Hi, today a quick post about how to create a ladder for the Citrus Engine.
It is a preview version, Michael Kerr requested me for his flash game scripting class !
I’m working with Eric to add it into the original package !!
So here is the result : the ladder in action
A ladder is a simple sensor object.
Here are the specifications :
– a ladder is a Sensor, on contact it will give the capacity for the hero to climb/down. It removes it after contact.
– it will remove hero’s gravity when it will be on the ladder and restore it after contact.
– the hero can’t duck on a ladder, but it can always jump.
– the ladder mode should not be “enabled” until the player presses “up” or “down” depending on where they are vertically. That way they can jump past it.
– as soon as the player “connects to” the ladder, they should be translated smoother to the center of the ladder so they are climbing up/down the center of it.
– when coming from the top to go down, there will be a platform, and the ladder over. I disable contact with this platform if the hero uses the ladder.
– there are 3 ladder animations (ladderIdle, ladderClimbUp, and ladderClimbDown)
So I update the Sensor like that :
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 | package com.citrusengine.objects.platformer { import Box2DAS.Dynamics.ContactEvent; import Box2DAS.Dynamics.b2Body; import flash.display.MovieClip; import com.citrusengine.objects.PhysicsObject; import org.osflash.signals.Signal; /** * Sensors simply listen for when an object begins and ends contact with them. They disaptch a signal * when contact is made or ended, and this signal can be used to perform custom game logic such as * triggering a scripted event, ending a level, popping up a dialog box, and virtually anything else. * * Remember that signals dispatch events when ANY Box2D object collides with them, so you will want * your collision handler to ignore collisions with objects that it is not interested in, or extend * the sensor and use maskBits to ignore collisions altogether. * * Events * onBeginContact - Dispatches on first contact with the sensor. * onEndContact - Dispatches when the object leaves the sensor. */ public class Sensor extends PhysicsObject { /** * Dispatches on first contact with the sensor. */ public var onBeginContact:Signal; /** * Dispatches when the object leaves the sensor. */ public var onEndContact:Signal; public var isLadder:Boolean = false; public static function Make(name:String, x:Number, y:Number, width:Number, height:Number, view:* = null):Sensor { if (view == null) view = MovieClip; return new Sensor(name, { x: x, y: y, width: width, height: height, view: view } ); } public function Sensor(name:String, params:Object=null) { super(name, params); onBeginContact = new Signal(ContactEvent); onEndContact = new Signal(ContactEvent); } override public function destroy():void { onBeginContact.removeAll(); onEndContact.removeAll(); _fixture.removeEventListener(ContactEvent.BEGIN_CONTACT, handleBeginContact); _fixture.removeEventListener(ContactEvent.END_CONTACT, handleEndContact); super.destroy(); } override protected function defineBody():void { super.defineBody(); _bodyDef.type = b2Body.b2_staticBody; } override protected function defineFixture():void { super.defineFixture(); _fixtureDef.isSensor = true; } override protected function createFixture():void { super.createFixture(); _fixture.m_reportBeginContact = true; _fixture.m_reportEndContact = true; _fixture.addEventListener(ContactEvent.BEGIN_CONTACT, handleBeginContact); _fixture.addEventListener(ContactEvent.END_CONTACT, handleEndContact); } protected function handleBeginContact(e:ContactEvent):void { onBeginContact.dispatch(e); } protected function handleEndContact(e:ContactEvent):void { onEndContact.dispatch(e); } } } |
Adding a proprety to it : public var isLadder:Boolean = false;
I update the hero class too:
