Material-related fixes and additions in UniVRM-0.44.

Introduction of UniGLTF / UniUnlit shader

UniVRM-0.43 was capable of importing / exporting the following Unlit shaders:

• Unlit/Color
• Unlit/Texture, VRM/UnlitTexture
• Unlit/Transparent, VRM/UnlitTransparent
• Unlit/Transparent Coutout, VRM/UnlitCutout
• VRM/UnlitTransparentZWrite(not compatible with GLTF)

The following materials that are set with GLTF were not functional:

• doubleSided
• the multiplication of color and texture
• transparent with color
• vertex color

Hence, we introduced the GLTF-compatible Unlit shader UniGLTF / UnLit:

• RenderType: Opaque, Cutout, Transparent, TransparentZWrite(VRM extension)
• CullMode: Off(doubleSided=True), Back(doublueSided=False), Front(VRM extension)
• VertexColorBlend: None, Multiply

Improvement of texture conversion of Standard shaders

The processing of textures other than Standard shader color has been improved.

• Normal map correction: Since it is also applied to MToon, we put the details in the next section
• Metallic, Roughnes, OcclusionMap conversion
  • RGBA channel recombination
  • Inversion of Roughness and Smoothness values
  • sRGB’s and Linear’s correspondence
  • Conversion with Importer, reverse conversion with Exporter

Correction of normal map import / export

The texture of Standard and MToon. Parse material’s property name according to _BumpMap.

• EditorImport: TextureImporterType.NormalMap
• RuntimeImport: Normal texture’s Pack
• Export: Normal texture’s Unpack
• sRGB’s and Linear’s correspondence
• Tangent’s correspondence