High Performance Java Swing Animation

David Wallace Croft2004-05-22

Presented to thePlano Java Users Group

Plano, TX

Copyright 2004 David Wallace Croft.This work is licensed under the Creative Commons Attribution License.

David Wallace Croft

● Founder and VP, Game Developers Java Users Group (www.GameJUG.org)

● Taught Java game programming at the Institute of Interactive Arts & Engineering at UTD

● Author of "Advanced Java Game Programming"(www.CroftSoft.com/library/books/ajgp/)

● Software Developer, NIST ATP "Peer-to-Peer Virtual Reality Learning Environments" research grant project, Whoola Inc.

Open Source

● All code presented today is Open Source● Code documented in detail in the book

"Advanced Java Game Programming"● Source code available for download from

www.CroftSoft.com/library/books/ajgp/● Public Domain multimedia files also available● This presentation archived on CroftSoft website

Performance Issues

● Clock resolution● Hardware acceleration● Repaint algorithm

Clock Resolution

● Need at least 24 fps for smooth animation● Period of less than 42 ms● System.currentTimeMillis()● Clock resolution 50 to 60 ms on some Windows● Swing Timer class limited to 20 fps● Possibly due to clock resolution?● Thread.sleep() within loop finer control

Animation Loop

● Phase 1: update sprite positions● Phase 2: repaint sprites at new positions● Phase 3: delay

LoopGovernor

● Slows animation loop down to desired frame rate● Too slow = jerky animation● Too fast = faster than monitor refresh, 100% CPU

Do not squander time, for that is the stuff life is made of. -- Benjamin Franklin

● FixedDelayLoopGovernor● SamplerLoopGovernor● WindowedLoopGovernor

Hardware Acceleration

● Hardware acceleration for images● Added to Java in version 1.4● Big difference in performance

Definitions

● VRAM = Video Random Access Memory● Blit = BLT = Block Line Transfer● Buffer = block of memory for image data● Pixel = picture element● Render = calculate and store pixel data● Primary surface = screen surface● Back buffer = offscreen image

Class Image

● Package java.awt● Holds pixel (picture element) data● Abstract superclass● Subclasses

– BufferedImage– VolatileImage

BufferedImage

● Quick and easy to modify pixel data● Pixel data not in video memory● Slow to transfer to video memory● Blitting● No hardware acceleration for drawing ops

VolatileImage

● Component.createVolatileImage(width,height)● Pixel data in video memory (VRAM)● Hardware acceleration for drawing ops● Video memory is volatile● Screen saver will invalidate● Must check and reload● boolean VolatileImage.contentsLost()

CompatibleImage

● GraphicsConfiguration.createCompatibleImage()● Pixel format conversion not needed● BufferedImage for pixel manipulation● VolatileImage cache for fast blitting● Caching mechanism validates volatile memory● Best for static images since cached● Caching algorithm out of your control

Transparency

● GraphicsConfiguration.createCompatibleImage (

width, height, transparency )● Transparency.OPAQUE● Transparency.BITMASK● Transparency.TRANSLUCENT● TRANSLUCENT not accelerated so slow● Transparency lost when copying to VolatileImage

Translucent Demo

● SpriteDemo fog option● Performance drops

Scaled BLT

● Graphics.drawImage ( x, y, width, height, null )● Slow● Solution = pre-scale

loadAutomaticImage()

● com.croftsoft.core.awt.image.ImageLib● Source code review

Repaint Algorithm

● Default algorithm in Swing bad for animation● Creates union of dirty rectangles● Slows down when rectangles far apart● Demonstration using Sprite

RepaintCollector

● Phase 1: Collects repaint requests● Phase 2: Delivers repaint requests● Coalesces requests for efficiency● Default algorithm in Swing bad for animation● SimpleRepaintCollector● BooleanRepaintCollector● CoalescingRepaintCollector

References

● Jeffrey Kesselman, Understanding the AWT Image Types

● Michael Martak, Full-Screen Exclusive Mode API

● Sun, High Performance Graphics● Sun, The VolatileImage API User Guide

Questions?

● Also ask via book discussion mailing list