# Shader Requirements
You may follow the [VRM MToon 1 Spec](https://github.com/vrm-c/vrm-specification/tree/master/specification/VRMC_materials_mtoon-1.0) and set up MToon 1 in Unity, or in Blender.
**Notes for Blender:**
### **Must use MToon1 or** [**GLTF Compatible Shader Models**](https://docs.blender.org/manual/en/latest/addons/import_export/scene_gltf2.html)**!**
If you you want to use the UV Transform feature, automatic outlines, or other VRM features, you must use MToon. However, gltf supported shaders (like principled BSDF) are also supported w/o VRM features.
* **DO NOT EDIT MTOON SETTINGS IN THE SHADER GRAPH**; changes won't export.
* Instead, adjust MToon in the "**VRM Material**" section of the material properties panel. NOT the “**Shader**” section.
**Only changes made here will be exported by the addon:**
|  | The face should be unlit, no need for custom normals or normal maps Please draw static shadows on the face The body, hair, and other accessories *can be* lit with custom normals, *or* unlit. Up to artist discretion. Most Unity features are supported 1:1 Transparency Render queue offset Shading shift GI Equalization Emission Rim Matcap *(Preview not correct in blender, check in VRM app like VRM Posing desktop)* Outlines *(only World Space Preview in Blender)* UV Animation *(Preview not correct in blender, check in VRM app like VRM Posing desktop)* |
| ---------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
If you’re using GLTF compatible shaders, double check requirements in [the documentation](https://docs.blender.org/manual/en/latest/addons/import_export/scene_gltf2.html). VRM is built on GLTF, so you can use shader models like Principled BSDF, Emission, and Background.
### **Outlines**
* **We use the MToon shader outline with a width mask where possible to reduce file size.**
* However, there are some rare occasions where a manual inverted hull needs to be made
* As an example: the transparent section of Hallway Chan’s hair needs a custom material set for the outline with a special render queue offset. This cannot be done with the basic MToon outline. So we needed to make an inverted hull with a separate outline material there.
* See section **circled in yellow** above in MToon panel
* **Only world space preview works inside blender**, use a VRM app like VRM Posing desktop to preview screen space
* After you select “Outline Width” mode, a geo nodes modifier will be added to the model for preview
* With the new viewport compositor, we may add a screen-space preview feature soon
* **Please take advantage of the Outline Width vertex mask to vary line width!**
* Thinner lines around the eyes and mouth is better.
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