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 | package com.citrusengine.objects.platformer { import Box2DAS.Common.V2; import Box2DAS.Dynamics.ContactEvent; import Box2DAS.Dynamics.b2Body; import Box2DAS.Dynamics.b2Fixture; import com.citrusengine.math.MathVector; import com.citrusengine.objects.PhysicsObject; import com.citrusengine.physics.CollisionCategories; import org.osflash.signals.Signal; import flash.display.MovieClip; import flash.ui.Keyboard; import flash.utils.clearTimeout; import flash.utils.getDefinitionByName; import flash.utils.setTimeout; /** * This is a common, simple, yet solid implementation of a side-scrolling Hero. * The hero can run, jump, get hurt, and kill enemies. It dispatches signals * when significant events happen. The game state's logic should listen for those signals * to perform game state updates (such as increment coin collections). * * Don't store data on the hero object that you will need between two or more levels (such * as current coin count). The hero should be re-created each time a state is created or reset. */ public class Hero extends PhysicsObject { //properties // properties for ladder public var originalGravity:Number = 1.6; public var canClimb:Boolean = false; public var climbVelocity:Number = 5; public var ladder:Sensor; protected var _onLadder:Boolean = false; protected var _climbing:Boolean = false; protected var _climbAnimation:String = "ladderIdle"; //end properties for ladder /** * This is the rate at which the hero speeds up when you move him left and right. */ public var acceleration:Number = 1; /** * This is the fastest speed that the hero can move left or right. */ public var maxVelocity:Number = 8; /** * This is the initial velocity that the hero will move at when he jumps. */ public var jumpHeight:Number = 14; /** * This is the amount of "float" that the hero has when the player holds the jump button while jumping. */ public var jumpAcceleration:Number = 0.9; /** * This is the y velocity that the hero must be travelling in order to kill a Baddy. */ public var killVelocity:Number = 3; /** * The y velocity that the hero will spring when he kills an enemy. */ public var enemySpringHeight:Number = 10; /** * The y velocity that the hero will spring when he kills an enemy while pressing the jump button. */ public var enemySpringJumpHeight:Number = 12; /** * How long the hero is in hurt mode for. */ public var hurtDuration:Number = 1000; /** * The amount of kick-back that the hero jumps when he gets hurt. */ public var hurtVelocityX:Number = 6; /** * The amount of kick-back that the hero jumps when he gets hurt. */ public var hurtVelocityY:Number = 10; //events /** * Dispatched whenever the hero jumps. */ public var onJump:Signal; /** * Dispatched whenever the hero gives damage to an enemy. */ public var onGiveDamage:Signal; /** * Dispatched whenever the hero takes damage from an enemy. */ public var onTakeDamage:Signal; /** * Dispatched whenever the hero's animation changes. */ public var onAnimationChange:Signal; /** * Determines whether or not the hero's ducking ability is enabled. */ public var canDuck:Boolean = true; protected var _groundContacts:Array = [];//Used to determine if he's on ground or not. protected var _enemyClass:Class = Baddy; protected var _onGround:Boolean = false; protected var _springOffEnemy:Number = -1; protected var _hurtTimeoutID:Number; protected var _hurt:Boolean = false; protected var _friction:Number = 0.75; protected var _playerMovingHero:Boolean = false; protected var _controlsEnabled:Boolean = true; protected var _ducking:Boolean = false; public static function Make(name:String, x:Number, y:Number, width:Number, height:Number, view:* = null):Hero { if (view == null) view = MovieClip; return new Hero(name, { x: x, y: y, width: width, height: height, view: view } ); } /** * Creates a new hero object. */ public function Hero(name:String, params:Object = null) { super(name, params); originalGravity = gravity; onJump = new Signal(); onGiveDamage = new Signal(); onTakeDamage = new Signal(); onAnimationChange = new Signal(); } override public function destroy():void { _fixture.removeEventListener(ContactEvent.PRE_SOLVE, handlePreSolve); _fixture.removeEventListener(ContactEvent.BEGIN_CONTACT, handleBeginContact); _fixture.removeEventListener(ContactEvent.END_CONTACT, handleEndContact); clearTimeout(_hurtTimeoutID); onJump.removeAll(); onGiveDamage.removeAll(); onTakeDamage.removeAll(); onAnimationChange.removeAll(); super.destroy(); } /** * Whether or not the player can move and jump with the hero. */ public function get controlsEnabled():Boolean { return _controlsEnabled; } public function set controlsEnabled(value:Boolean):void { _controlsEnabled = value; if (!