Limitation on body shapes / multi-element bodies

Physics
#1

Is there a limit to the number of elements which can be added to a multi-element body?

I am noticing an offset of some body elements when I have >5.

#2

Having looked into the documentation, it may appear as though I’ve not read deeply enough into the implications.

Given this quote, “When creating multi-element bodies, each element must be specified as a separate polygonal shape.” from here:

https://docs.coronalabs.com/guide/physics/physicsBodies/index.html#multi-element-bodies

I would like to know if this is implying that different body elements cannot be reliably used together, for example can you construct a body using all of the following at the same time:

For example, I think introducing a rectangular (‘box’) shape into a multi-element body causes problems, unless it’s done last. The following code should produce the same shaped bodies, but the second has a strange offset to one of the elements:

local physics = require("physics") physics.start() physics.setGravity(0,0) physics.setDrawMode("hybrid") local a = display.newGroup() a.x, a.y = 200, 200 physics.addBody( a, "static", { shape={ 100, 100, 200, 100, 200, 200, 100, 200 } }, { box={ x=250, y=150, halfWidth=50, halfHeight=50, angle=0 } } ) local b = display.newGroup() b.x, b.y = 200, 400 physics.addBody( b, "static", { box={ x=250, y=150, halfWidth=50, halfHeight=50, angle=0 } }, { shape={ 100, 100, 200, 100, 200, 200, 100, 200 } } )
#3

Let me see what I can find out for you.

Rob

#4

@horacebury, can you put that in a .zip file with a config.lua and build.settings and use the Report a bug link at the top of the page?  This doesn’t sound familiar to our engineers, so we will need to take a deeper dive into it.

But at least for now, it seems you have a potential work around.

Rob

#5

Yes, in short the bug appears when different types of shape (shape, box, outline, etc) are used when defining a single body. If only one type is used the problem goes away (…at least for the case of ‘shape’, which is the only one I’ve tried.)

#6

I guess this why tools like PhysicsEditor don’t cause problems because they are almost always multi-polygon shaped bodies.  Anyway thanks for submitting the bug report, as a reference, here is the case ID 13247833.

Rob

#7

Having looked into the documentation, it may appear as though I’ve not read deeply enough into the implications.

Given this quote, “When creating multi-element bodies, each element must be specified as a separate polygonal shape.” from here:

https://docs.coronalabs.com/guide/physics/physicsBodies/index.html#multi-element-bodies

I would like to know if this is implying that different body elements cannot be reliably used together, for example can you construct a body using all of the following at the same time:

For example, I think introducing a rectangular (‘box’) shape into a multi-element body causes problems, unless it’s done last. The following code should produce the same shaped bodies, but the second has a strange offset to one of the elements:

local physics = require("physics") physics.start() physics.setGravity(0,0) physics.setDrawMode("hybrid") local a = display.newGroup() a.x, a.y = 200, 200 physics.addBody( a, "static", { shape={ 100, 100, 200, 100, 200, 200, 100, 200 } }, { box={ x=250, y=150, halfWidth=50, halfHeight=50, angle=0 } } ) local b = display.newGroup() b.x, b.y = 200, 400 physics.addBody( b, "static", { box={ x=250, y=150, halfWidth=50, halfHeight=50, angle=0 } }, { shape={ 100, 100, 200, 100, 200, 200, 100, 200 } } )
#8

Let me see what I can find out for you.

Rob

#9

@horacebury, can you put that in a .zip file with a config.lua and build.settings and use the Report a bug link at the top of the page?  This doesn’t sound familiar to our engineers, so we will need to take a deeper dive into it.

But at least for now, it seems you have a potential work around.

Rob

#10

Yes, in short the bug appears when different types of shape (shape, box, outline, etc) are used when defining a single body. If only one type is used the problem goes away (…at least for the case of ‘shape’, which is the only one I’ve tried.)

#11

I guess this why tools like PhysicsEditor don’t cause problems because they are almost always multi-polygon shaped bodies.  Anyway thanks for submitting the bug report, as a reference, here is the case ID 13247833.

Rob