UniVRM/Assets/VRM/Runtime/IO/VRMMToonTextureImporter.cs

using System.Collections.Generic;
using UniGLTF;
using UnityEngine;
using VRMShaders;

namespace VRM
{
    public static class VRMMToonTextureImporter
    {
        public static IEnumerable<(SubAssetKey, TextureDescriptor)> EnumerateAllTextures(GltfParser parser, glTF_VRM_extensions vrm, int materialIdx)
        {
            var vrmMaterial = vrm.materialProperties[materialIdx];
            foreach (var kv in vrmMaterial.textureProperties)
            {
                if (TryGetTextureFromMaterialProperty(parser, vrm, materialIdx, kv.Key, out var texture))
                {
                    yield return texture;
                }
            }
        }

        public static bool TryGetTextureFromMaterialProperty(GltfParser parser, glTF_VRM_extensions vrm, int materialIdx, string textureKey, out (SubAssetKey, TextureDescriptor) texture)
        {
            var vrmMaterial = vrm.materialProperties[materialIdx];
            if (vrmMaterial.shader == MToon.Utils.ShaderName && vrmMaterial.textureProperties.TryGetValue(textureKey, out var textureIdx))
            {
                var (offset, scale) = (new Vector2(0, 0), new Vector2(1, 1));
                if (TryGetTextureOffsetAndScale(vrm, materialIdx, textureKey, out var os))
                {
                    offset = os.offset;
                    scale = os.scale;
                }

                switch (textureKey)
                {
                    case MToon.Utils.PropBumpMap:
                        texture = GltfTextureImporter.CreateNormal(parser, textureIdx, offset, scale);
                        break;
                    default:
                        texture = GltfTextureImporter.CreateSRGB(parser, textureIdx, offset, scale);
                        break;
                }
                return true;
            }

            texture = default;
            return false;
        }

        public static bool TryGetTextureOffsetAndScale(glTF_VRM_extensions vrm, int materialIdx, string unityTextureKey, out (Vector2 offset, Vector2 scale) os)
        {
            var vrmMaterial = vrm.materialProperties[materialIdx];

            if (vrmMaterial.vectorProperties.TryGetValue(unityTextureKey, out var vector))
            {
                os = (new Vector2(vector[0], vector[1]), new Vector2(vector[2], vector[3]));
                return true;
            }

            os = (new Vector2(0, 0), new Vector2(1, 1));
            return false;
        }
    }
}