isDoubleSided property
Whether this geometry should be drawn without back-face culling.
Material-driven passes (the color pass) read the cull mode from the material, but the material-less passes (the selection mask, depth prepass, shadow map) cull back faces by default. A geometry whose facing is not a reliable front/back (a camera-facing billboard, whose winding flips with the view) overrides this to true so those passes draw it from both sides instead of culling it away.
Implementation
@override
bool get isDoubleSided => true;