UniVRM/Assets/VRM10/Runtime/IO/MaterialAdapter.cs

using VrmLib;
using System.Collections.Generic;
using System.Numerics;
using UniJSON;
using UniGLTF;
using System;

namespace UniVRM10
{
    public static class MaterialAdapter
    {
        public static Material FromGltf(this glTFMaterial x, List<Texture> textures)
        {
            if (UniGLTF.Extensions.VRMC_materials_mtoon.GltfDeserializer.TryGet(x.extensions,
                out UniGLTF.Extensions.VRMC_materials_mtoon.VRMC_materials_mtoon mtoon))
            {
                // mtoon
                return MToonAdapter.MToonFromGltf(x, textures, mtoon);
            }

            if (glTF_KHR_materials_unlit.IsEnable(x))
            {
                // unlit                
                return UnlitFromGltf(x, textures);
            }

            // PBR
            return PBRFromGltf(x, textures);
        }

        public static void LoadCommonParams(this Material self, glTFMaterial material, List<Texture> textures)
        {
            var pbr = material.pbrMetallicRoughness;
            if (pbr.baseColorFactor != null)
            {
                self.BaseColorFactor = LinearColor.FromLiner(pbr.baseColorFactor);
            }
            var baseColorTexture = pbr.baseColorTexture;
            if (baseColorTexture != null && baseColorTexture.index.TryGetValidIndex(textures.Count, out int index))
            {
                self.BaseColorTexture = new TextureInfo(textures[index]);
            }

            self.AlphaMode = EnumUtil.Parse<VrmLib.AlphaModeType>(material.alphaMode);
            self.AlphaCutoff = material.alphaCutoff;
            self.DoubleSided = material.doubleSided;
        }

        public static PBRMaterial PBRFromGltf(glTFMaterial material, List<Texture> textures)
        {
            var self = new PBRMaterial(material.name);

            self.LoadCommonParams(material, textures);

            //
            // pbr
            //
            var pbr = material.pbrMetallicRoughness;

            // metallic roughness
            self.MetallicFactor = pbr.metallicFactor;
            self.RoughnessFactor = pbr.roughnessFactor;
            var metallicRoughnessTexture = pbr.metallicRoughnessTexture;
            if (metallicRoughnessTexture != null
            && metallicRoughnessTexture.index.TryGetValidIndex(textures.Count, out int metallicRoughnessTextureIndex))
            {
                self.MetallicRoughnessTexture = textures[metallicRoughnessTextureIndex];
            }
            //
            // emissive
            //
            if (material.emissiveFactor != null)
            {
                self.EmissiveFactor = new Vector3(
                    material.emissiveFactor[0],
                    material.emissiveFactor[1],
                    material.emissiveFactor[2]);
            }
            var emissiveTexture = material.emissiveTexture;
            if (emissiveTexture != null
            && emissiveTexture.index.TryGetValidIndex(textures.Count, out int emissiveTextureIndex))
            {
                self.EmissiveTexture = textures[emissiveTextureIndex];
            }
            //
            // normal
            //
            var normalTexture = material.normalTexture;
            if (normalTexture != null
            && normalTexture.index.TryGetValidIndex(textures.Count, out int normalTextureIndex))
            {
                self.NormalTexture = textures[normalTextureIndex];
            }
            //
            // occlusion
            //
            var occlusionTexture = material.occlusionTexture;
            if (occlusionTexture != null
            && occlusionTexture.index.TryGetValidIndex(textures.Count, out int occlusionTextureIndex))
            {
                self.OcclusionTexture = textures[occlusionTextureIndex];
            }

            return self;
        }

        public static UnlitMaterial UnlitFromGltf(glTFMaterial material, List<Texture> textures)
        {
            var unlit = new UnlitMaterial(material.name);
            unlit.LoadCommonParams(material, textures);
            return unlit;
        }

