Summary

The NVIDIA Material Definition Language (MDL) is a technology developed by NVIDIA to define physically-based materials for physically-based rendering solutions. It allows for the sharing of materials between different renderers, ensuring a consistent look across various rendering techniques. This article explores the main ideas behind MDL, its ecosystem, and how it facilitates the sharing of physically-based materials between renderers.

The Power of MDL: Unifying Physically-Based Materials Across Renderers

Physically-based rendering (PBR) has become a standard in the graphics industry, aiming to accurately represent real-world materials by using realistic shading and lighting models along with measured surface values. However, different rendering techniques can produce varying results, making it challenging to maintain a consistent look across different renderers. This is where the NVIDIA Material Definition Language (MDL) comes into play.

What is MDL?

MDL is a domain-specific programming language designed to define physically-based materials and lights for rendering. It serves as an industry standard for material exchange, ensuring that materials look consistent across different rendering techniques and engines.

The MDL Ecosystem

The MDL ecosystem is built around the idea of sharing physically-based materials between renderers. It includes:

  • MDL SDK: An open-source set of tools that enable the integration of physically-based materials into rendering applications. It provides a toolkit for material creation, compilation, and execution across various backends such as CUDA PTX, LLVM IR, HLSL, and GLSL.
  • Material Definition: MDL materials consist of two parts: a declarative material definition and procedural functions. The material definition is based on a robust material model, while the functions compute parameter values for the material model.
  • Compilation and Execution: MDL materials can be compiled into a compact, optimized representation and executed across different renderers, ensuring a consistent look.

Sharing Materials Across Renderers

One of the key benefits of MDL is its ability to share materials across different renderers without modifications. This is achieved through:

  • Consistent Material Appearance: MDL ensures that materials look consistent across different rendering techniques, such as path tracing, interactive ray tracing, and real-time rasterization.
  • No Scene Modifications: Switching between renderers does not require scene modifications, making it easier to maintain a consistent look across different rendering environments.

MDL in Practice

MDL has been integrated into various rendering applications and engines, including:

  • Iray Photoreal: A physically-based rendering solution that uses MDL to define materials.
  • Substance Designer: A texturing tool that supports MDL for creating physically-based materials.
  • OptiX: A scalable framework for building ray tracing-based applications that can use MDL materials.

Example Workflow

The MDL SDK provides an example workflow for material creation, which includes:

  • Material Definition: Creating a material definition using MDL.
  • Compilation: Compiling the material into a compact, optimized representation.
  • Execution: Executing the compiled material across different renderers.

Benefits of MDL

The use of MDL offers several benefits, including:

  • Consistency: Ensures a consistent look across different rendering techniques and engines.
  • Flexibility: Allows for the sharing of materials between different renderers without modifications.
  • Industry Standard: Serves as an industry standard for material exchange, making it easier to integrate physically-based materials into rendering applications.

Table: Key Features of MDL

Feature Description
Material Definition Defines physically-based materials using a declarative material model and procedural functions.
Compilation and Execution Compiles materials into a compact, optimized representation and executes them across different renderers.
Consistent Material Appearance Ensures a consistent look across different rendering techniques and engines.
No Scene Modifications Allows for switching between renderers without scene modifications.
Industry Standard Serves as an industry standard for material exchange.

Table: MDL SDK Components

Component Description
MDL Modules Packages materials and functions for re-use.
Internal Database Provides access to all material and function definitions.
Transactions and Call Graphs Creates, edits, and stores material instances and function calls.
Compiled Materials Compiles graphs into a compact, optimized representation.
Distilling and Texture Baking Maps or simplifies compiled MDL materials to more limited material models and bakes textures for optimal rendering performance.
Backends Provides code generation for various backends such as CUDA PTX, LLVM IR, HLSL, and GLSL.

Conclusion

The NVIDIA Material Definition Language (MDL) is a powerful tool for defining physically-based materials and sharing them across different renderers. Its ecosystem, which includes the MDL SDK and various rendering applications, ensures a consistent look across different rendering techniques and engines. By using MDL, developers can create high-quality, physically-based materials that can be used across a wide range of rendering environments, making it an essential tool for the graphics industry.