JsMaterialXPhysicallyBased.js

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let MTLX_NODE_NAME_ATTRIBUTE = 'nodename';
 
class JsPhysicallyBasedMaterialLoader {
    url = '';
    headers = {};
    materials = null;
    materialNames = [];
    mxMaterialNames = [];
    mx = null;
    doc = null;
    stdlib = null;
    remapMap = {};
 
    constructor(mtlx_module = null, mtlx_stdlib = null) 
    {
        this.url = 'https://api.physicallybased.info/materials';
        this.headers = { 'Accept': 'application/json' };
 
        this.materials = null;
        this.materialNames = [];
 
        this.mxMaterialNames = [];
        this.mx = null;
        if (mtlx_module) {
            this.mx = mtlx_module;
        }
        this.stdlib = null;
        if (mtlx_stdlib) {
            this.stdlib = mtlx_stdlib;
        }
        this.doc = null;
 
        this.initializeInputRemapping();
    }
 
    getJSON() 
    {
        return this.materials
    }
 
    getJSONMaterialNames()
    {
        return this.materialNames
    }
 
    getMaterialXDocument() 
    {
        return this.doc;
    }
 
    validateDocument() 
    {
        if (this.doc) {
            let errors = {}
            let errorString = ''
            var valid = this.doc.validate(errors);
            if (!valid) {
                errorString = errors.message;
            }
            return [valid, errorString]
        }
        return [false, 'No MaterialX document'];
    }
 
    getInputRemapping(shadingModel) 
    {
        if (shadingModel in this.remapMap) {
            return this.remapMap[shadingModel];
        }
        return {};
    }
 
    initializeInputRemapping() 
    {
        // Remap keys for Autodesk Standard Surface shader. How to verify this?
        const standard_surface_remapKeys = {
            'color': 'base_color',
            'specularColor': 'specular_color',
            'roughness': 'specular_roughness',
            //'metalness': 'metalness',
            'ior': 'specular_IOR',
            //'transmission': 'transmission',
            'transmission_color': 'transmission_color',
            'thinFilmIor': 'thin_film_IOR',
            'thinFilmThickness': 'thin_film_thickness',
            'transmissionDispersion': 'transmission_dispersion',
        }
        // Remap keys for OpenPBR shading model.
        const openpbr_remapKeys = {
            'color': 'base_color',
            'specularColor': 'specular_color',
            'roughness': 'specular_roughness', // 'base_diffuse_roughness',
            'metalness': 'base_metalness',
            'ior': 'specular_ior',
            'transmission': 'transmission_weight',
            'transmission_color': 'transmission_color',
            'subsurfaceRadius': 'subsurface_radius',
            'thinFilmIor': 'thin_film_ior',
            'thinFilmThickness': 'thin_film_thickness',
            'transmissionDispersion': 'transmission_dispersion_scale',
        }
        // Remap keys for Khronos glTF shading model.
        const gltf_remapKeys = {
            'color': 'base_color',
            'specularColor': 'specular_color',
            'roughness': 'roughness',
            'metalness': 'metallic',
            'transmission_color': 'attenuation_color',
            //'ior': 'ior',
            //'transmission': 'transmission',
        }
 
        this.remapMap = {}
        this.remapMap['standard_surface'] = standard_surface_remapKeys;
        this.remapMap['gltf_pbr'] = gltf_remapKeys;
        this.remapMap['open_pbr_surface'] = openpbr_remapKeys;
    }
 
    loadMaterialX() 
    {
        return new Promise((resolve, reject) => {
            MaterialX().then((mtlx) => {
                this.mx = mtlx;
                resolve();
            }).catch((error) => {
                reject(error);
            });
        });
    }
 
    async getPhysicallyBasedMaterials() 
    {
        try {
            this.materials = null
            this.materialNames = [];
 
            const response = await fetch(this.url, {
                method: 'GET',
                headers: this.headers
            });
 
            if (!response.ok) {
                throw new Error('Network response was not ok ' + response.statusText);
            }
 
            this.materials = await response.json();
            for (let i = 0; i < this.materials.length; i++) {
                this.materialNames.push(this.materials[i]['name']);
            }
            return this.materials;
        } catch (error) {
            console.error('There has been a problem with your fetch operation:', error);
        }
 
        return null;
    }
 
    loadStandardLibraries() 
    {
        if (!this.mx) {
            // Call the asynchronous function and then perform additional logic
            this.loadMaterialX().then(() => {
 
                this.esslgenerator = new this.mx.EsslShaderGenerator();
                this.esslgenContext = new this.mx.GenContext(this.esslgenerator);
                this.stdlib = this.mx.loadStandardLibraries(this.esslgenContext);
                let children = this.stdlib.getChildren();
                for (let i = 0; i < children.length; i++) {
                    let child = children[i];
                    child.setSourceUri('STDLIB_ELEMENT');
                }
 
                console.log("MaterialX is loaded");
            }).catch((error) => {
                console.error("Error loading MaterialX:", error);
            });
        }
    }
 
    skipLibraryElement(element) 
    {
        return !elem.hasSourceUri()
    }
 
    getMaterialXString() 
    {
        if (!this.doc) {
            console.error('No MaterialX document to convert');
            return '';
        }
 
        // Create write options
        const writeOptions = new this.mx.XmlWriteOptions();
        writeOptions.writeXIncludeEnable = false;
        //writeOptions.writeXIncludes = false;
        writeOptions.elementPredicate = this.skipLibraryElement;
 
