# SpectrumFx Iwa

#### ● Overview

This effect produces a rainbow pattern like that of a thin film interference, according to the brightness
of the input image.
Even though the rainbow colors generated are not actually a thin film interference, similar results to
a glare material can be obtained.

#### ● Input port

- Source : Connect the source image. The brightness of the source image, corresponds to the
  thickness of the thin film.
  The brighter the luminosity, the thinner the film thickness will be. A luminosity of 0.0 corresponds to
  "Thickness Min" described later, and a luminosity of 1.0 corresponds to "Thickness Max".
- Light : Connect the light image.
  When a light image is connected, the output results are as follows:

- The Alpha channel of the output result is replaced with the alpha channel of the Light image.
- If the "Light Threshold" parameter described below is enabled, the Light image and the generated
  rainbow can be combined and output on the screen.

#### ● Parameters

- Intensity : The light intensity. The higher the value, the brighter the rainbow.
- Refractive Index : The refractive index of the medium. The higher the value, the brighter the
  rainbow.
- Thickness Max : Maximum thickness of the thin film. Corresponds to the film thickness of the
  low luminance portion of the Source image.
- Thickness Min : Minimum thickness of the thin film. Corresponds to the film thickness of the
  high luminance part of the Source image.
*Thickness can also take a negative value. In that case, all parts where the film thickness is negative
are calculated as zero.
*Thickness Min and Max can be reversed. In that case, the iridescent pattern will be reversed.
- R/G/B Gamma : Gamma correction value for each RGB channel of the rainbow pattern.
- Lens Factor : A gamma correction value that can be added when outputting a rainbow pattern from
  the luminosity of the Source image.
  This allows, for example, concentric patterns to be distorted through a convex / concave lens in the
  iridescent period.
- Light Threshold : When a Light image is connected, the Light image can be combined with the
  rainbow pattern on the screen.
  Light Threshold is the minimum Alpha channel value of the Light image required for screen composition.
  For each pixel, the following processing will be performed:

- When the alpha channel of the Light image is below the Light Threshold: Screen composition is not
  performed.
- When the alpha channel of the Light image is 1: The Light image is composited on the screen at 100%.
- When the alpha channel of the Light image is greater than the Light Threshold but less than 1: The
  screen composition ratio will be linearly interpolated.

The smaller the Light Threshold value, the larger the screen ratio with the Light image, so the output
image will be brighter. It can also accept negative values.