• Presets from outside your user preferences directory (for example, the “factory” presets that ship with Houdini in $HFS) are “read only”. Their names are displayed in italics. They cannot be deleted, and if you try to edit one, Houdini will create a new temporary theme with your edits.

• You can click a theme’s menu button (to the right of the theme name in the theme list). You can also right-click a theme to get the same menu.

• Houdini sometimes creates “temporary” themes:

  • If you try to edit a read-only theme, Houdini creates a new theme with your edits.

  • If the saved theme doesn’t match any known themes.

    This can happen if you clicked Accept with an edited theme, but didn’t save your changes first. Or, if you set one of your themes as the application theme, then delete the theme. In these cases the temporary theme is named Untitled Theme.

  • The Random button generates a random theme in a new temporary preset, unless the currently selected theme was generated from the Random button.

  To save a temporary theme, click the theme’s menu button (to the right of the theme name in the theme list) and choose Save As. (If you are on one of the tabs other than Presets so the window is wide, you can also click the Save As button at the bottom of the window.)

• Themes with unsaved changes and temporary themes have a bullet (•) next to their names in the theme list.

• Houdini stores the files corresponding to your user themes in $HOUDINI_USER_PREF_DIR/config/Themes. To show the file for a theme, click the theme’s menu button (to the right of the theme name in the theme list) and choose Reveal File.

== Editing a theme === (edit)

• Click the Swatches or Sliders tab to show the full editor.

  • The Swatches interface is a quick way to select colors by choosing from a curated palette.

  • The Sliders interface gives full control over

• Use the controls on the right side to edit the base, accent, and highlight colors.

• To revert to the most recently saved version of the current theme, click the Revert button at the bottom of the window.

• To save the current settings to the selected theme, click the Save button at the bottom of the window.

• If the selected preset is read-only, Houdini will create a new preset entry to save into.

Houdini derives the full palette of user interface colors from three main colors you choose. It applies various heuristic rules when deriving to maintain contrast and readability.

Basically, you set the main colors to influence the overall look of the theme. Because most interface colors are derived from one of the main colors, or combinations of main colors, you may not see the unaltered main colors in many places.

The three main colors are:

The controls on the Tweaks tab let you change which color is used for some interface elements, such as checkboxes and selected tabs.

On a television, the “contrast” control moves all colors toward or away from neutral gray. However, for themes, “contrast” only controls the contrast level of colors derived from the main colors. It does not affect the main colors.

Individual themes have their own Theme contrast control on the tweaks tab. The global scale is applied on top of the theme scale. This can be useful if you want a certain theme to have lower or higher contrast than other themes.

You can also increase or decrease the contrast of text separately on the tweaks tab.

• For each of Base, Accent, and Highlight, click a hue circle, then click a swatch from a grid where the columns have different lightness and the rows have different chroma.

• You can click the color swatch on the right to choose the color using Houdini’s standard color editor.

• Click in the color circle to set the hue and chroma, or edit the values using the sliders.

• You can click the color swatch on the right to choose the color using Houdini’s standard color editor.

• The theme editor uses a color model based on OkLCH. It is designed to account for perceptual color differences, so colors with the same Lightness value should have the same apparent brightness to the human eye. This system is not perfect but provides much better results than non-perceptual models such as HSV.