newWorld - what units does it use?

[Sslaxx]

Now, http://love2d.org/docs/love_physics_newWorld_1.html mentions width and height, but my question is quite simple - is this in pixels or is it in Box2D units?

[bartbes]

Whatever you chose, though by default scaling is enabled, allowing you to use pixels.

[Robin]

I believe the default unit is 1/30 of a meter.

[Sslaxx]

In other words, it uses Box2D units? So, if I had a fixed screen res of 800x600, and a unit size of 64pixels-per-metre, then love.physics.newWorld (800/64, 600/64) would be correct?

[Robin]

In other words, it uses Box2D units? So, if I had a fixed screen res of 800x600, and a unit size of 64pixels-per-metre, then love.physics.newWorld (800/64, 600/64) would be correct?

Nope, the default is 1/30th of a Box2D unit (B2D unit = meter). That makes it easier to avoid twiddling with scaling, and just say "a LÖVE unit equals one pixel on screen, thus 30 pixels = 1 meter".

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pixels <-> your own drawing scale <-> LÖVE units <-> World:getMeter() <-> Box2D units

So if you draw a 300 pixel image 1:1, and use the default of 30px/m, you use a shape of size:

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300px -> *1 -> 300px -> /30 -> 10 meter

Your specific question:

So, if I had a fixed screen res of 800x600, and a unit size of 64pixels-per-metre, then love.physics.newWorld (800/64, 600/64) would be correct?

That depents what "unit size" means. Is it World:setMeter(64)? Then, yes.

[Sslaxx]

I see an issue, or I think I do.

A new world object is created at a scale of 30px-per-metre, yes? So if I were to create a world using love.physics.newWorld (800/30, 600/30) and were then to rescale that world to, say, 64 pixels, what would happen to the scale of that world?

[Robin]

I see an issue, or I think I do.

A new world object is created at a scale of 30px-per-metre, yes? So if I were to create a world using love.physics.newWorld (800/30, 600/30) and were then to rescale that world to, say, 64 pixels, what would happen to the scale of that world?

I don't think setting the scale changes anything. You usually set the scale of the world only once, right after creating the world, which would result this:

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w = love.physics.newWorld (800/30, 600/30)
w:setMeter(64)

You wouldn't do that. So I don't think there is an issue. If you still think there is, please show me what it is exactly.