Help needed with liquidfun faucet

jumpjack

I wrote this little Excel Macro (attached) which allows converting an excel drawing into a Box2d/liquidfun drawing:




I would like to add a continuous flow of water in the environment, but unfortunately I found that the Box2d/liquidfun version included in Gideros is buggish, as it lacks some file and declarations (for example ParticleEmitter); so the example Faucet does not compile.
So I tried adding manually particles inside .Step() functio, but I don't understand how to use this function.
So I'm stuck. Any help?

Macro creates a testParticles.js file to be replaced to the original file in LFJS folder of BOX2d/Liquidfun distribution.

hgy29

jumpjack said:

I would like to add a continuous flow of water in the environment, but unfortunately I found that the Box2d/liquidfun version included in Gideros is buggish, as it lacks some file and declarations (for example ParticleEmitter);

If something is missing in Gideros this doesn't mean it is buggish, rather that no one ever felt the need to add it. The ParticleEmitter you are referring to isn't part of liquidfun API, it is a helper class for tests (it is located in the TestBed folder of liquidfun distribution). If you look at wat it does, it simply emits particles once ina while, using the createParticle call of a ParticleSystem object. This call is implemented in gideros (https://wiki.giderosmobile.com/index.php/B2.ParticleSystem:createParticle) , so you could mimic or recode the particle emitter yourself in lua.

jumpjack

I don't know LUA, so if I could find a full version of Liquidfun it would be better than starting from scratch learning a new language.
Do you know how I can fix Liquidfun inside Giderors distribution to get Faucet example working?

MoKaLux

@jumpjack take it one step at a time. Do something simple first with liquidfun so you understand the basics. Then add more cool stuff. I don't think liquidfun need fixing in gideros, it works exactly as box2d used to (same functions, …)

BTW gideros + excel + excel macros = great combo.

hgy29

jumpjack said:

I don't know LUA, so if I could find a full version of Liquidfun it would be better than starting from scratch learning a new language.

I am confused. Gideros is LUA based, so if you are looking for a liquidfun implementation for another language, I would say that you aren't at the right place here.

jumpjack

hgy29 said:

jumpjack said:

I don't know LUA, so if I could find a full version of Liquidfun it would be better than starting from scratch learning a new language.

I am confused. Gideros is LUA based, so if you are looking for a liquidfun implementation for another language, I would say that you aren't at the right place here.

I am confused too: there is a functional Javascript implementation of Liquidfun inside Gideros distribution. :-)

Anyway, how would I implement a liquidfun particles emitter in LUA/GIDEROS? Maybe I can do the remaining part (adding walls and water) by myself, but I need some help in adding a continuous flow of water particles.

oleg

@jumpjack
See examples that come with gideros:


I understand correctly?- -you want to port the game from JS to gideros?

@SinisterSoft Somewhere on the forum posted examples with fluid?

jumpjack

oleg said:

I understand correctly?- -you want to port the game from JS to gideros?

yes

jumpjack

Found LUA source of the particle example, in this folder:
gideros-master\samplecode\Physics\Particles (sorry, can't post links yet)

I attach the LUA file.
To test it online in the "emulator" you must remove the reference to the texture image:
ps1:setTexture(Texture.new("Bubble.png"))
http://giderosmobile.com/code/


Particles example in action:
giderosmobile.com/examples#Physics/Particles


Let's see how complex it is porting a Box2d source from JS to LUA...

jumpjack

The Particles demo alone, in the emulator:
http://giderosmobile.com/code/8WTfPOZfIgo7MzCON638yWVZElLzfWZv

jumpjack

Ok now I just have to figure out how to make bodies visible...
http://giderosmobile.com/code/BBuMB8hXPyFX278DYslZsy1wRmqEBP2u

Apart from this, does anybody know if I can set "buoyancy level", or "weight", or how they call it, of different particles in Box2d?

antix

@jumpjack To make a basic emitter in Lua you can do something like this...

require "box2d"   application:setScaleMode("letterbox"); application:setOrientation(application.LANDSCAPE_LEFT); application:setLogicalDimensions(600,800)   local cw, ch = application:getContentWidth(), application:getContentHeight() -- stage bounds   local world = b2.World.new(0, 9.8) -- create world   local ground = world:createBody({}) -- create ground body ground:createFixture({shape = b2.EdgeShape.new(0, ch, cw, ch), density = 0}) -- create an edge shape, and attach it to the ground body as a fixture ground:createFixture({shape = b2.EdgeShape.new(cw, 0, cw, ch), density = 0}) ground:createFixture({shape = b2.EdgeShape.new(0, 0, 0, ch), density = 0}) ground:createFixture({shape = b2.EdgeShape.new(0, 0, cw, 0), density = 0})   local ps1= world:createParticleSystem({radius = 5}) stage:addChild(ps1)   local emitter = { -- our humble emitter frequency = 0.10, -- how often to emit a particle (in seconds) counter = 0, -- keeping count of when to emit particle = { -- what this emitter emits flags = 0,--FLAG_WATER --+ FLAG_VISCOUS, position = {x = 100, y = 50}, velocity = {x = 0.0010, y = -0.0005}, color = 0x2266dd, alpha = 1, }, }   local function onEnterFrame(e) -- called every frame local dt = e.deltaTime -- time (in ms) since last enterframe event   local counter = emitter.counter + dt -- increase counter if counter >= emitter.frequency then -- if counter exceeds threshold.. local id = ps1:createParticle(emitter.particle) -- emit a waterdrop counter = 0 -- reset counter end emitter.counter = counter -- save counter   world:step(1/60, 8, 3) -- simulate end   stage:addEventListener(Event.ENTER_FRAME, onEnterFrame)

