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OpenUSD Exchange Samples: createLights

This sample demonstrates how to open/create a stage with key metadata and create OpenUSD lights using the OpenUSD Exchange SDK.

  • A UsdLuxRectLight describes light emitted from one side of a rectangle.
  • A UsdLuxDomeLight describes light emitted inward from a distant external environment, such as a sky or imaged base light.

USD Modules

The Gf, Sdf, Usd, and UsdLux modules are used.

OpenUSD Exchange SDK functions

  • createColorAttr()
  • createStage()
  • defineDomeLight()
  • defineRectLight()
  • getValidChildNames()
  • saveStage()
  • setLocalTransform()

Languages

This sample is implemented in both C++ and Python. To run:

  • [./]run.[bat, sh] createLights
  • [./]python.[bat, sh] source/createLights/createLights.py

Hardcoded items

  • If a stage is created, it will have a default prim named "World", Y-up axis, 1 cm linear units
  • The rect light named "rectLight" is created with these properties:
    • 100x33 cm
    • 5,000 intensity
      • Note: this intensity is fairly high, the intention is to make a very visible blue light. Also note that the default material in Omniverse Kit is very reflective so it's difficult to see the light on the createStage and createMesh geometry outside of the light's reflection.
      • Different DCC applications and renders will treat light intensity, exposure, etc. differently. When authoring lights, the target renderer and application should be considered.
    • 300 cm high, rotated to point down
  • The dome light named "domeLight" is created with these properties:
    • 0.3 intensity
      • USDView likes a much lower intensity (0.3) than Omniverse Kit/RTX (1000). An intensity of 1000 washes out everything in USDView.
    • an HDRI texture is copied to the stage folder and set as the light texture file
    • to render properly in Omniverse Kit/RTX, apply a rotation -90 on the X axis to point -Z down

Command Line Arguments

Usage:
  createLights [OPTION...]

  -a, --usda          Output a text stage rather than binary
  -h, --help          Print usage
  -p, --path arg      Alternate destination stage path (default: c:/Users/username/AppData/Local/Temp/usdex/sample.usdc)