Rectangle issues

Getting Started Newbie Questions
#1

I have a rectangle that’s suppose to stop a ball from going down to the bottom of the screen . But soetimes the ball goes straight through the rectangle and I don’t know why or how to fix it .

local myRectangle = display.newRect( 100, 100, 50, 20 ) myRectangle:setFillColor( 0.5, 0.2, 0.2 ) physics.addBody(myRectangle, "static", {friction = 2, density=5}) -- touch listener function function myRectangle:touch( event ) if event.phase == "began" then display.currentStage:setFocus( self, event.id ) self.isFocus = true self.x0 = self.x self.y0 = self.y elseif( self.isFocus ) then local dx = event.x - event.xStart local dy = event.y - event.yStart self.x = self.x0 + dx self.y = self.y0 + dy if event.phase == "ended" then display.currentStage:setFocus( self, nil ) self.isFocus = false end end return true end

-- create image of a ball Ball = display.newCircle(100, 20, 10) physics.addBody(Ball, "dynamic", {bounce = 0.1, density=.1}) Ball:setFillColor( 1.5, 0.2, 0.2 ) Ball:setStrokeColor( 0, 0, 5 ) Ball:applyLinearImpulse( .1, .00, 0, 0)
#2

You should read the physics guides:

https://docs.coronalabs.com/daily/guide/index.html#physics

While I  suggest reading them all, but this one coversthe issue you are having:

https://docs.coronalabs.com/daily/guide/physics/physicsBodies/index.html

object.isBullet

object.isBullet is the boolean value for whether the body should be treated as a “bullet” in respect to collision detection. Bullets are subject to continuous collision detection rather than periodic detection. This is computationally more expensive, but it can prevent fast-moving objects from passing through solid barriers.

#3

as per @roaminggamer making your Ball a bullet will prevent tunneling when the myRectangle is stationary, but…

 self.x = self.x0 + dx self.y = self.y0 + dy 

  when you directly alter the x/y of a physics object it is like instantaneously “teleporting” it - the physics engine doesn’t get a chance to “see” the delta movement (because IT didn’t do it, via a force, for example) and so you can teleport right “through” another physics object without collision detection or response, even bullets.

  (because technically it DIDN’T move “through” the other object, it sort of hyperdimensionaly teleported “around” it, at least as far as the physics engine is aware)

   the solution is complicated… the short answer it to avoid this type of teleporting, but to do so you may need to make your box dynamic and apply a touch joint (or other impulses created manually to accomplish your touch drag) along with fixed rotation, probably some damping, adjusting relative masses, etc – expect a fair amount of “tuning” required to get the right “feel”.

#4

I put the rectangle as bullet it didn’t work and then I put both the Ball and rectangle as bullet and it doesn’t work 

#5

And… you read the guide right?

Oh, and how are you moving the ‘bullet’?

As @davebollinger correctly points out:

If you’re moving any part of this conglomeration using manual discrete changes you’ll probably get tunneling.

I see you’ve got the exact code I gavein my example showing you how to stop the ‘wall’ from moving.

I added this bit:

 self.x = self.x0 + dx self.y = self.y0 + dy

To allow you to try the example over and over to see that it did indeed stop moving when you lifted your finger.

It isn’t going to be correct to use that for some kind of interaction.

In short, you have to use all physics movement to make a paddle (which is what you sound like your trying to do).

#6

yes

#7 
-- create image of a ball Ball = display.newCircle(100, 20, 10) physics.addBody(Ball, "dynamic", {bounce = 0.1, density=.1}) Ball:setFillColor( 1.5, 0.2, 0.2 ) Ball:setStrokeColor( 0, 0, 5 ) Ball.isBullet = true Ball:applyLinearImpulse( .1, .00, 0, 0)
#8 
-- create object local myRectangle = display.newRect( 100, 100, 70, 15 ) myRectangle:setFillColor( 0.5, 0.2, 0.2 ) physics.addBody(myRectangle, "static", {friction = 2, density=5}) -- touch listener function function myRectangle:touch( event ) if event.phase == "began" then display.currentStage:setFocus( self, event.id ) self.isFocus = true self.x0 = self.x self.y0 = self.y elseif( self.isFocus ) then local dx = event.x - event.xStart local dy = event.y - event.yStart self.x = self.x0 + dx self.y = self.y0 + dy if event.phase == "ended" then display.currentStage:setFocus( self, nil ) self.isFocus = false end end return true end
#9

How do I make the objects solid ?

#10

yeah, I’ve got nothing else.  I don’t have a clear picture of what you want the full gamut of interactions to be.

If you’re not doing discrete movements, is bullet should work. 

I’d check the size and thickness of my physics bodies.

Failing that, I’d look into the API (https://docs.coronalabs.com/daily/api/library/physics/index.html) and pay particular attention to:

physics.setPositionIterations()

physics.setVelocityIterations()

#11

Solid?  Solid is not a concept in Box2D.

There are two major attributes to Box2D physics simulation (and for most other simulated game physics engines too):

  • Collision Detection - The engine determines there was a collision (or will be) and fires an event.
    • Corona SDK has the concept of ‘listeners’.  i.e. Code listening for events.
    • You choose what actions to take in listeners when a collision is detected.
  • Collision Response - This is the physical part we normally associate with real world physics: bouncing, pushing, etc.
    • By default, all objects that can collide with each other respond to those collisions.
    • By default, all bodies collide with all other bodies, but this can be changed via the filter when adding a body.
    • Additionally, if you set ‘isSensor’ to true, the ‘response’ part of Box2D is turned off for that object.  Only detection works.  By default, isSensor is false.

