www.nvidia.com/en-us/design-visualization/technologies/material-definition-language/
THE NVIDIA MATERIAL DEFINITION LANGUAGE (MDL) gives you the freedom to share physically based materials and lights between supporting applications.
For example, create an MDL material in an application like Allegorithmic Substance Designer, save it to your library, then use it in NVIDIA® Iray® or Chaos Group’s V-Ray, or any other supporting application.
Unlike a shading language that produces programs for a particular renderer, MDL materials define the behavior of light at a high level. Different renderers and tools interpret the light behavior and create the best possible image.
