问题
I want to show a triangle strip when user swap finger on screen. I am not sure how to do it with AndEngine, using particle system or using sprites or using Triangle Strip algo...
I haven't wrote any code because I am struck that what to do. I am uploading an image please share your ideas.
Update
someone has done this in Iphone but unfortunately I am unfamiliar with language syntax please help me in understanding algo of this code https://github.com/hiepnd/CCBlade
**Effect I want **
Complete Android Project Download
http://www.andengine.org/forums/resources/complete-runnable-project/1301
I have done this code but could not get the desired effect...
package org.az.algo.examples;
import javax.microedition.khronos.opengles.GL10;
import org.anddev.andengine.engine.Engine;
import org.anddev.andengine.engine.camera.Camera;
import org.anddev.andengine.engine.options.EngineOptions;
import org.anddev.andengine.engine.options.EngineOptions.ScreenOrientation;
import org.anddev.andengine.engine.options.resolutionpolicy.RatioResolutionPolicy;
import org.anddev.andengine.entity.particle.ParticleSystem;
import org.anddev.andengine.entity.particle.emitter.RectangleParticleEmitter;
import org.anddev.andengine.entity.particle.initializer.AlphaInitializer;
import org.anddev.andengine.entity.particle.initializer.ColorInitializer;
import org.anddev.andengine.entity.particle.initializer.GravityInitializer;
import org.anddev.andengine.entity.particle.initializer.RotationInitializer;
import org.anddev.andengine.entity.particle.modifier.AlphaModifier;
import org.anddev.andengine.entity.particle.modifier.ColorModifier;
import org.anddev.andengine.entity.particle.modifier.ExpireModifier;
import org.anddev.andengine.entity.scene.Scene;
import org.anddev.andengine.entity.scene.Scene.IOnSceneTouchListener;
import org.anddev.andengine.entity.sprite.Sprite;
import org.anddev.andengine.entity.util.FPSLogger;
import org.anddev.andengine.input.touch.TouchEvent;
import org.anddev.andengine.opengl.texture.TextureOptions;
import org.anddev.andengine.opengl.texture.atlas.bitmap.BitmapTextureAtlas;
import org.anddev.andengine.opengl.texture.atlas.bitmap.BitmapTextureAtlasTextureRegionFactory;
import org.anddev.andengine.opengl.texture.region.TextureRegion;
import android.view.ViewGroup.MarginLayoutParams;
import android.widget.Toast;
public class ParticleSystemSimpleExample extends BaseExample {
// ===========================================================
// Constants
// ===========================================================
private static final int CAMERA_WIDTH = 720;
private static final int CAMERA_HEIGHT = 480;
// ===========================================================
// Fields
// ===========================================================
private Camera mCamera;
private BitmapTextureAtlas mBitmapTextureAtlas;
private TextureRegion mParticleTextureRegion;
private BitmapTextureAtlas mBitmapTextureAtlasStreak;
private TextureRegion mStreadTextureRegion;
private Sprite[] mSprite = new Sprite[20];
private int mIndex = 0;
// ===========================================================
// Constructors
// ===========================================================
// ===========================================================
// Getter & Setter
// ===========================================================
// ===========================================================
// Methods for/from SuperClass/Interfaces
// ===========================================================
@Override
public Engine onLoadEngine() {
Toast.makeText(this, "Touch the screen to move the particlesystem.", Toast.LENGTH_LONG).show();
this.mCamera = new Camera(0, 0, CAMERA_WIDTH, CAMERA_HEIGHT);
return new Engine(new EngineOptions(true, ScreenOrientation.LANDSCAPE, new RatioResolutionPolicy(CAMERA_WIDTH, CAMERA_HEIGHT), this.mCamera));
}
@Override
public void onLoadResources() {
this.mBitmapTextureAtlas = new BitmapTextureAtlas(32, 32, TextureOptions.BILINEAR_PREMULTIPLYALPHA);
this.mParticleTextureRegion = BitmapTextureAtlasTextureRegionFactory.createFromAsset(this.mBitmapTextureAtlas, this, "gfx/particle_point.png", 0, 0);
this.mBitmapTextureAtlasStreak = new BitmapTextureAtlas(128, 16, TextureOptions.BILINEAR_PREMULTIPLYALPHA);
