ChainShape Help

[Ranguna259]

Hello everyone, so I've been trying to do a ChainShape but it doesn't seem to work, here's how I coded it.

I have a variable, a, which has all the shape's coordinates from the first to the last:

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a=10,10,20,30,30,40,40,10

And I want to create a ChainShape with that variable, like this:

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shape.b=love.physics.newBody(world, 25,25,'static')
shape.s=love.physics.newChainShape(a)
shape.f=love.physics.newFixture(shape.b,shape.s)

but it gives me a blue screen with a box2d error, saying "count >= 3"

All codes are in their appropriated functions.

I want to know what I am doing wrong, and if you can could you write a little exemple on how to do a chainshape ? The wiki doesn't have one and I don't realy understand how it works.

Thanks for reading, and if this post was approved then thank you mod for approving it

[micha]

Shouldn't it be

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a={10,10,20,30,30,40,40,10}

and

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shape.s=love.physics.newChainShape(false,a)

?

[riidom]

Wouldn't this place the table as first parameter, where a number is expected, and leave all the other parameters to nil?

On a more general side, I would like to know, how I can extract values of a table into the parameter list of a function.
(either like in this example, or e.g. {200,100,50} into love.graphics.setColor)

Ranguna, the problem is if you write a = 1, 2, 3 then a is 1, while 2 and 3 just get skipped.

Edit: Like this it works

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a={10,10,20,30,30,40,40,10}

shape.s=love.physics.newChainShape(false,unpack(a))

[Ranguna259]

Wouldn't this place the table as first parameter, where a number is expected, and leave all the other parameters to nil?

On a more general side, I would like to know, how I can extract values of a table into the parameter list of a function.
(either like in this example, or e.g. {200,100,50} into love.graphics.setColor)

Ranguna, the problem is if you write a = 1, 2, 3 then a is 1, while 2 and 3 just get skipped.

Edit: Like this it works

Code: Select all

a={10,10,20,30,30,40,40,10}

shape.s=love.physics.newChainShape(false,unpack(a))

Yep that did the trick, as for your question then I'm thinking that it is the same process as the one you've explained, like so:

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color={200,100,50}
love.graphics.setColor(unpack(color))

You've said that "a" is 1 in your exemple but I don't think it goes like that, I think that "a" is (1,2,3) but when you use it in chainshape or any other code without the "unpack()" code, chainshape will identify (1,2,3) as the first coodinate and not just 1. löve might be lovely, but it's not bugfree

Anyways thanks for everyone's help, my problem has been resolved.
Thanks again

[Robin]

You've said that "a" is 1 in your exemple but I don't think it goes like that, I think that "a" is (1,2,3) but when you use it in chainshape or any other code without the "unpack()" code, chainshape will identify (1,2,3) as the first coodinate and not just 1. löve might be lovely, but it's not bugfree

No. riidom was right.

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a, b, c = 1, 2, 3 -- now a == 1, b == 2, c == 3
d = 1, 2, 3 -- now d == 1
e, f, g = 1 -- now e == 1, f == g == nil

Lists in Lua are a really fragile thing. The only thing you can use them for is multiple assignment (like in my first example), multiple return values and multiple trailing arguments to functions. Try anything else with them, and they get truncated.

This is not a bug in LÖVE, this is standard and expected behaviour of Lua.

[Ranguna259]

You've said that "a" is 1 in your exemple but I don't think it goes like that, I think that "a" is (1,2,3) but when you use it in chainshape or any other code without the "unpack()" code, chainshape will identify (1,2,3) as the first coodinate and not just 1. löve might be lovely, but it's not bugfree

No. riidom was right.

Code: Select all

a, b, c = 1, 2, 3 -- now a == 1, b == 2, c == 3
d = 1, 2, 3 -- now d == 1
e, f, g = 1 -- now e == 1, f == g == nil

Lists in Lua are a really fragile thing. The only thing you can use them for is multiple assignment (like in my first example), multiple return values and multiple trailing arguments to functions. Try anything else with them, and they get truncated.

This is not a bug in LÖVE, this is standard and expected behaviour of Lua.

Oh I see, thanks for explaining that