        static string CastAlphaMode(VrmLib.AlphaModeType alphaMode)
        {
            if (alphaMode == AlphaModeType.BLEND_ZWRITE)
            {
                return "BLEND";
            }
            return alphaMode.ToString();
        }

        static glTFMaterial ToGltf(this VrmLib.Material src, List<Texture> textures)
        {
            var material = new glTFMaterial
            {
                name = src.Name,
                pbrMetallicRoughness = new glTFPbrMetallicRoughness
                {
                    baseColorFactor = src.BaseColorFactor.ToFloat4(),
                },
                alphaMode = CastAlphaMode(src.AlphaMode),
                alphaCutoff = src.AlphaCutoff,
                doubleSided = src.DoubleSided,
            };
            if (src.BaseColorTexture != null)
            {
                material.pbrMetallicRoughness.baseColorTexture = new glTFMaterialBaseColorTextureInfo
                {
                    index = textures.IndexOfNullable(src.BaseColorTexture.Texture).Value,
                };
            }
            return material;
        }

        public static glTFMaterial PBRToGltf(this PBRMaterial pbr, List<Texture> textures)
        {
            var material = pbr.ToGltf(textures);

            // MetallicRoughness
            material.pbrMetallicRoughness.baseColorFactor = pbr.BaseColorFactor.ToFloat4();
            if (pbr.BaseColorTexture != null)
            {
                material.pbrMetallicRoughness.baseColorTexture = new glTFMaterialBaseColorTextureInfo
                {
                    index = textures.IndexOfNullable(pbr.BaseColorTexture.Texture).Value,
                };
            }
            material.pbrMetallicRoughness.metallicFactor = pbr.MetallicFactor;
            material.pbrMetallicRoughness.roughnessFactor = pbr.RoughnessFactor;
            if (pbr.MetallicRoughnessTexture != null)
            {
                material.pbrMetallicRoughness.metallicRoughnessTexture = new glTFMaterialMetallicRoughnessTextureInfo
                {
                    index = textures.IndexOfNullable(pbr.MetallicRoughnessTexture).Value,
                };
            }

            // Normal
            if (pbr.NormalTexture != null)
            {
                material.normalTexture = new glTFMaterialNormalTextureInfo
                {
                    index = textures.IndexOfNullable(pbr.NormalTexture).Value,
                    scale = pbr.NormalTextureScale
                };
            }

            // Occlusion
            if (pbr.OcclusionTexture != null)
            {
                material.occlusionTexture = new glTFMaterialOcclusionTextureInfo
                {
                    index = textures.IndexOfNullable(pbr.OcclusionTexture).Value,
                    strength = pbr.OcclusionTextureStrength,
                };
            }

            // Emissive
            if (pbr.EmissiveTexture != null)
            {
                material.emissiveTexture = new glTFMaterialEmissiveTextureInfo
                {
                    index = textures.IndexOfNullable(pbr.EmissiveTexture).Value,
                };
            }
            material.emissiveFactor = pbr.EmissiveFactor.ToFloat3();

            // AlphaMode
            material.alphaMode = CastAlphaMode(pbr.AlphaMode);

            // AlphaCutoff
            material.alphaCutoff = pbr.AlphaCutoff;

            // DoubleSided
            material.doubleSided = pbr.DoubleSided;

            return material;
        }

        public static glTFMaterial UnlitToGltf(this UnlitMaterial unlit, List<Texture> textures)
        {
            var material = unlit.ToGltf(textures);

            if (!(material.extensions is glTFExtensionExport extensions))
            {
                extensions = new glTFExtensionExport();
                material.extensions = extensions;
            }
            extensions.Add(
                glTF_KHR_materials_unlit.ExtensionName,
                new ArraySegment<byte>(glTF_KHR_materials_unlit.Raw));

            material.pbrMetallicRoughness.roughnessFactor = 0.9f;
            material.pbrMetallicRoughness.metallicFactor = 0.0f;

            return material;
        }
    }
}