Open Shading Language (OSL) is a shading language developed by Sony Pictures Imageworks for use in its Arnold Renderer. It is also supported by the Cycles render engine in Blender (starting with Blender 2.65). OSL's surface and volume shaders define how surfaces or volumes scatter light in a way that allows for importance sampling; thus, it is well suited for physically-based renderers that support ray tracing and global illumination.