Houdini 11 Nodes Compositing nodes

Detects illegal pixels, like NAN and INF, in images.

Shaders and renderers can generate illegal floating point values every once in a while. This operation detects bad pixels, specifically NAN and INF, and either highlights them or fixes them. It can also notify you through a warning or an error which frame and plane have bad pixels.

Because the data is missing from that pixel, it can be zeroed out or replaced by blending together surrounding pixels. When zeroing pixels, the entire pixel is zeroed even if only one component is bad (to avoid color shifting).

If pixels are replaced, and only a part of the pixel’s components is bad, only that component will be replaced. If a large block of bad pixels is present, it will attempt to iterate up to 16 times to break down the block. Large blocks will look like blurry spots in the image, so you may want to limit the number of bad pixels to replace.

Note

Bad pixels are only detectable in floating point formats (16 and 32 bit floating point). Integer formats will have already been quantized to a valid (but possibly random) color in the renderer, making them impossible to detect.

Note

Bad pixels will not be detected in planes or areas of the image that are not used during the cook.

Parameters

Illegal Pixel

Illegal Pixels

Illegal pixels can be flagged or fixed. Often, flagging is used to debug the shader, while fixing is used to attempt to continue with the image as-is.

“Fix by Blending Surrounding Pixels”

For small numbers or isolated pixels, this method will work well to fix the image.

“Fix by Zeroing”

This method clears the NANs so that downstream compositing operations behave, but doesn’t do much in the way of visually correcting the image.

“Show by Highlighting”

Shows bad pixels by highlighting them super-red (20,0,0).

“Show by Isolating”

Shows bad pixels by highlighting them and clearing all correct pixels.

Notification

If a bad pixel is found, this operation can raise a warning or an error.

“None”

The node is not flagged with an error or warning, though the number of bad pixels is still reported in the node info.

“Warning”

A warning flag is posted with the number of bad pixels in the node info.

“Error”

An error is raised. The number of bad pixels is printed in the node info, but it may not be entirely accurate because this will terminate the cook, and no more tiles will be processed.

“Error if Over Limit”

An error is raised if the number of bad pixels in a single plane is greater than the limit specified. Otherwise, a warning is raised.

“Bad Pixel Limit”

The number of acceptable bad pixels. If more than this number are in the image, the cook will halt.

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