Hello,
I've been having some trouble getting my particle emitter to emit particles from correct position after setting it to follow my "player" object.
Here's the case: I've created a turret object which has body and changeable weapon (one or more barrels). The body and barrels have been inserted in to same group which is my "player" object/group.
Then I've placed the player group to correct spot on the screen and rotating the whole group (body and barrel(s) are turning at the same time) and it's working.
But when I set my emitter to follow this player group it emits particles from the center reference point (default). Of course I can change the reference point to, for example top center, but then my player group also rotates around that point => not what I want.
So what is the correct way of doing this? I do need my turret to consist of 2 or more objects because I want to be able to attach more stuff to it like additional turrets etc. Still I would like to use particle emitter(s) to emit ammunition...
Here's something I've been doing so far:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 | local M = {} local new = function () local stageHeight = display.contentHeight local stageWidth = display.contentWidth ------------------ -- Groups ------------------ local localGroup = display.newGroup() ------------------ -- Your code here ------------------ -- body of the turret which can have different type and number of barrels (weapons) local body = display.newImage("gun_turret_body.png") body.x = 0 body.y = 0 -- defender/turret group local defender = display.newGroup() -- table for weapons weapon = {} -- create turret (1 barrel) weapon["turret"] = display.newImage("turret_barrel.png") weapon["turret"].x = 0 weapon["turret"].y = -40 weapon["turret"].isVisible = false --weapon["turret"]:setReferencePoint(display.TopCenterReferencePoint) -- create machinegun, 2 barrels local barrel1 = display.newImage("turret_barrel_small.png") local barrel2 = display.newImage("turret_barrel_small.png") local machinegun = display.newGroup() machinegun:insert(barrel1) machinegun:insert(barrel2) barrel1.x = -20 barrel2.x = 20 weapon["machinegun"] = machinegun weapon["machinegun"].x = 0 weapon["machinegun"].y = -50 weapon["machinegun"].isVisible = false -- insert weapons into defender-group defender:insert(weapon["turret"]) defender:insert(weapon["machinegun"]) defender:insert(body) -- place defender (turret group) to right place defender.x = stageWidth/2 defender.y = stageHeight-30 defender.rotation = 0 --defender:setReferencePoint(display.TopCenterReferencePoint) -- Setting reference point for turret group makes following emitter to be in correct place but then turret rotation is wrong -- handle turret firing (only rotates defender/turret group for now) local fireTurret = function(event, angle) print("fireTurret") if event.phase == "began" then transition.to(defender, { rotation = angle, time = 300, onComplete = function(self) end } ) end end -- assign firing function for each weapon weapon["turret"].fire = fireTurret weapon["machinegun"].fire = fireTurret -- CREATE AN EMITTER (NAME, SCREENW, SCREENH, ROTATION, ISVISIBLE, LOOP) Particles.CreateEmitter("TurretEmitter", 0, 0, 0, true, true) -- DEFINE PARTICLE TYPE local Properties = {} Particles.CreateParticleType ("Shots", { imagePath = "shot.png", imageWidth = 32, imageHeight = 32, velocityStart = 350, autoOrientation = true, killOutsideScreen = true, lifeTime = 3000, alphaStart = 1.00, -- APPLY PHYSICS: PhysicsMaterial = { density = 0, friction = 0, bounce = 0 }, PhysicsProperties = { isFixedRotation = true, isSleepingAllowed = true, bodyType = "kinematic", isSensor = true, name = "SHOT" } } ) -- FEED EMITTER (EMITTER NAME, PARTICLE TYPE NAME, EMISSION RATE, DURATION, DELAY) Particles.AttachParticleType("TurretEmitter", "Shots", 10, 99999, 0) -- TELL EMITTER TO FOLLOW Particles.SetEmitterTarget( "TurretEmitter", defender, true, 0 ) -- follows defender/turret group atm but emitter is in the center... --Particles.SetEmitterTarget( "TurretEmitter", weapon["turret"], true, 0 ) -- If turret weapon is the target, the emitter will follow turret (barrel) but in its own coordinates 0, -40 so not shown in the screen -- So am I doing something wrong when constructing weapon's this way and then rotation the whole defender/turret group? local emitter = Particles.GetEmitter("TurretEmitter") emitter.y = -70 -- this does not seem to change emitter's position because SetEmitterTarget is used... -- start turret emitter Particles.StartEmitter("TurretEmitter", false) -- AUTO UPDATE PARTICLE ENGINE Particles.StartAutoUpdate() -- Create player which holds only some player attributes local player = {} player.current_weapon = "turret" -- current selected weapon, which will be set visible -- show weapon that is selected weapon[player.current_weapon].isVisible = true; -- background image local background = display.newImage("background.png") -- calculate angle for turret local PI = 180 / (4*math.atan(1)) local fireWeapon = function( event ) local angle = ( math.atan2( (defender.y-event.y), (defender.x-event.x) ) * PI ) - 90 -- fire selected weapon (rotate barrel atm with following emitter) weapon[player.current_weapon].fire(event, angle) end -- add event listener for weapon firing background:addEventListener("touch", fireWeapon) ------------------ -- MUST return a display.newGroup() ------------------ return localGroup end M.new = new return M |
views:1455 update：2011/11/18 8:53:10