_controlsEnabled) _fixture.SetFriction(_friction); } /** * Returns true if the hero is on the ground and can jump. */ public function get onGround():Boolean { return _onGround; } /** * The Hero uses the enemyClass parameter to know who he can kill (and who can kill him). * Use this setter to to pass in which base class the hero's enemy should be, in String form * or Object notation. * For example, if you want to set the "Baddy" class as your hero's enemy, pass * "com.citrusengine.objects.platformer.Baddy", or Baddy (with no quotes). Only String * form will work when creating objects via a level editor. */ public function set enemyClass(value:*):void { if (value is String) _enemyClass = getDefinitionByName(value as String) as Class; else if (value is Class) _enemyClass = value; } /** * This is the amount of friction that the hero will have. Its value is multiplied against the * friction value of other physics objects. */ public function get friction():Number { return _friction; } public function set friction(value:Number):void { _friction = value; if (_fixture) { _fixture.SetFriction(_friction); } } override public function update(timeDelta:Number):void { super.update(timeDelta); var velocity:V2 = _body.GetLinearVelocity(); if (controlsEnabled) { var moveKeyPressed:Boolean = false; _ducking = (_ce.input.isDown(Keyboard.DOWN) && _onGround && canDuck); if (_ce.input.isDown(Keyboard.RIGHT) && !_ducking) { if (canClimb) { gravity = originalGravity; _climbing = false; } velocity.x += (acceleration); moveKeyPressed = true; } if (_ce.input.isDown(Keyboard.LEFT) && !_ducking) { if (canClimb) { gravity = originalGravity; _climbing = false; } velocity.x -= (acceleration); moveKeyPressed = true; } _onLadder = ((_ce.input.isDown(Keyboard.DOWN) || _ce.input.isDown(Keyboard.UP)) && canClimb); if (_onLadder) { if (x < ladder.x) x++; if (x > ladder.x) x--; } if (_ce.input.isDown(Keyboard.UP) && canClimb) { _onLadder = _climbing = true; _climbAnimation = "ladderClimbUp"; velocity = new V2(0, 0); velocity.y -= climbVelocity; gravity = 0; moveKeyPressed = true; } if (_ce.input.isDown(Keyboard.DOWN) && canClimb) { _onLadder = _climbing = true; _climbAnimation = "ladderClimbDown"; velocity = new V2(0, 0); velocity.y += climbVelocity; gravity = 0; moveKeyPressed = true; } // Remove velocity if just stop climbing if ((_ce.input.justReleased(Keyboard.UP) || _ce.input.justReleased(Keyboard.DOWN)) && canClimb) { _climbAnimation = "ladderIdle"; velocity.y = 0; } if (canClimb && _ce.input.justPressed(Keyboard.SPACE)) { _climbing = false; gravity = originalGravity; velocity.y = -jumpHeight; onJump.dispatch(); } //If player just started moving the hero this tick. if (moveKeyPressed && !_playerMovingHero) { _playerMovingHero = true; _fixture.SetFriction(0); //Take away friction so he can accelerate. } //Player just stopped moving the hero this tick. else if (!moveKeyPressed && _playerMovingHero) { _playerMovingHero = false; _fixture.SetFriction(_friction); //Add friction so that he stops running } if (_onGround && _ce.input.justPressed(Keyboard.SPACE) && !_ducking) { velocity.y = -jumpHeight; onJump.dispatch(); } if (_ce.input.isDown(Keyboard.SPACE) && !_onGround && velocity.y < 0) { velocity.y -= jumpAcceleration; } if (_springOffEnemy != -1) { if (_ce.input.isDown(Keyboard.SPACE)) velocity.y = -enemySpringJumpHeight; else velocity.y = -enemySpringHeight; _springOffEnemy = -1; } //Cap velocities if (velocity.x > (maxVelocity)) velocity.x = maxVelocity; else if (velocity.x < (-maxVelocity)) velocity.x = -maxVelocity; //update physics with new velocity _body.SetLinearVelocity(velocity); } updateAnimation(); } /** * Returns the absolute walking speed, taking moving platforms into account. * Isn't super performance-light, so use sparingly. */ public function getWalkingSpeed():Number { var groundVelocityX:Number = 0; for each (var groundContact:b2Fixture in _groundContacts) { groundVelocityX += groundContact.GetBody().GetLinearVelocity().x; } return _body.GetLinearVelocity().x - groundVelocityX; } /** * Hurts the hero, disables his controls for a little bit, and dispatches the onTakeDamage signal. */ public function hurt():void { _hurt = true; controlsEnabled = false; _hurtTimeoutID = setTimeout(endHurtState, hurtDuration); onTakeDamage.dispatch(); //Makes sure that the hero is not frictionless while his control is disabled if (_playerMovingHero) { _playerMovingHero = false; _fixture.SetFriction(_friction); } } override protected function defineBody():void { super.defineBody(); _bodyDef.fixedRotation = true; _bodyDef.allowSleep = false; } override protected function