When real-time 3D characters and assets are drawn on the UI (RawImage) via a render texture (RenderTexture), the color tone does not match the original asset, resulting in dark, dirty colors or blurred white. This is a very common problem that occurs due to a color space interpretation error. In this article, we will explain this ``difference between linear and gamma'' in an easy-to-understand manner using the analogy of ``double dimming while wearing sunglasses,'' and present settings and implementation procedures to perfectly synchronize color tones.

1. Understanding with an analogy: ``double dimming while wearing sunglasses''

To intuitively understand this color space mismatch, let's consider ``finishing a painting done while wearing sunglasses'' as an example.

Suppose you are painting a very beautiful painting (3D model) outdoors in bright light. At that time, you looked at the canvas while wearing ``strong sunglasses (gamma correction)'' and finished by adjusting the colors (lighting using linear calculations) to get just the right brightness. The picture is 'perfectly toned' through your sunglasses.

Next, in order to display this painting in a dark gallery (UI screen), put it in a special case (RenderTexture) for transportation. However, the transportation staff (who set up Unity) mistakenly thought that the picture inside the case was raw data that had not yet been shaded from the sun, and arbitrarily corrected the brightness of the picture inside the case numerically (an incorrect linear conversion). Furthermore, gallery exhibition staff (UI shaders) also look at the paintings while wearing ``sunglasses (decoding processing)'' and adjust the brightness of the exhibition position. As a result, the color balance of the original painting is doubly distorted, and the moment an ordinary viewer takes off his sunglasses and visits the gallery to view the painting, a color collapse occurs in whichthe finished painting appears extremely dark and sunken (or overexposed due to too much light).

This is the mechanism behind the colorspace mismatch bug in RenderTexture. Unity, which operates in Linear space, automatically makes corrections when drawing and displaying by marking whether the texture is sRGB (gamma) or linear. If the RenderTexture settings (marks) are incorrect, this correction may be applied twice (double exponentiation and darkening) or may not be applied (overexposure).

2. Solution A: Enabling the 'sRGB' setting for the RenderTexture asset

If you have created a RenderTexture asset (`.renderTexture` file) in your project folder and are using it by directly assigning it to a RawImage, modify the marks correctly from the Inspector settings.

Setup steps:

  1. Select the appropriate RenderTexture asset from the project window.
  2. Check the inspector window.
  3. In the ``Color Format'' settings, explicitly select the format with ``sRGB'' in the name (e.g. `R8G8B8A8_SRGB`).

As a result, Unity's drawing engine correctly recognizes this RenderTexture as ``color data in gamma space (sRGB)'', and when the UI system samples it and renders it on the screen, it automatically performs the correct linear conversion, which instantly eliminates the darkening bug.

3. Solution B: Dynamically enable sRGB with a C# script

If you want to dynamically create a RenderTexture using a C# script, explicitly set the `sRGB` property to `true` in the `RenderTextureDescriptor` to perform the allocation. 

using UnityEngine;
using UnityEngine.UI;

public class CharacterPreviewColorFix : MonoBehaviour
{
    public Camera subCamera;
    public RawImage rawImage;
    private RenderTexture targetRt;

    void Start()
    {
        InitializeRenderTexture();
    }

    void InitializeRenderTexture()
    {
        // 1. Create a descriptor with resolution and precision
 RenderTextureDescriptor desc = new RenderTextureDescriptor(1024, 1024, RenderTextureFormat.ARGB32, 24);
 
 // 2. ★Super important: Explicitly set sRGB setting to true (hook automatic gamma correction)
 desc.sRGB = true;
 desc.useMipMap = false;
 desc.autoGenerateMips = false;

 // 3. Generate texture
 targetRt = new RenderTexture(desc);
 targetRt.filterMode = FilterMode.Bilinear;
 targetRt.Create();

 // Set camera target and UI reference
 subCamera.targetTexture = targetRt;
 rawImage.texture = targetRt;
 }

 void OnDestroy()
 {
 if (targetRt != null)
 {
 targetRt.Release();
 Destroy(targetRt);
 }
 }
}

The buffer dynamically allocated through this script will automatically encode and save the 3D color data calculated in linear space to sRGB format. This completely prevents double conversions that occur when drawing RawImages in uGUI, and allows previews to be displayed on the UI with 100% the same color balance as the original assets.