, though for small filter widths (<10) it can be more significant (5-7%). Images with extremely high dynamic ranges may have higher error. For large filter sizes (1000’s), this technique is orders of magnitude faster than the mathematically accurate blurs.

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

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.

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.

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

Example files

Basic

$HFS/houdini/help/examples/nodes/cop2/blur/Basic.cmd

Load | Launch

This example demonstrates some of the blur filter types found in the Blur COP.

It also shows how two blur filter types can be combined and adjusted on individual X or Y axis.

Glow

$HFS/houdini/help/examples/nodes/cop2/blur/Glow.cmd

Load | Launch

This example demonstrates how to create a glowing effect using the Blur COP.

To do this, part of an image is extracted using luminance and brightened. This area is then blurred to simulate a glow and composited over the original image.

Mask

$HFS/houdini/help/examples/nodes/cop2/blur/Mask.cmd

Load | Launch

This example demonstrates how alpha masks can control the areas of an image the Blur COP will effect.

There are three different set ups, with various types of mattes to show how the Blur COP can be fine tuned.

Usages in other examples

Example name	Example for
BasicUses	Geokey compositing node	Load \| Launch
MakeShadow	Pin compositing node	Load \| Launch