Houdini 22.0 Nodes Copernicus nodes

Fast Fourier Transform Copernicus node

Computes the Fourier transform of an image.

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Since 22.0

This is a low-level utility node that computes the Fourier transform of an image, converting pixel values from the spatial domain into frequencies (or vice verse). In essence, the forward transform decomposes the image into a sum of simple waves; and the inverse transform reconstructs an image given the waves that make it up. You can use the Fourier transform to perform frequency-space manipulations of the image, such as blurring or sharpening.

Note

The Fourier transform relies on complex numbers , and the node has inputs and outputs for real and imaginary components of the signal. When performing the forward transform of an ordinary image, you may feed it into the real port and ignore the imaginary input. However, the inverse transform will require both of these components to reconstruct the image.

Parameters

FFT Direction

Selects whether to perform the forward or the inverse transform. Forward FFT converts an image into frequency space, while Inverse FFT reconstructs an image from its frequencies. To perform the Forward FFT of an image, you can plug it into the real input.

Center DC

When enabled, the low-frequency components of the spectrum are shifted to be at the center of the image. If Center DC is disabled, center of the image contains the high frequencies, and the low frequencies are at the corners.

Normalize on Forward Pass

When this checkbox is turned on, normalization is applied during the forward transform. When disabled, normalization happens during the inverse pass. Turning this option on allows for easier visualization of the power in the spectrum. Value of this parameter must match on nodes that perform forward and inverse passes for faithful reconsturction.

Target Sum

When enabled, rescales the spectrum such that the sum of all pixel values after the inverse pass will work out to Target Sum.

Inputs

real

Real component of the input signal. For the forward transform, this is the only required input.

imaginary

Imaginary component of the input signal. This must be present to produce a purely real output when calculating the inverse transform.

Outputs

real

Real part of the output.

imaginary

Imaginary component of the output.

See also

Copernicus nodes