An interesting question came to mind while I was coding this.. "how does one remove a waterdrop when it goes off screen or down a plughole"?

My thought was to have a plughole physics object and any waterdrop that touched it shape would be destroyed. It seems however that particles are not able to partake in such collision detection so in turn it appears that using particles to simulate water wouldn't be viable if you wanted waterdrops to disappear when they went down a plughole.

Is there any way to make a plughole work with particles or would it only be possible using more traditional box2d objects?

jumpjack

isn't a particle automatically removed once it gets off the screen?

jumpjack

antix said:

@jumpjack To make a basic emitter in Lua you can do something like this...

Thanks for the code, I extended it a little to have a "general purpose faucet":

require "box2d"   application:setScaleMode("letterbox"); application:setOrientation(application.LANDSCAPE_LEFT); application:setLogicalDimensions(600,800)   local cw, ch = application:getContentWidth(), application:getContentHeight() -- stage bounds   local world = b2.World.new(0, 9.8) -- create world   local ground = world:createBody({}) -- create ground body ground:createFixture({shape = b2.EdgeShape.new(0, ch, cw, ch), density = 0}) -- create an edge shape, and attach it to the ground body as a fixture ground:createFixture({shape = b2.EdgeShape.new(cw, 0, cw, ch), density = 0}) ground:createFixture({shape = b2.EdgeShape.new(0, 0, 0, ch), density = 0}) ground:createFixture({shape = b2.EdgeShape.new(0, 0, cw, 0), density = 0})     local ps1= world:createParticleSystem({radius = 2}) stage:addChild(ps1)   local emitter = { -- our humble emitter flow = 100, -- number of particles emitted per second visible = false, -- for debugging put it to true to see particles while they are created counter = 0, -- keeping count of when to emit particle = { -- what this emitter emits flags = 0,--FLAG_WATER --+ FLAG_VISCOUS, position = {x = 100, y = 50}, velocity = {x = 0.0010, y = -0.0005}, color = 0x2266dd, alpha = 10, }, } local FaucetSize = 20; local TLX=emitter.particle.position.x-FaucetSize/2 local TLY=emitter.particle.position.y-FaucetSize/2 local BRX=emitter.particle.position.x+FaucetSize/2 local BRY=emitter.particle.position.y+FaucetSize/2   -- Physical faucet box (not visible): -- At least one side must be open to allow water pouring ground:createFixture({shape = b2.EdgeShape.new(TLX,TLY,BRX,TLY), density = 0}) -- TOP --ground:createFixture({shape = b2.EdgeShape.new(BRX,TLY,BRX,BRY), density = 0}) -- RIGHT ground:createFixture({shape = b2.EdgeShape.new(BRX,BRY,TLX,BRY), density = 0}) -- BOTTOM ground:createFixture({shape = b2.EdgeShape.new(TLX,BRY,TLX,TLY), density = 0}) -- LEFT   -- Visible faucet box (just graphics): local FaucetThickness = 3 local shape = Shape.new() if emitter.visible then shape:setFillStyle(Shape.NONE, 0xff0000) else shape:setFillStyle(Shape.SOLID, 0xff0000) end shape:setLineStyle(1, 0x0000ff, 1) shape:beginPath() shape:moveTo(TLX-FaucetThickness,TLY-FaucetThickness) shape:lineTo(BRX+FaucetThickness,TLY-FaucetThickness) shape:lineTo(BRX+FaucetThickness,BRY+FaucetThickness) shape:lineTo(TLX-FaucetThickness,BRY+FaucetThickness) shape:lineTo(TLX-FaucetThickness,TLY-FaucetThickness) shape:endPath() shape:setPosition(0,0) stage:addChild(shape)     local function onEnterFrame(e) -- called every frame local dt = e.deltaTime -- time (in ms) since last enterframe event   local counter = emitter.counter + dt -- increase counter if counter >= 1/emitter.flow then -- if counter exceeds threshold.. local id = ps1:createParticle(emitter.particle) -- emit a waterdrop counter = 0 -- reset counter end emitter.counter = counter -- save counter   world:step(1/60, 8, 3) -- simulate end   stage:addEventListener(Event.ENTER_FRAME, onEnterFrame)

Apollo14

wow btw one interesting liquidfun game came to my youtube recommendations: