没有美工的程序员，能够依赖的还有粒子系统。
这一章我们将使用libGDX的粒子系统线性插值以及其他的方法来增加一些特效。
你也可以使用自己编辑的粒子效果，比如这个粒子文件dust：http://files.cnblogs.com/mignet/particles.zip
这个灰尘的特效用在兔子头在地面跑的时候，啪啪的一溜烟。
线性插值可以让我们的摄像机在移动的时候更平滑。
当然，之前提到的背景上的山要实现视差移动效果也要实现。
白云会用随机的速度从右向左飘。
GUI的部分也要增加些效果比如掉了命，得了分等。
粒子系统通常用来模拟复杂的特效：比如fire, smoke, explosions等等.
ParticleEffect简介：
• start(): This starts the animation of the particle effect
• reset(): This resets and restarts the animation of the particle effect
• update(): This must be called to let the particle effect act in accordance to time
• draw(): This renders the particle effect at its current position
• allowCompletion(): This allows emitters to stop smoothly even if particle effects are set to play continuously
• setDuration(): This sets the overall duration the particle effect will run
• setPosition(): This sets the position to where it will be drawn
• setFlip(): This sets horizontal and vertical flip modes
• save(): This saves a particle effect with all its settings to a file
• load(): This loads a particle effect with all its settings from a saved file
• dispose(): This frees all resources allocated by the particle effect
粒子效果通常需要一个粒子发射器ParticleEmitter：
ParticleEffect effect = new ParticleEffect();
ParticleEmitter emitter = new ParticleEmitter();
effect.getEmitters().add(emitter);
emitter.setAdditive(true);
emitter.getDelay().setActive(true);
emitter.getDelay().setLow(0.5f);
// ... more code for emitter initialization ...
当然，不建议在代码里初始化例子发射器。因为发射器有20多个属性，要是在代码里初始化会很杂乱并且不容易维护。我们使用Libgdx的编辑器来编辑想要的粒子。
https://github.com/libgdx/libgdx/wiki/Particle-editor
我们来调个灰尘特效吧：
保存文件到CanyonBunny-android/assets/particles/dust.pfx
虽然并没有规定粒子文件要用什么文件后缀，但是我们统一叫pfx。记得把图片https://github.com/libgdx/libgdx/blob/master/extensions/gdx-tools/assets/particle.png
也保存到相同的文件夹。
首先在兔子头BunnyHead里添加代码：
public ParticleEffect dustParticles = new ParticleEffect();
public void init () {
...
// Power-ups
hasFeatherPowerup = false;
timeLeftFeatherPowerup = 0;
// Particles
dustParticles.load(Gdx.files.internal("particles/dust.pfx"),
Gdx.files.internal("particles"));
}
@Override
public void update (float deltaTime) {
super.update(deltaTime);
...
dustParticles.update(deltaTime);
}
@Override
public void render (SpriteBatch batch) {
TextureRegion reg = null;
// Draw Particles
dustParticles.draw(batch);
// Apply Skin Color
...
}让灰尘跟着兔子：
protected void updateMotionY(float deltaTime) {
switch (jumpState) {
case GROUNDED:
jumpState = JUMP_STATE.FALLING;
if (velocity.x != 0) {
dustParticles.setPosition(position.x + dimension.x / 2,
position.y);
dustParticles.start();
}
break;
。。。
if (jumpState != JUMP_STATE.GROUNDED){
dustParticles.allowCompletion();
super.updateMotionY(deltaTime);
}
}
｝ok，跑起..
接下来，让云飘起来：
private Cloud spawnCloud() {
Cloud cloud = new Cloud();
cloud.dimension.set(dimension);
// select random cloud image
cloud.setRegion(regClouds.random());
// position
Vector2 pos = new Vector2();
pos.x = length + 10; // position after end of level
pos.y += 1.75; // base position
// random additional position
pos.y += MathUtils.random(0.0f, 0.2f)
* (MathUtils.randomBoolean() ? 1 : -1);
cloud.position.set(pos);
// speed
Vector2 speed = new Vector2();
speed.x += 0.5f; // base speed
// random additional speed
speed.x += MathUtils.random(0.0f, 0.75f);
cloud.terminalVelocity.set(speed);
speed.x *= -1; // move left
cloud.velocity.set(speed);
return cloud;
}
@Override
public void update(float deltaTime) {
for (int i = clouds.size - 1; i >= 0; i--) {
Cloud cloud = clouds.get(i);
cloud.update(deltaTime);
if (cloud.position.x < -10) {
// cloud moved outside of world.
