How many metres big are box2d objects?

john26

I've been reading the Box2D website docs recently and it says to do everything in SI units with simulation objects restricted to roughly 0.1 to 10m in size. They warn against using pixels for dimensions. So I was wondering, if I define a Gideros body of size 100x100 pixels, how many metres big is it? Does Gideros use a scaling factor here?

ar2rsawseen

@john26 yes Gideros is using scaling factor automatically for positions and dimensions.
The default scaling factor is 30, thus making your 100px body a 3.3 meters big.

You can provide your own scaling using b2.setScale method.

Here are more discussions on this topic:
http://www.giderosmobile.com/forum/discussion/comment/3231#Comment_3231
http://www.giderosmobile.com/forum/discussion/1311/box2d-scaling-factor#Item_8

john26

I see thanks very much! When I read the Box2D website and it said "don't use pixels" I thought I was in trouble. But it seems Gideros was quietly sorting everything out behind the scenes (as usual).

I guess if using automatic image resolution, this would be an extra factor on top of the x30 scaling?

ar2rsawseen

@john26 well using letterboxed automatic scaling with auto image resolution would affect only visual part, nothing will change on the box2d calculation size.

However other screen scaling types might mess up something, it all depends on how you create bodies and tie them to the visual representation.