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libGDX: Simple Frame Animation
- 1. libGDX: Simple Anima0on Jussi Pohjolainen Tampere University of Applied Sciences
- 3. Framerate Indepence • Games run at same speed no ma6er the framerate • In slow computers; 30 fps, fast computers 60 fps – No need to go over 60 fps.. • Example – Fast computer, 60 fps, move object 1 px at a =me – Slow computer, 30 fps, move object 2 px at a =me – => constant speed no maNer the framerate! • The key to framerate indepence is delta-‐'me – Time in seconds since the last 0ck (last render() call) • 100 fps => 1/100 => 0.01 dt
- 4. Moving Object • At 30 fps vs 60 fps this object will move at different speeds – int speedX = 1; – batch.draw(texture, x += speedX, 0); • This will move the object at constant speed regardless of fps – int speedX = 60; – batch.draw(texture, x += speedX * deltaTime, 0); • If fps 60, deltaTime 60/1 = 0.0166 secs – x += 60 * 0.016666, x += 1 • If fps 30, deltaTime 30/1 = 0.0333 secs – x += 60 * 0.033333, x += 2
- 5. libGDX, delta and fps • Querying FPS – Gdx.graphics.getFramesPerSecond() • Querying Delta – Gdx.graphics.getDeltaTime()
- 6. Anima0on • Use Anima0on class – Animation walkAnimation = new Animation(frameDuration, frames); • Frame dura0on? 1 / 60 fps • Frames? – TextureRegion array • TextureRegion? – Part of texture
- 8. Split .png into TextureRegions walkSheet = new Texture(Gdx.files.internal(”image.png")); TextureRegion[][] tmp = TextureRegion.split( walkSheet, walkSheet.getWidth() / FRAME_COLS, walkSheet.getHeight() / FRAME_ROWS );
- 9. 2D array -‐> 1D private TextureRegion[] transformTo1D(TextureRegion[][] tmp) { TextureRegion [] walkFrames = new TextureRegion[FRAME_COLS * FRAME_ROWS]; int index = 0; for (int i = 0; i < FRAME_ROWS; i++) { for (int j = 0; j < FRAME_COLS; j++) { walkFrames[index++] = tmp[i][j]; } } return walkFrames; }
- 10. Rendering public void render() { // stateTime was initialized to 0.0f stateTime += Gdx.graphics.getDeltaTime(); // stateTime is used to calculate the next frame // frameDuration! currentFrame = walkAnimation.getKeyFrame(stateTime, true); spriteBatch.begin(); spriteBatch.draw(currentFrame, 150, 150); spriteBatch.end(); }
- 11. TIPS
- 12. Extend Sprites • For each Sprite in screen, create own class – class Monster extends Sprite • Add Monster aNributes like – speedX, speedY, sounds, … • If using anima0on (previous slides) you could create animate() method which is called from the game on every frame • When crea0ng the Sprite, remember to call also setRegion to set the ini0al region for the sprite