// destroy and spawn new cloud at end of level.
clouds.removeIndex(i);
clouds.add(spawnCloud());
}
}
}线性插值，让摄像机平滑移动到跟随的目标（Libgdx已经实现了lerp）CameraHelper：
private final float FOLLOW_SPEED = 4.0f;
public void update(float deltaTime) {
if (!hasTarget())
return;
position.lerp(target.position, FOLLOW_SPEED * deltaTime);
// Prevent camera from moving down too far
position.y = Math.max(-1f, position.y);
}让岩石浮在水面上Rocks：
private final float FLOAT_CYCLE_TIME = 2.0f;
private final float FLOAT_AMPLITUDE = 0.25f;
private float floatCycleTimeLeft;
private boolean floatingDownwards;
private Vector2 floatTargetPosition; private void init() {
dimension.set(1, 1.5f);
regEdge = Assets.instance.rock.edge;
regMiddle = Assets.instance.rock.middle;
// Start length of this rock
setLength(1); floatingDownwards = false;
floatCycleTimeLeft = MathUtils.random(0, FLOAT_CYCLE_TIME / 2);
floatTargetPosition = null;
} @Override
public void update(float deltaTime) {
super.update(deltaTime);
floatCycleTimeLeft -= deltaTime;
if (floatTargetPosition == null)
floatTargetPosition = new Vector2(position);
if (floatCycleTimeLeft <= 0) {
floatCycleTimeLeft = FLOAT_CYCLE_TIME;
floatingDownwards = !floatingDownwards;
floatTargetPosition.y += FLOAT_AMPLITUDE
* (floatingDownwards ? -1 : 1);
}
position.lerp(floatTargetPosition, deltaTime);
}
让山随着兔子视差Mountains：
public void updateScrollPosition(Vector2 camPosition) {
position.set(camPosition.x, position.y);
}
private void drawMountain(SpriteBatch batch, float offsetX, float offsetY,
float tintColor, float parallaxSpeedX) {
TextureRegion reg = null;
batch.setColor(tintColor, tintColor, tintColor, 1);
float xRel = dimension.x * offsetX;
float yRel = dimension.y * offsetY;
// mountains span the whole level
int mountainLength = 0;
mountainLength += MathUtils.ceil(length / (2 * dimension.x)
* (1 - parallaxSpeedX));
mountainLength += MathUtils.ceil(0.5f + offsetX);
for (int i = 0; i < mountainLength; i++) {
// mountain left
reg = regMountainLeft;
batch.draw(reg.getTexture(), origin.x + xRel + position.x
* parallaxSpeedX, origin.y + yRel + position.y, origin.x,
origin.y, dimension.x, dimension.y, scale.x, scale.y,
rotation, reg.getRegionX(), reg.getRegionY(),
reg.getRegionWidth(), reg.getRegionHeight(), false, false);
xRel += dimension.x;
// mountain right
reg = regMountainRight;
batch.draw(reg.getTexture(), origin.x + xRel + position.x
* parallaxSpeedX, origin.y + yRel + position.y, origin.x,
origin.y, dimension.x, dimension.y, scale.x, scale.y,
rotation, reg.getRegionX(), reg.getRegionY(),
reg.getRegionWidth(), reg.getRegionHeight(), false, false);
xRel += dimension.x;
}
// reset color to white
batch.setColor(1, 1, 1, 1);
}
@Override
public void render(SpriteBatch batch) {
// 80% distant mountains (dark gray)
drawMountain(batch, 0.5f, 0.5f, 0.5f, 0.8f);
// 50% distant mountains (gray)
drawMountain(batch, 0.25f, 0.25f, 0.7f, 0.5f);
// 30% distant mountains (light gray)
drawMountain(batch, 0.0f, 0.0f, 0.9f, 0.3f);
}把这个加到worldcontroller里：
public void update(float deltaTime) {