        // Convert the MaterialX document to a string
        const mtlx = this.mx.writeToXmlString(this.doc, writeOptions);
        return mtlx;
    }
 
    addComment(doc, commentString) 
    {
        let comment = doc.addChildOfCategory('comment')
        comment.setDocString(commentString)
    }
 
 
    convertToMaterialX(shaderCategory, addAllInputs = false, materialNames = [], remapKeys = {}, shaderPreFix = '') 
    {
        if (!this.mx) {
            console.error('MaterialX module is not loaded');
            return false;
        }
 
        if (!this.materials) {
            console.warn('No Physically Based Materials to convert');
            return false;
        }
 
        if (remapKeys.length == 0) {
            remapKeys = this.getInputRemapping(shaderCategory);
        }
 
        // Create a dummy doc with the surface shader with all inputs
        // as reference
        let refDoc = this.mx.createDocument();
        refDoc.importLibrary(this.stdlib);
        const refNode = refDoc.addNode(shaderCategory, 'refShader', this.mx.SURFACE_SHADER_TYPE_STRING);
        //refNode.addInputsFromNodeDef() -- This is missing from the JS API.
        this.doc = this.mx.createDocument();
 
        // Add header comments
        this.addComment(this.doc, 'Physically Based Materials from https://api.physicallybased.info ');
        this.addComment(this.doc, '  Processed via API and converted to MaterialX ');
        this.addComment(this.doc, '  Target Shading Model: ' + shaderCategory);
        this.addComment(this.doc, '  Utility Author: Bernard Kwok. kwokcb@gmail.com ');
 
        // Add properties to the material
        for (let i = 0; i < this.materials.length; i++) {
            const mat = this.materials[i];
            let matName = mat['name'];
 
            // Filter by material name(s)
            if (materialNames.length > 0 && !materialNames.includes(matName)) {
                // Skip material
                console.log('Skipping material:', matName);
                continue;
            }
 
 
            if (shaderPreFix.length > 0) {
                matName = shaderPreFix + '_' + matName;
            }
 
            const shaderName = this.doc.createValidChildName('SPB_' + matName);
            this.addComment(this.doc, ' Generated shader: ' + shaderName + ' ');
            const shaderNode = this.doc.addNode(shaderCategory, shaderName, this.mx.SURFACE_SHADER_TYPE_STRING);
            let docString = mat['description'];
            const refString = mat['reference'];
            if (refString.length > 0) {
                if (docString.length > 0) {
                    docString += '. ';
                }
                docString += 'Reference: ' + refString[0];
            }
            if (docString.length > 0) {
                shaderNode.setDocString(docString);
            }
 
            // Create a new material
            const materialName = this.doc.createValidChildName('MPB_' + matName);
            this.addComment(this.doc, ' Generated material: ' + materialName + ' ');
            const materialNode = this.doc.addNode(this.mx.SURFACE_MATERIAL_NODE_STRING, materialName, this.mx.MATERIAL_TYPE_STRING);
            const shaderInput = materialNode.addInput(this.mx.SURFACE_SHADER_TYPE_STRING, this.mx.SURFACE_SHADER_TYPE_STRING);
            shaderInput.setAttribute(MTLX_NODE_NAME_ATTRIBUTE, shaderNode.getName());
 
            // Warning this is a bit bespoke for remapping keys
            // to Autodesk Standard Surface shader inputs
            const skipKeys = ['name', "density", "category", "description", "sources", "tags", "reference"];
 
            let metallness = null;
            let roughness = null;
            let transmission_color = null;
            let transmission = null;
            Object.entries(mat).forEach(([key, value]) => {
 
                if (!skipKeys.includes(key)) {
 
                    if (key == 'metalness') {
                        metallness = value;
                        //console.log('Metalness:', metallness);
                    }
                    if (key == 'roughness') {
                        roughness = value;
                        //console.log('Roughness:', roughness);
                    }
                    if (key == 'transmission') {
                        transmission = value;
                        //console.log('Transmission:', transmission);
                    }
                    if (key == 'color') {
                        transmission_color = value;
                        //console.log('Color:', color);
                    }    
 
                    if (remapKeys[key]) {
                        key = remapKeys[key];
                    }
 
                    let refInput = refNode.getInput(key);
                    if (!refInput)
                        refInput = refNode.addInputFromNodeDef(key);
                    if (refInput) {
                        const input = shaderNode.addInput(key);
                        input.copyContentFrom(refInput);
                        if (input) {
                            // Convert number vector to string
                            if (Array.isArray(value)) {
                                value = value.join(',');
                            }
                            // Convert number to string
                            else if (typeof value === 'number') {
                                value = value.toString();
                            }
                            // Note: This API has side-effects as the
                            // type is set to "string" when the value is set. Thus
                            // we must explicitly set the type here.
                            input.setValueString(value, refInput.getType());
                        }
                    }
                    else {
                        //console.log('>>> Cannot create input:', key)
                    }
                }
            });
 
            if (transmission !== null && metallness !== null && roughness !== null && transmission_color !== null) 
            {
                if (metallness == 0 && roughness == 0) 
                {
                    if (remapKeys['transmission_color']) {
                        let inputName = remapKeys['transmission_color'];
                        let input = shaderNode.addInput(inputName);
                        if (input) {
                            let value = transmission_color.join(',');
                            console.log(`Add "${inputName}": "${value}"`);
                            input.setValueString(value, 'color3');
                        }
                    }
                }
            };                
        }
        return true;
    }
 
}