You must also understand that collision detection is discrete and not continuous. 

That is, where in the real world an object moves like this:

:lol: ---------------------------------------> :lol:

In the simulated environment, it is more like this:

:blink:              ??               ??                :blink:

t0                 t1                t2                t3  

This means, that in the real world for a time between t2 and t3, the object’s position is known.  In the simulated world it must be interpolated.

This in turn means that collisions, which are only checked at discrete times can miss a collision.  This is where the concept of tunneling comes from.

At the end of the day, you must know this to properly create a game that will detect and respond to collisions when you want it to.

PS - Going offline.  No further responses will be forthcoming till later.

#12

How can I make it thick enough for the ball to not go through ? This is what I have now :

local myRectangle = display.newRect( 100, 100, 70, 15 ) myRectangle:setFillColor( 0.5, 0.2, 0.2 ) physics.addBody(myRectangle, "static", {hasBody = true, friction = 2, density=5})

-- create image of a ball Ball = display.newCircle(100, 20, 10) physics.addBody(Ball, "dynamic", {radius=10, bounce = 0.1, density=.1}) Ball:setFillColor( 1.5, 0.2, 0.2 ) Ball:setStrokeColor( 0, 0, 5 ) Ball.isBullet = true Ball:applyLinearImpulse( .1, .00, 0, 0)
#13

I modified your code slightly and am not seeing a penetration/tunneling issue.

 

local physics=require("physics") physics.start() physics.setGravity( 0, 0 ) --physics.setDrawMode('hybrid') local rect = display.newRect( display.contentCenterX, display.contentCenterY, 70, 15 ) rect:setFillColor( 0.5, 0.2, 0.2 ) physics.addBody(rect, "static", { friction = 2, density=5 } ) local ball = display.newCircle( display.contentCenterX, display.contentCenterY - 150, 10) physics.addBody(ball, "dynamic", {radius=10, bounce = 0.1, density=.1}) ball:setFillColor( 1.5, 0.2, 0.2 ) ball:setStrokeColor( 0, 0, 5 ) ball.isBullet = true ball:applyLinearImpulse( 0, 100 \* ball.mass, ball.x, ball.y )
#14

That doesn’t work . The ball bounces up from the rectangle once and the moves very slowly until it hits the rectangle and then nothing else happens .

#15

I’m aware of that.  I wasn’t trying to solve your problem.
 
I was trying to demonstrate that there is not a problem with passing through the block.
 
I also fixed several errors in your general use of Corona.  If you apply the concepts you see in my code to yours, you’ll probably be closer to the solution you want.
 
You’ve asserted that something is happening that is not happening.  There is no way you should be getting tunneling.
 
You’re doing a few small wrong things in your code:

physics.addBody(myRectangle, "static", {hasBody = true, friction = 2, density=5})

should be

physics.addBody(myRectangle, "static", { friction = 2, density=5})

hasBody is not a physics parameter
 
I don’t know what you’re trying to do here, but I know it is wrong:

-- Why are you moving it to the right? -- Why no leading zero? .1 should be 0.1 for legibility -- last two args should be: Ball.x, Ball.y instead of 0,0 Ball:applyLinearImpulse( .1, .00, 0, 0)

AT THE END OF THE DAY THERE IS NO ISSUE WITH CORONA, PHYSICS, OR TUNNELING.

#16

The ball still does go through the rectangle and the finish line is on the right so I want the ball to move to the right 

#17

If you create the ball in the same position as the rectangle it will be force moved somewhere else by the physics engine.  That could be what you’re seeing.

#18

There not positioned in the same place :

-- create image of a ball local ball = display.newCircle( display.contentCenterX, display.contentCenterY - 150, 10) ball.x = 100 ball.y = 200 physics.addBody(ball, "dynamic", {radius=10, bounce = 0.1, density=.1}) ball:setFillColor( 1.5, 0.2, 0.2 ) ball:setStrokeColor( 0, 0, 5 ) ball.isBullet = true ball:applyLinearImpulse( 0, 100 \* ball.mass, ball.x, ball.y )

local myRectangle = display.newRect( display.contentCenterX, display.contentCenterY, 70, 15 ) myRectangle:setFillColor( 0.5, 0.2, 0.2 ) physics.addBody(myRectangle, "static", { friction = 2, density=5})
#19

You should read the physics guides:

https://docs.coronalabs.com/daily/guide/index.html#physics

While I  suggest reading them all, but this one coversthe issue you are having:

https://docs.coronalabs.com/daily/guide/physics/physicsBodies/index.html

object.isBullet

object.isBullet is the boolean value for whether the body should be treated as a “bullet” in respect to collision detection. Bullets are subject to continuous collision detection rather than periodic detection. This is computationally more expensive, but it can prevent fast-moving objects from passing through solid barriers.

#20

as per @roaminggamer making your Ball a bullet will prevent tunneling when the myRectangle is stationary, but…

 self.x = self.x0 + dx self.y = self.y0 + dy 

  when you directly alter the x/y of a physics object it is like instantaneously “teleporting” it - the physics engine doesn’t get a chance to “see” the delta movement (because IT didn’t do it, via a force, for example) and so you can teleport right “through” another physics object without collision detection or response, even bullets.

  (because technically it DIDN’T move “through” the other object, it sort of hyperdimensionaly teleported “around” it, at least as far as the physics engine is aware)

   the solution is complicated… the short answer it to avoid this type of teleporting, but to do so you may need to make your box dynamic and apply a touch joint (or other impulses created manually to accomplish your touch drag) along with fixed rotation, probably some damping, adjusting relative masses, etc – expect a fair amount of “tuning” required to get the right “feel”.