matrix.js

import { Vertex } from "./vertex.js";
export class Matrix3 {
  constructor(values) {
    if (values.length !== 9) {
      throw new Error("Matrix3 must have 9 values.");
    }
    this.values = values;
  }

  multiply(other) {
    const result = new Array(9).fill(0);

    for (let row = 0; row < 3; row++) {
      for (let col = 0; col < 3; col++) {
        for (let i = 0; i < 3; i++) {
          result[row * 3 + col] +=
            this.values[row * 3 + i] * other.values[i * 3 + col];
        }
      }
    }

    return new Matrix3(result);
  }

  transform(vertex) {
    return new Vertex(
      vertex.x * this.values[0] +
        vertex.y * this.values[3] +
        vertex.z * this.values[6],
      vertex.x * this.values[1] +
        vertex.y * this.values[4] +
        vertex.z * this.values[7],
      vertex.x * this.values[2] +
        vertex.y * this.values[5] +
        vertex.z * this.values[8]
    );
  }
}