mk_framework/assets/materials/sprite-gray.mtl

{
  "__type__": "cc.Material",
  "_name": "sprite-gray",
  "_objFlags": 0,
  "_native": "",
  "_effectAsset": {
    "__uuid__": "a81c05da-f587-40ac-94a2-3c2b6962e5fc"
  },
  "_techniqueIndex": 0,
  "_techniqueData": {
    "0": {
      "defines": {
        "USE_TEXTURE": true,
        "USE_GRAY": true
      },
      "props": {
        "grayLevel": 0
      }
    }
  }
}