Convert Vec2 to Vec3 and vice versa

[minggo]

Some API returns Vec2, and some API accepts Vec3. It is not convenient. So need a way to convert types between Vec2 and Vec3. There are two ways to achieve it:

• add constructor in Vec2 and Vec3, for example

class Vec2 {
    public constructor (v: Vec3);
}

class Vec3 {
    public constructor (v: Vec2);
}

• add util functions to convert them

public vec2ToVec3 (v: Vec2) : Vec3 {
    ...
}

public vec3ToVec2 (v: Vec3) : Vec2 {
    ...
}

I think add constructors is better.

Can refer to this forum topic for detail information.

[AnkoGo123]

In any case, these transformations should not be perceived by the user, but should be placed within your system for transformations

[minggo]

@AnkoGo123 these parameter are passed in by developers, how to not be perceived by the user? Could you please describe it in more detail? Thanks.

[stanleyljl]

How about add a toVec3 in vec2 & toVec2 in vec3? @minggo

[minggo]

How about add a toVec3 in vec2 & toVec2 in vec3? @minggo

It seems good to me. Could you please add function prototype?

[jareguo]

Re: https://forum.cocos.org/t/topic/145658

[1226085293]

在 vec2 中添加 toVec3 和在 vec3 中添加 toVec2 怎么样？@minggo

不明白为什么你觉得 toVecX 比构造更好点，那么比如 cc.Rect 这种数据结构呢？如果用 toVec2/toVec3，依旧只能 cc.v2(rect.x, rect.y), 用其他包含 x,y 属性的数据初始化也一样麻烦，但是只要 Vec2/Vec3 构造支持 { x?: number, y?: number, z?: number }，能支持现在以及之后所有包含 xyz 参数的数据直接初始化 Vec2/Vec3

[minggo]

@1226085293 we do not want to use duck type as possible. Duck type is bad for performance.

[1226085293]

@1226085293 we do not want to use duck type as possible. Duck type is bad for performance.

那么直接在构造内针对类型单独处理如何？示例如下

class Vec2 {
	x: number;
	y: number;
}
class Vec3 {
	x: number;
	y: number;
	z: number;
	constructor(value_: { x?: number; y?: number; z?: number }) {
		if (value_ instanceof Vec2) {
			this.x = value_.x;
			this.y = value_.y;
			this.z = 0;
		} else {
			this.x = value_.x ?? 0;
			this.y = value_.y ?? 0;
			this.z = value_.z ?? 0;
		}
	}
}

[minggo]

I think it is duck type too. Am i right?
And please use english in future.

[1226085293]

I think it is duck type too. Am i right? And please use english in future.

如果把初始化参数改成对象类型甚至还提高了性能，但是按照你们对兼容性的做法估计也不会改，按照现有的构造参数类型去改就会是你说的性能浪费

class Vec2 {
	x = 0;
	y = 0;
}

class Vec3 {
	x = 0;
	y = 0;
	z = 0;
	constructor(v: Vec3);

	constructor(x?: number, y?: number, z?: number);

	constructor(x?: number | Vec3, y?: number, z?: number) {
		if (typeof x === "object") {
			this.x = x.x;
			this.y = x.y;
			this.z = x.z;
		} else {
			this.x = x || 0;
			this.y = y || 0;
			this.z = z || 0;
		}
	}
}

class Vec3_2 {
	x = 0;
	y = 0;
	z = 0;
	constructor(value_: { x?: number; y?: number; z?: number }) {
		this.x = value_.x ?? 0;
		this.y = value_.y ?? 0;
		this.z = value_.z ?? 0;
	}
}

let for_n = 100000000;
{
	let time_start_n = Date.now();

	for (let k_n = 0; k_n < for_n; ++k_n) {
		new Vec3(k_n, k_n + 1);
	}

	console.log("Vec3 使用 number 初始化", Date.now() - time_start_n);
}

{
	let time_start_n = Date.now();
	let temp_v3 = new Vec3();
	for (let k_n = 0; k_n < for_n; ++k_n) {
		temp_v3.x = k_n;
		temp_v3.y = k_n + 1;
		temp_v3.z = k_n + 2;
		new Vec3(temp_v3);
	}

	console.log("Vec3 使用 Vec3 初始化", Date.now() - time_start_n);
}

{
	let time_start_n = Date.now();
	let temp_v2 = new Vec2();
	for (let k_n = 0; k_n < for_n; ++k_n) {
		temp_v2.x = k_n;
		temp_v2.y = k_n + 1;
		new Vec3(temp_v2.x, temp_v2.y);
	}

	console.log("Vec3 使用 Vec2 初始化", Date.now() - time_start_n);
}

{
	let time_start_n = Date.now();
	for (let k_n = 0; k_n < for_n; ++k_n) {
		new Vec3_2({
			x: k_n,
			y: k_n + 1,
		});
	}

	console.log("Vec3_2 使用 number 初始化", Date.now() - time_start_n);
}

{
	let time_start_n = Date.now();
	let temp_v3 = new Vec3_2({});
	for (let k_n = 0; k_n < for_n; ++k_n) {
		temp_v3.x = k_n;
		temp_v3.y = k_n + 1;
		temp_v3.z = k_n + 2;
		new Vec3_2(temp_v3);
	}

	console.log("Vec3_2 使用 Vec3_2 初始化", Date.now() - time_start_n);
}

{
	let time_start_n = Date.now();
	let temp_v2 = new Vec2();
	for (let k_n = 0; k_n < for_n; ++k_n) {
		temp_v2.x = k_n;
		temp_v2.y = k_n + 1;
		new Vec3_2(temp_v2);
	}

	console.log("Vec3_2 使用 Vec2 初始化", Date.now() - time_start_n);
}

[minggo]

So i think it is still better to implement it as static functions.

[minggo]

Sorry, i mean to implement it as member functions.