> For the complete documentation index, see [llms.txt](https://wiki.redmodding.org/redengine3-research/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.redmodding.org/redengine3-research/assets/shaders.md). # Shaders ## What are shaders? Every visual asset in REDengine 3 uses a specific shader, designated by REDengine as W2MG (.w2mg/Witcher 2 material graph) files. Even meshes "without a shader" are in-fact using a debug shader such as debug.w2mg. Shaders are the most basic expression of a surface, ranging from glass, skin, concrete, and steel. Each shader contains a combination of constant hidden-variables, and exposed variables for artists to tweak. For example, all skin exhibits some similar properties such as subsurface scattering so there is no reason to expose this; artists cannot use the skin shader without subsurface scattering. However skin color can vary dramatically, so these parameters are exposed to the artists using textures. Artists are able to create "instances" of shaders called [**Material Instances**](/redengine3-research/assets/shaders/materials.md) which contain localized variations of the textures and properties exposed by the base shader. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://wiki.redmodding.org/redengine3-research/assets/shaders.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.