this.mStreadTextureRegion = BitmapTextureAtlasTextureRegionFactory.createFromAsset(this.mBitmapTextureAtlasStreak, this, "gfx/streak1.png", 0, 0);
this.mEngine.getTextureManager().loadTextures(this.mBitmapTextureAtlas, this.mBitmapTextureAtlasStreak);
}
@Override
public Scene onLoadScene() {
this.mEngine.registerUpdateHandler(new FPSLogger());
final Scene scene = new Scene();
// final CircleOutlineParticleEmitter particleEmitter = new CircleOutlineParticleEmitter(CAMERA_WIDTH * 0.5f, CAMERA_HEIGHT * 0.5f + 20, 80);
final RectangleParticleEmitter particleEmitter = new RectangleParticleEmitter(CAMERA_WIDTH * 0.5f, CAMERA_HEIGHT * 0.5f, 5f,5f);
// final PointParticleEmitter particleEmitter = new PointParticleEmitter(10, 10);
final ParticleSystem particleSystem = new ParticleSystem(particleEmitter, 100, 100, 1000, this.mParticleTextureRegion);
particleSystem.setParticlesSpawnEnabled(false);
scene.setOnSceneTouchListener(new IOnSceneTouchListener() {
@Override
public boolean onSceneTouchEvent(final Scene pScene, final TouchEvent pSceneTouchEvent) {
if(pSceneTouchEvent.getAction() == TouchEvent.ACTION_MOVE){
particleSystem.setParticlesSpawnEnabled(true);
particleEmitter.setCenter(pSceneTouchEvent.getX(), pSceneTouchEvent.getY());
mSprite[getIndex()].setPosition(pSceneTouchEvent.getX(), pSceneTouchEvent.getY());
mSprite[getIndex()].setVisible(true);
}else if (pSceneTouchEvent.getAction() == TouchEvent.ACTION_UP){
particleSystem.setParticlesSpawnEnabled(false);
hideAll();
}else if(pSceneTouchEvent.getAction() == TouchEvent.ACTION_DOWN){
particleSystem.reset();
}
return true;
}
});
particleSystem.addParticleInitializer(new ColorInitializer(1, 0, 0));
particleSystem.addParticleInitializer(new AlphaInitializer(0));
particleSystem.setBlendFunction(GL10.GL_SRC_ALPHA, GL10.GL_ONE);
// particleSystem.addParticleInitializer(new VelocityInitializer(-2, 2, -20, -10));
particleSystem.addParticleInitializer(new GravityInitializer());
// particleSystem.addParticleModifier(new ScaleModifier(0.5f, 1.0f, 0, 1.5f));
particleSystem.addParticleModifier(new ColorModifier(1, 1, 0, 0.5f, 0, 0, 0, 3));
particleSystem.addParticleModifier(new ColorModifier(1, 1, 0.5f, 1, 0, 1, 4, 6));
particleSystem.addParticleModifier(new AlphaModifier(0, 1, 0, 0.5f));
particleSystem.addParticleModifier(new AlphaModifier(1, 0, 2.5f, 3.5f));
particleSystem.addParticleModifier(new ExpireModifier(6, 6f));
scene.attachChild(particleSystem);
for(int i = 0; i < mSprite.length; i++){
mSprite[i] = new Sprite(-20, 0, mStreadTextureRegion);
mSprite[i].setVisible(false);
scene.attachChild(mSprite[i]);
}
return scene;
}
@Override
public void onLoadComplete() {
}
private int getIndex(){
if(mIndex >= mSprite.length -1){
mIndex = 0;
}
System.out.println("Index ........ "+mIndex);
return mIndex++;
}
private void hideAll(){
for(int i = 0; i<mSprite.length; i++){
mSprite[i].setVisible(false);
mSprite[i].setPosition(-CAMERA_WIDTH, 0);
}
}
// ===========================================================
// Methods
// ===========================================================
// ===========================================================
// Inner and Anonymous Classes
// ===========================================================
}
image I used with this code is also attached
Updated
partial effect achieved.. but problem on fast swiping.. all complete projects are uploaded here http://www.andengine.org/forums/post31772.html#p31772
回答1:
Here is a solution in LibGDX. It uses GL_TRIANGLE_STRIP.
https://github.com/mattdesl/lwjgl-basics/wiki/LibGDX-Finger-Swipe
The final solution uses two triangle strips and a custom texCoord attribute, allowing for us to use a lookup texture to achieve fake (but efficient) anti-aliasing. A more efficient/flexible anti-aliasing would use shaders and a single triangle strip. Use vertex attribute -1.0 for the top and 1.0 for the bottom edge of your swipe, and 1.0 for the tips. Then in the frag shader, use abs() -- so 0.0 means "center" and 1.0 means "edge."
Something like this:
color.a *= smoothstep(0.0, 2./thickness, 1.0-abs(vTexCoord.t));
来源：https://stackoverflow.com/questions/9698997/add-visual-below-finger-swipe-triangle-strip-like-fruit-ninja-andengine