handleDebugInput(deltaTime);
if (isGameOver()) {
timeLeftGameOverDelay -= deltaTime;
if (timeLeftGameOverDelay < 0)
backToMenu();
} else {
handleInputGame(deltaTime);
}
level.update(deltaTime);
testCollisions();
cameraHelper.update(deltaTime);
if (!isGameOver() && isPlayerInWater()) {
lives--;
if (isGameOver())
timeLeftGameOverDelay = Constants.TIME_DELAY_GAME_OVER;
else
initLevel();
}
level.mountains.updateScrollPosition(cameraHelper.getPosition());
}现在，增加GUI的特效。
首先是掉了命：
在worldcontroller里加public float livesVisual;
private void init() {
Gdx.input.setInputProcessor(this);
cameraHelper = new CameraHelper();
lives = Constants.LIVES_START;
livesVisual = lives;
timeLeftGameOverDelay = 0;
initLevel();
}
public void update(float deltaTime) {
handleDebugInput(deltaTime);
if (isGameOver()) {
timeLeftGameOverDelay -= deltaTime;
if (timeLeftGameOverDelay < 0)
backToMenu();
} else {
handleInputGame(deltaTime);
}
level.update(deltaTime);
testCollisions();
cameraHelper.update(deltaTime);
if (!isGameOver() && isPlayerInWater()) {
lives--;
if (isGameOver())
timeLeftGameOverDelay = Constants.TIME_DELAY_GAME_OVER;
else
initLevel();
}
level.mountains.updateScrollPosition(cameraHelper.getPosition());
if (livesVisual > lives)
livesVisual = Math.max(lives, livesVisual - 1 * deltaTime);
}同时，在WorldRenderer里相应的修改：
private void renderGuiExtraLive(SpriteBatch batch) {
float x = cameraGUI.viewportWidth - 50 - Constants.LIVES_START * 50;
float y = -15;
for (int i = 0; i < Constants.LIVES_START; i++) {
if (worldController.lives <= i)
batch.setColor(0.5f, 0.5f, 0.5f, 0.5f);
batch.draw(Assets.instance.bunny.head, x + i * 50, y, 50, 50, 120,
100, 0.35f, -0.35f, 0);
batch.setColor(1, 1, 1, 1);
}
if (worldController.lives >= 0
&& worldController.livesVisual > worldController.lives) {
int i = worldController.lives;
float alphaColor = Math.max(0, worldController.livesVisual
- worldController.lives - 0.5f);
float alphaScale = 0.35f * (2 + worldController.lives - worldController.livesVisual) * 2;
float alphaRotate = -45 * alphaColor;
batch.setColor(1.0f, 0.7f, 0.7f, alphaColor);
batch.draw(Assets.instance.bunny.head, x + i * 50, y, 50, 50, 120,
100, alphaScale, -alphaScale, alphaRotate);
batch.setColor(1, 1, 1, 1);
}
}数字增涨效果：
WorldController增加：public float scoreVisual;在initLevel中添加scoreVisual = score;
在update的最后增加
if (scoreVisual < score)
scoreVisual = Math.min(score, scoreVisual+ 250 * deltaTime);
在WorldRenderer里修改：
private void renderGuiScore(SpriteBatch batch) {
float x = -15;
float y = -15;
float offsetX = 50;
float offsetY = 50;
if (worldController.scoreVisual < worldController.score) {
long shakeAlpha = System.currentTimeMillis() % 360;
float shakeDist = 1.5f;
offsetX += MathUtils.sinDeg(shakeAlpha * 2.2f) * shakeDist;
offsetY += MathUtils.sinDeg(shakeAlpha * 2.9f) * shakeDist;
}
batch.draw(Assets.instance.goldCoin.goldCoin, x, y, offsetX, offsetY,
100, 100, 0.35f, -0.35f, 0);
Assets.instance.fonts.defaultBig.draw(batch, ""
+ (int) worldController.scoreVisual, x + 75, y + 37);
}在下一章，我们将使用转场动画来平滑的过渡场景