20 D04_H03_03 Adding HDRI Backdrop Light and Color Grading using LUTs in...

Session 20 Summary – Color Grading & LUTs in Unreal Engine

🔹 Understanding Gamma & Color Science

• Linear RGB: How camera sensors capture light — brightness is directly proportional to light intensity.

• sRGB: How human vision perceives light — more sensitive to shadows and midtones.

• Gamma Curve: Used to convert linear RGB to sRGB for realistic display on screens.

• 18% Gray Concept: Human eye perceives mid-gray at ~18% intensity, not 50%.

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🎨 Creating a D-Log Look in Unreal

• D-Log: A flat, low-contrast image format used for capturing max color detail (like in RAW photography).

• In Unreal:

  • Use Post Process Volume > Film settings.

  • Set Toe and Shoulder values to 0 to simulate a D-Log image.

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🖼️ HDRI Backdrop for Environment Lighting

• HDRI images used to simulate realistic environments (like city streets or forests).

• HDRI adds ambient light and reflections to the 3D scene, mimicking real-world locations.

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🧪 Color Grading Workflow with DaVinci Resolve

1. Export High-Resolution Screenshot from Unreal (via console or capture tools).

2. Open DaVinci Resolve, import:

   • Unreal scene screenshot

   • LUT reference image (RGB 16x1)

3. Apply color corrections using:

   • Curves (Toe, Slope, Shoulder)

   • Temperature, Tint, RGB channel tweaks

4. Transfer the color grade to the reference LUT image.

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📁 Generating and Importing the LUT

• Export the graded LUT image (PNG) from DaVinci.

• Import into Unreal Engine under a LUTs folder.

• Set Texture properties:

  • Mip Maps: Disable

  • Texture Group: Set to Color Lookup Table

• Save and close.

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🎥 Applying LUT in Unreal Engine

• In Post Process Volume, go to:

  • Misc > Color Grading LUT

  • Select the imported LUT texture.

• Repeat for all cameras (Rig1, Rig2, etc.).

• Ensure Toe and Shoulder are set to 0 for consistent D-Log base.

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✅ Key Outcomes of the Session

• Understood the theory of Gamma, Linear RGB, and sRGB.

• Applied D-Log look to Unreal shots using Film settings.

• Color graded in DaVinci Resolve using LUTs and curves.

• Imported custom .PNG LUT into Unreal and applied across all cameras