playcanvas/build/playcanvas.prf/src/scene/geometry/box-geometry.js

PlayCanvas WebGL game engine

import { Vec3 } from '../../core/math/vec3.js';
import { calculateTangents } from './geometry-utils.js';
import { Geometry } from './geometry.js';

const primitiveUv1Padding = 4.0 / 64;
const primitiveUv1PaddingScale = 1.0 - primitiveUv1Padding * 2;
class BoxGeometry extends Geometry {
		constructor(opts = {}){
				super();
				const he = opts.halfExtents ?? new Vec3(0.5, 0.5, 0.5);
				const ws = opts.widthSegments ?? 1;
				const ls = opts.lengthSegments ?? 1;
				const hs = opts.heightSegments ?? 1;
				const yOffset = opts.yOffset ?? 0;
				const minY = -he.y + yOffset;
				const maxY = he.y + yOffset;
				const corners = [
						new Vec3(-he.x, minY, he.z),
						new Vec3(he.x, minY, he.z),
						new Vec3(he.x, maxY, he.z),
						new Vec3(-he.x, maxY, he.z),
						new Vec3(he.x, minY, -he.z),
						new Vec3(-he.x, minY, -he.z),
						new Vec3(-he.x, maxY, -he.z),
						new Vec3(he.x, maxY, -he.z)
				];
				const faceAxes = [
						[
								0,
								1,
								3
						],
						[
								4,
								5,
								7
						],
						[
								3,
								2,
								6
						],
						[
								1,
								0,
								4
						],
						[
								1,
								4,
								2
						],
						[
								5,
								0,
								6
						]
				];
				const faceNormals = [
						[
								0,
								0,
								1
						],
						[
								0,
								0,
								-1
						],
						[
								0,
								1,
								0
						],
						[
								0,
								-1,
								0
						],
						[
								1,
								0,
								0
						],
						[
								-1,
								0,
								0
						]
				];
				const sides = {
						FRONT: 0,
						BACK: 1,
						TOP: 2,
						BOTTOM: 3,
						RIGHT: 4,
						LEFT: 5
				};
				const positions = [];
				const normals = [];
				const uvs = [];
				const indices = [];
				let vcounter = 0;
				const generateFace = (side, uSegments, vSegments)=>{
						const temp1 = new Vec3();
						const temp2 = new Vec3();
						const temp3 = new Vec3();
						const r = new Vec3();
						for(let i = 0; i <= uSegments; i++){
								for(let j = 0; j <= vSegments; j++){
										temp1.lerp(corners[faceAxes[side][0]], corners[faceAxes[side][1]], i / uSegments);
										temp2.lerp(corners[faceAxes[side][0]], corners[faceAxes[side][2]], j / vSegments);
										temp3.sub2(temp2, corners[faceAxes[side][0]]);
										r.add2(temp1, temp3);
										let u = i / uSegments;
										let v = j / vSegments;
										positions.push(r.x, r.y, r.z);
										normals.push(faceNormals[side][0], faceNormals[side][1], faceNormals[side][2]);
										uvs.push(u, 1 - v);
										u = u * primitiveUv1PaddingScale + primitiveUv1Padding;
										v = v * primitiveUv1PaddingScale + primitiveUv1Padding;
										u /= 3;
										v /= 3;
										u += side % 3 / 3;
										v += Math.floor(side / 3) / 3;
										if (i < uSegments && j < vSegments) {
												indices.push(vcounter + vSegments + 1, vcounter + 1, vcounter);
												indices.push(vcounter + vSegments + 1, vcounter + vSegments + 2, vcounter + 1);
										}
										vcounter++;
								}
						}
				};
				generateFace(sides.FRONT, ws, hs);
				generateFace(sides.BACK, ws, hs);
				generateFace(sides.TOP, ws, ls);
				generateFace(sides.BOTTOM, ws, ls);
				generateFace(sides.RIGHT, ls, hs);
				generateFace(sides.LEFT, ls, hs);
				this.positions = positions;
				this.normals = normals;
				this.uvs = uvs;
				this.uvs1 = uvs;
				this.indices = indices;
				if (opts.calculateTangents) {
						this.tangents = calculateTangents(positions, normals, uvs, indices);
				}
		}
}

export { BoxGeometry };