Color Correction lookup texture

Color Correction Lut (Lut stands for lookup texture) is an optimized way of performing color grading in a post effect. Instead of tweaking the individual color channels via curves as in Color Correction Curves, only a single texture is used to produce the corrected image. The lookup will be performed by using the original image color as a vector that is used to address the lookup texture.

Advantages include better performance and more professional workflow opportunities, where all color transforms can be defined in professional image manipulation software (such as Photoshop or Gimp) and thus a more precise result can be achieved.

As with the other image effects, you must have the Standard Assets Effects package installed before it becomes available.

Properties

Lookup texture requirements

The 2D texture representation is required to be laid out in a certain way that it represents an unwrapped volume texture (imagine an image sequence of “depth slices”).

The following image shows an example of such an unwrapped texture which effectively enhances image contrast. It should be included in the standard packages.

Texture importer requirements include enabling Read/Write support and disabling texture compression. Otherwise, unwanted image artifacts will likely occur.

Example workflow

Always keep the basic neutral lookup texture (lut) ready as this will be the basis for generating all other corrective lut’s.

• Take a screenshot of your game

• Import into a graphics editor (such as Photoshop) and apply color adjustments (such as contrast, brightness, color levels adjustments) until a satisfying result has been reached

• Perform the same steps to the neutral lut and save as a new lut

• Assign new lut to the effect and hit Convert & Apply

Hardware support

This effect requires a graphics card with 3D texture support:

• PC: Generally all GPUs, except some really old ones (that is, those made before year 2006).
• Mobile: Requires OpenGL ES 3 or Metal; 3D textures not available on OpenGL ES 2.
• Consoles: All consoles support this feature.

All image effects automatically disable themselves when they can not run on end-users graphics card.