defineFixture():void { super.defineFixture(); _fixtureDef.friction = _friction; _fixtureDef.restitution = 0; _fixtureDef.filter.categoryBits = CollisionCategories.Get("GoodGuys"); _fixtureDef.filter.maskBits = CollisionCategories.GetAll(); } override protected function createFixture():void { super.createFixture(); _fixture.m_reportPreSolve = true; _fixture.m_reportBeginContact = true; _fixture.m_reportEndContact = true; _fixture.addEventListener(ContactEvent.PRE_SOLVE, handlePreSolve); _fixture.addEventListener(ContactEvent.BEGIN_CONTACT, handleBeginContact); _fixture.addEventListener(ContactEvent.END_CONTACT, handleEndContact); } protected function handlePreSolve(e:ContactEvent):void { if (e.other.GetBody().GetUserData() is Platform && canClimb && (_climbing || !_onGround)) { if ((y + height / 2) < (ladder.y + ladder.height / 2)) { e.contact.Disable(); } } if (!_ducking) return; var other:PhysicsObject = e.other.GetBody().GetUserData() as PhysicsObject; var heroTop:Number = y; var objectBottom:Number = other.y + (other.height / 2); if (objectBottom < heroTop) e.contact.Disable(); } protected function handleBeginContact(e:ContactEvent):void { var colliderBody:b2Body = e.other.GetBody(); if (_enemyClass && colliderBody.GetUserData() is _enemyClass) { if (_body.GetLinearVelocity().y < killVelocity && !_hurt) { hurt(); //fling the hero var hurtVelocity:V2 = _body.GetLinearVelocity(); hurtVelocity.y = -hurtVelocityY; hurtVelocity.x = hurtVelocityX; if (colliderBody.GetPosition().x > _body.GetPosition().x) hurtVelocity.x = -hurtVelocityX; _body.SetLinearVelocity(hurtVelocity); } else { _springOffEnemy = colliderBody.GetPosition().y * _box2D.scale - height; onGiveDamage.dispatch(); } } if (colliderBody.GetUserData() is Sensor && colliderBody.GetUserData().isLadder) { canClimb = true; canDuck = false; ladder = colliderBody.GetUserData(); } //Collision angle if (e.normal) //The normal property doesn't come through all the time. I think doesn't come through against sensors. { var collisionAngle:Number = new MathVector(e.normal.x, e.normal.y).angle * 180 / Math.PI; if (collisionAngle > 45 && collisionAngle < 135) { _groundContacts.push(e.other); _onGround = true; } } } protected function handleEndContact(e:ContactEvent):void { //Remove from ground contacts, if it is one. var index:int = _groundContacts.indexOf(e.other); if (index != -1) { _groundContacts.splice(index, 1); if (_groundContacts.length == 0) _onGround = false; } if (e.other.GetBody().GetUserData() is Sensor && e.other.GetBody().GetUserData().isLadder) { _climbing = canClimb = false; canDuck = true; gravity = originalGravity; } } protected function endHurtState():void { _hurt = false; controlsEnabled = true; } protected function updateAnimation():void { var prevAnimation:String = _animation; if (_hurt) { _animation = "hurt"; } else if (_climbing) { _animation = _climbAnimation; } else if (!_onGround) { _animation = "jump"; } else if (_ducking) { _animation = "duck"; } else { var walkingSpeed:Number = getWalkingSpeed(); if (walkingSpeed < -acceleration) { _inverted = true; _animation = "walk"; } else if (walkingSpeed > acceleration) { _inverted = false; _animation = "walk"; } else { _animation = "idle"; } } if (prevAnimation != _animation) { onAnimationChange.dispatch(); } } } } |
You can find my zip.
And now, I will upgrade on Mac OS X Lion 🙂
Have you considered updating this to fit with the latest version of Citrus? I have started the conversion, but I am not as familiar with the engine as you are, I’m sure. For example, what happened to “gravity” It is no longer in the hero class and I’m not sure what has been implemented in it’s place.
Hey, this isn’t planned. The issue is it becomes very hard for newcomers to understand how the Hero class works. And I didn’t find a great way to make an hero with activable components even using the entity/component system.
Aymeric, I wanted to share with your readers my version of this code. I am using Citrus Engine V 3.1.6. Much of the above code is no longer valid for the new version. Here is my GameState.as file to show it in action http://pastebin.com/1iDZr6T3
Here is my new ladderHero class http://pastebin.com/pEvPvkd5
I really appreciate all the work you do on this project. Thanks
Hey David, that’s a nice code! Thank you for updated it!
Hello David and Aymeric
Do you guys know if there is a Nape version of a ladder?
thnx
No, I don’t think.