Physics accuracy

Physics
#1

Hi,

I started trying out Corona 2 hours ago so I’m kind of green and this is probably a dumb question, but here goes…

I’m not entirely satisfied with how the physics seems to work in the example below:

local physics = require("physics") physics.start() local ground = display.newRect(display.contentWidth / 2, display.contentHeight-20, display.contentWidth, 3) physics.addBody(ground, "static", { density=1.0, friction=0.5, bounce=0.0}) local function spawnCoins()     local coin = display.newImage("coin.png")     coin.x = math.random(display.contentWidth/8) + display.contentWidth/2      coin.y = -50     physics.addBody(coin, { density=2.0, friction=0.3, bounce=0.3}) end timer.performWithDelay(250, spawnCoins, 15)  

The result of this code is a pile of coins, but more often than not many of them are floating a bit above the coin below for some reason (see the physics.jpg image).

The coin.png image is 60x60 pixels and I’ve set the physics radius to 30. I would have thought that this would ensure some quite nice collisions.

Am I making a simple mistake or is the coin.png image wrong or is this just what we can expect from the physics engine?

#2

Use the below flag in the beginning of your main.lua file to see the actual physics outlines from your objects:

physics.setDrawMode("hybrid")
#3

Hi @runew,

These coins are round objects, but your actual internal physics bodies are rectangular (default). You need to tell Corona (Box2D) to use a radial-shaped body on these objects. This is done by adding a radius property to your body declaration (in the properties table):

[lua]

physics.addBody( coin, { radius=20, density=2.0, friction=0.3, bounce=0.3 } )

[/lua]

The value of this should match (or come close) to the visual size of the coins, which you can check by inspecting the hybrid mode as @Panc mentions.

Take care,

Brent

#4

Thanks a lot - both of you  :slight_smile:

#5

Use the below flag in the beginning of your main.lua file to see the actual physics outlines from your objects:

physics.setDrawMode("hybrid")
#6

Hi @runew,

These coins are round objects, but your actual internal physics bodies are rectangular (default). You need to tell Corona (Box2D) to use a radial-shaped body on these objects. This is done by adding a radius property to your body declaration (in the properties table):

[lua]

physics.addBody( coin, { radius=20, density=2.0, friction=0.3, bounce=0.3 } )

[/lua]

The value of this should match (or come close) to the visual size of the coins, which you can check by inspecting the hybrid mode as @Panc mentions.

Take care,

Brent

#7

Thanks a lot - both of you  :slight_smile: