CS考试辅导 import { loadExternalFile } from ‘./js/utils/utils.js’

import { loadExternalFile } from ‘./js/utils/utils.js’

* A class to load OBJ files from disk
class OBJLoader {

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* Constructs the loader
* @param {String} filename The full path to the model OBJ file on disk
constructor(filename) {
this.filename = filename

* Loads the file from disk and parses the geometry
* @returns {[Array, Array]} A tuple / list containing 1) the list of vertices and 2) the list of triangle indices
throw ‘”OBJLoader.load” not implemented’

// Load the file’s contents
let contents = loadExternalFile(this.filename)

// Create lists for vertices and indices
let vertices = []
let indices = []

// TODO: STEP 1
// Parse the file’s contents
// You can loop through the file line-by-line by splitting the string at line breaks
// contentx.split(‘\n’)

// TODO: STEP 2
// Process (or skip) each line based on its content and call the parsing functions to parse an entry
// For vertices call OBJLoader.parseVertex
// For faces call OBJLoader.parseFace

// TODO: STEP 3
// Vertex coordinates can be arbitrarily large or small
// We want to normalize the vertex coordinates to fit within our [-1.0, 1.0]^3 box from the previous assignment
// As a pre-processing step and to avoid complicated scaling transformations in the main app we perform normalization here
// Determine the max and min extent of all the vertex coordinates and normalize each entry based on this finding

// TODO: HINT
// Look up the JavaScript functions String.split, parseFloat, and parseInt
// You will need thim in your parsing functions

// Return the tuple
return [ vertices, indices ]

* Parses a single OBJ vertex entry given as a string
* Call this function from OBJLoader.load()
* @param {String} vertex_string String containing the vertex entry ‘v {x} {y} {z}’
* @returns {Array} A list containing the x, y, z coordinates of the vertex
parseVertex(vertex_string)
throw ‘”OBJLoader.parseVertex” not implemented’

// TODO: Process the entry and parse numbers to float

* Parses a single OBJ face entry given as a string
* Face entries can refer to 3 or 4 elements making them triangle or quad faces
* WebGL only supports triangle drawing, so we need to triangulate the entry if we find 4 indices
* This is done using OBJLoader.triangulateFace()
* Each index entry can have up to three components separated by ‘/’
* You need to grad the first component. The other ones are for textures and normals which will be treated later
* Make sure to account for this fact.
* Call this function from OBJLoader.load()
* @param {String} face_string String containing the face entry ‘f {v0}/{vt0}/{vn0} {v1}/{vt1}/{vn1} {v2}/{vt2}/{vn2} ({v3}/{vt3}/{vn3})’
* @returns {Array} A list containing three indices defining a triangle
parseFace(face_string)
throw ‘”OBJLoader.parseFace” not implemented’

// TODO: Process the entry and parse numbers to ints
// TODO: Don’t forget to handle triangulation if quads are given

* Triangulates a face entry given as a list of 4 indices
* Use these 4 indices to create indices for two separate triangles that share a side (2 vertices)
* Return a new index list containing the triangulated indices
* @param {Array} face The quad indices with 4 entries
* @returns {Array} The newly created list containing triangulated indices
triangulateFace(face)
throw ‘”OBJLoader.triangulateFace” not implemented’

// TODO: Triangulate the face indices

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