nanogl-gltf/lib/elements/Skin.js

gltf loader

import { mat4 } from 'gl-matrix';
import GltfTypes from '../types/GltfTypes';
const M4 = mat4.create();
/**
 * The Skin element contains the joints nodes and inverse bind matrices used to animate a mesh.
 */
export default class Skin {
    constructor() {
        this.gltftype = GltfTypes.SKIN;
    }
    /**
     * Parse the Skin data.
     *
     * Is async as it needs to wait for all the skeleton root and joints Nodes,
     * and the possible inverseBindMatrices Accessor to be created.
     * @param gltfLoader GLTFLoader to use
     * @param data Data to parse
     */
    async parse(gltfLoader, data) {
        const jointPromises = data.joints.map(idx => gltfLoader.getElement(GltfTypes.NODE, idx));
        this.joints = await Promise.all(jointPromises);
        this.inverseBindMatrices = this.joints.map(mat4.create);
        if (data.inverseBindMatrices !== undefined) {
            const ibmAccessor = await gltfLoader.getElement(GltfTypes.ACCESSOR, data.inverseBindMatrices);
            this.inverseBindMatrices.forEach((m, i) => ibmAccessor.getValue(m, i));
        }
        if (data.skeleton !== undefined) {
            this.skeletonRoot = await gltfLoader.getElement(GltfTypes.NODE, data.skeleton);
        }
    }
    /**
     * Compute the joints matrices, used to animate the skin.
     * @param skinnedNode Skinned node to compute the joints matrices for
     * @param jointMatrices Joints matrices to compute
     */
    computeJoints(skinnedNode, jointMatrices) {
        if (jointMatrices.length !== this.joints.length) {
            throw new Error("Skin.computeJoints(), jointMatrices size must match joints size");
        }
        mat4.invert(M4, skinnedNode._wmatrix);
        for (let i = 0; i < this.joints.length; i++) {
            const joint = this.joints[i];
            const ibm = this.inverseBindMatrices[i];
            const jointMatrix = jointMatrices[i];
            mat4.mul(jointMatrix, joint._wmatrix, ibm);
            mat4.mul(jointMatrix, M4, jointMatrix);
        }
    }
}