vector.abs

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Oil_boi
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vector.abs

by Oil_boi » Post

Here is a simple code that can be added into the lua code to return an absolute vector

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--this converts a vector into absolute value
function vector.abs(vector)
	vector.x = math.abs(vector.x)
	vector.y = math.abs(vector.y)
	vector.z = math.abs(vector.z)
	return(vector)
end
I can't find where the vector library is stored in the game engine so I'll just post this here and hope someone makes a github pull request to add it in ¯\_(ツ)_/¯
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Re: vector.abs

by sfan5 » Post

Oil_boi wrote:I can't find where the vector library is stored in the game engine
Right here: https://github.com/minetest/minetest/bl ... vector.lua
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Re: vector.abs

by Hume2 » Post

sfan5 wrote:
Oil_boi wrote:I can't find where the vector library is stored in the game engine
Right here: https://github.com/minetest/minetest/bl ... vector.lua
I think, you confused that with the function vector.length. What OP says is not any kind of norm. It only makes all coordinates positive.
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Re: vector.abs

by Oil_boi » Post

Hume2 wrote:
sfan5 wrote:
Oil_boi wrote:I can't find where the vector library is stored in the game engine
Right here: https://github.com/minetest/minetest/bl ... vector.lua
I think, you confused that with the function vector.length. What OP says is not any kind of norm. It only makes all coordinates positive.
This can be used for collision detection

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pos = vector.new(0,0,0)
pos2 = vector.new(0.5,0,0)
instead of checking like:

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diff = vector.subtract(pos,pos2)
if diff.x < 0.5 and diff.x > -0.5 and diff.z < 0.5 and diff.z > -0.5 do
you can check like

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diff = vector.abs(vector.subtract(pos,pos2))
if diff.x < 0.5 and diff.z < 0.5 then
I specifically utilize this function in these locations:
https://github.com/oilboi/Crafter/blob/ ... on.lua#L56
https://github.com/oilboi/Crafter/blob/ ... te.lua#L61
https://github.com/oilboi/Crafter/blob/ ... te.lua#L74

Also I did a pull request
https://github.com/minetest/minetest/pull/9551
Last edited by Oil_boi on Wed Mar 25, 2020 20:49, edited 1 time in total.
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Re: vector.abs

by Hume2 » Post

This can be actually done even easier by using the maximum norm:

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function vector.maxnorm(v)
    return math.max(math.abs(v.x), math.max(math.abs(v.y), math.abs(v.z)))
end
Then it reduces to:

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norm = vector.maxnorm(vector.multiply(vector.subtract(pos, pos2), {x=2, y=0, z=2}))
if norm < 1 then
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Re: vector.abs

by Oil_boi » Post

Hume2 wrote:This can be actually done even easier by using the maximum norm:

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function vector.maxnorm(v)
    return math.max(math.abs(v.x), math.max(math.abs(v.y), math.abs(v.z)))
end
Then it reduces to:

Code: Select all

norm = vector.maxnorm(vector.multiply(vector.subtract(pos, pos2), {x=2, y=0, z=2}))
if norm < 1 then
Yes that is very good, but it's not modular as you can't recover the actual value of Y as it was before maxnorming it, but that would be a nice function to have
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Re: vector.abs

by AspireMint » Post

what about vector.distance(p1, p2) < 0.5

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Re: vector.abs

by Hume2 » Post

AspireMint wrote:what about vector.distance(p1, p2) < 0.5
This calculates the Eucleidan distance, not the maximum norm distance. Please, read the OP toughly to see what the vector.abs actually does.
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Re: vector.abs

by Oil_boi » Post

I just decided to make a video on it: https://youtu.be/2GOsXSeNgQw
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Re: vector.abs

by GreenXenith » Post

vector.apply(v, math.abs) but ok.
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Re: vector.abs

by Oil_boi » Post

GreenDimond wrote:vector.apply(v, math.abs) but ok.
Well I see a lot of people saying this is redundant with the vector.apply function, but, as they say that, we also have:

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function vector.floor(v)
	return {
		x = math.floor(v.x),
		y = math.floor(v.y),
		z = math.floor(v.z)
	}
end

function vector.round(v)
	return {
		x = math.floor(v.x + 0.5),
		y = math.floor(v.y + 0.5),
		z = math.floor(v.z + 0.5)
	}
end
function vector.add(a, b)
	if type(b) == "table" then
		return {x = a.x + b.x,
			y = a.y + b.y,
			z = a.z + b.z}
	else
		return {x = a.x + b,
			y = a.y + b,
			z = a.z + b}
	end
end
Why do we have these? Because it's easier to type

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vector.round(v) 
rather than

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vector.apply(v, function(x) return(math.floor(x + 0.5)) end)

and also

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vector.add(a, b)
instead of

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local new_vector = {x=a.x+b.x,y=a.y+b.y,z=a.z+b.z}
It makes more logical sense for the library to contain functions to apply a basic bit of math to each vector coordinate rather than each programmer to define their own functions.

We could even boil it down even further using the logic that is applied in the responses to this. Why even have vector.new when we could run:

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v = {x=5,y=1,z=4}
Very simply, because it's much easier to type out:

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v = vector.new(5,1,4)
And along with the logic of what I've been trying to provide here, it is also easier to type and remember:

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vector.abs(v)
I dunno how to explain it any further, it's only 6 lines of codes. It doesn't cause any performance changes to the engine. It makes your life slightly easier. If someone doesn't want it, they could keep doing vector.apply(v, math.abs). I also thought everyone would like the small addition.

I dunno man ¯\_(ツ)_/¯
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