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Reality 4.27
Reality 4.27
  • Reality 4.27
    • What's New
    • Introduction to Reality
    • Reality Walkthrough
      • Reality Examples Project
      • Tracking Calibration and Fine Tuning
      • Real-Time Ray Tracing
      • Raw Input
      • Augmented Reality Virtual Studio
      • Green Screen Virtual Studio
      • Setting up Realtime Video I/O
      • Projection Cube
      • Cyclorama Setup
      • Reality Keyer and Fine Tuning
        • Keyer FOV Softness
    • Reality Editor Guide
      • How Reality Editor Works?
      • Exporting UE4 Actors to RealityHub API
        • ZDActor Component
        • Exporting Blueprint Functions
        • Texture Pins on ZDActors
        • Exporting Properties
          • Directly Readable Variable Types
          • Property Update Callbacks
            • OnChanged_Event Callback
            • OnLengthChanged_Event Callback
            • OnChanged_ Function Callback
            • OnLengthChanged_ Function Callback
      • Exporting Assets to Reality API
        • Exporting Actors
        • Exporting Custom Blueprint Node
        • Exporting Custom Material Node
        • Exporting Lens Calibration
        • Exporting Post Process Material
        • Exporting Projection Material
        • Exporting Static Mesh
        • Exporting Unreal Motion Graphics
        • Exporting Unreal Texture Assets
      • Reality Custom Material Nodes
        • Defining the Variables in Material Definition
        • Custom Material Node
      • Using UMG in Reality
        • How to Use UMG with Reality
        • UMG Animations
        • Texture Brush
        • Asset Brush
        • Exporting Custom Events in UMG to Reality API
      • Additional ZD Components
        • ZDPieChart
        • ZDText
      • Helpful Links
      • Reality Editor Settings
        • Enabling DX12 and Ray Tracing
        • Hardware Accelerated Video Decoding
        • Enabling HAP Codec
    • Reality Setup Application
      • Audio
        • Audio Delay Node
        • Virtual Set Audio
        • Audio Mixer
      • Bypass Post Process
      • Fill and Key
        • Fill and Key using Dual-link
        • Fill and Key using Quad-link
      • Crop Function
      • Level Sequencer
      • Color Matrix Node
      • Media Playback
      • Preset for H.264 in Adobe Media Encoder
      • HAP Video Codec
      • Flow Control
      • GPUDirect Technology
    • Installation and Configuration Guide
      • Hardware Platforms
        • Legacy HP Z4G4 Configuration
          • Fan and Front Card Kit
          • Certified Power Supply
          • Video I/O Card Installation
            • Mellanox ConnectX®-5 Card Installation
            • AJA Video I/O Card Installation
          • GPU installation
            • Certified GPUs
            • Connecting GPU to 1000 watts power supply
              • GPU RTX 6000 installation (8+6 pin)
            • Connecting GPU to 750 watts power supply
              • GPU RTX 6000 installation (8+6 pin) Needs 6 to 8 Pin Adapter
          • Installing RAM
          • HP Performance Advisor
      • Adding Reality User to Windows
      • Downloading Distributions
      • Installing Steps
        • Upgrading
        • Installation
      • Configuration Steps
        • NVIDIA Configuration
        • AJA Video Card Configuration
        • R Drive Mapping
        • Internet Options
      • Updating RealityEngine AMPERE
    • Licensing Guide
      • Hardware Licensing
    • Reality Tutorials and Examples
      • Reality Editor Tutorials
        • Open/Close Door
        • Exporting UE Actor to ZD API (a.k.a ZDActor)
        • Custom Blueprint Node Tutorials
          • Using Event Tick Functions and Properties
          • Adding Custom Blueprint Nodes
        • Redirection of the Reality Engine Content
        • Creating Dynamic Materials
        • Changing ZDText with Dynamic String
        • Activating Destructible Mesh
        • Reality Texture Input
        • Activating Fire During Runtime
        • Asset Migration to Another Project
        • Rotating Door by Using Function Parameters
        • Creating Custom Cyclorama
      • Nodegraph Tutorials
        • Portal Window Setup
          • Adding Clipping Plane
          • How to Position Videowall
          • Setting Portal Window and Calibration
          • Creating the Augmented Part
    • Appendices
      • A - Camera Tracking and Lens Calibration
        • Camera Tracking Information
        • Tracking Device, Physical Connections
        • Lens Calibration
      • B - Standard Unreal Engine Post Processing Pipeline
      • C - Reality Keyer
        • What is Image Based Keying?
        • Reality Keyer Pipeline
        • Physical Factors Affecting the Key
      • D - Viewing Videomask
      • E - CLASS setting for Broadcast Cameras
      • F - ZD Blueprint Node Pin Reference
      • G - Utilizing TRAXIS talentS FreeD Data
    • Knowledge Base
    • Known Issues and Limitations
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  1. Reality 4.27
  2. Appendices
  3. C - Reality Keyer

What is Image Based Keying?

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Last updated 2 years ago

Traditional chroma keyers select one RGB (HLS, YUV, etc..) value and create the key signal using that selected color. This means that, when using a traditional chroma keyer, your incoming image should have exactly the same RGB values on every pixel. In real-world, this is very unlikely to happen. Usually you will have some variance in your green screen image due to uneven lighting. In order to tolerate the variances in green screen color, chroma keyers have to increase the tolerance (thus clipping fine details like hair) or increase the softness (introduces wrong transparent areas in the key).

Image based keying tries to solve this problem using a clean plate. This clean plate should be captured after you set your lighting and camera setups. An image-based keyer would look for the changes between the clean plate and incoming video. This means that, we have individual key color setting for every pixel in our incoming image. So, we don’t need to add tolerance to clamp the uneven green values. As a result, we can extract fine details like hair, transparent object and contact shadows, even if the cyclorama is not perfectly uniform in terms of color. This capability of image based keying allows you to lit your subjects more freely. You can create shadows on the ground floor using physical lighting and use that keyed shadow in your final composite.

Reality Keyer with Moving Camera

Reality Keyer uses clean plate as the source key color for every pixel. This is the way we suggest to key trackless camera subjects. When the camera moves, we need to create the clean plate every frame. This is achieved using the CYCLORAMA node within Reality. CYCLORAMA node is used to define your physical cyclorama geometry. After your cyclorama is defined and aligned with your camera tracking systems, this node can be used to generate the clean plates and soft garbage mask for your green screen production. Basically, it is very similar to single frame clean plate capturing. After you set your lights and camera, capture a panorama of your cyclorama using the widest zoom level. The captured panorama is mapped on to the geometry and rendered every frame as a clean plate for the Reality Keyer’s clean plate input.