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Tock Tick - Running Interactive E-Learning Animations Backwards

Tock Tick - Running Interactive E-Learning Animations Backwards. Jeremy Jones Dept. Computer Science Trinity College Dublin 2 Ireland. Overview. Initial motivation for Vivio Some example Vivio animations How does it work? Conclusions http://cs.tcd.ie/Jeremy.Jones/vivio

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Tock Tick - Running Interactive E-Learning Animations Backwards

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  1. Tock Tick - Running Interactive E-LearningAnimations Backwards Jeremy Jones Dept. Computer Science Trinity College Dublin 2 Ireland

  2. Overview • Initial motivation for Vivio • Some example Vivio animations • How does it work? • Conclusions • http://cs.tcd.ie/Jeremy.Jones/vivio • google: "jones vivio" + I feel lucky

  3. Initial Motivation • How best to explain the operation of cache-coherency protocols* to Computer Engineering students? • "I hear and I forget, I see and I remember, I do and I understand" [Confucius] • Envisaged some 2D web based interactive reversible animations to complement lectures • Students can use animations outside of lectures • Engage students, encourage active learning & critical thinking and consequently improve learning outcomes • Think before developing an interactive animation – NOT always appropriate *IEEE/ACM Computing Curricula 2001 section AR7 core

  4. Example Vivio Animations • may be embedded in a PowerPoint presentation, … [image rather than Vivio ActiveX control] • but easier to demonstrate inside a browser

  5. Animation Characteristics • interactive • scalable • reversible • web based • parallel • smooth animation • control animation speed (via mouse wheel) • single step forward and backwards • snap forward and backwards to key frames • standard hardware

  6. How can such animations be created? • interactive→ execution of an underlying program • reversible→ need to be able to execute program backwards (or give the appearance thereof) • very time consuming with existing technologies such as Java, Flash, SVG, ...

  7. Vivio • A programming language / model that provides an appropriate level of abstraction for describing E-Learning animations • An efficient runtime which handles the low level detail e.g. repainting the screen and playing animations in reverse

  8. Vivio IDE Viviosource code compiler vcode ActiveX player* (runtime) * may be hosted in a webpage, Word, PowerPoint, … How does it work? • Vivio source code compiled and stored as compressed vcode files (most examples less than 4K) • ActiveX player downloads the vcode, JIT compiles it into x86 machine code and then executes the generated code • Runtime only for Windows and x86 (so far!)

  9. Vivio Language Basics • normal • int, real, string, class • arrays, associative arrays • functions, while, for, … • animation specific • graphical objects (rectangles, ellipse, polygon, …) • groups, layers • animation clock • animated functions • fork(…)

  10. tick n+1 tick n+2 tick 0 tick 1 tick n x x x x r r x r x x r Event Driven / Event Q • animation clock @ t ticks per second (tps) • on each tick execute attached event code (x) and then… • render changes (r) • executed code can add events to the eventQ • typical render time >> execute time • aggressive code to minimise rendered screen area • no point rendering at rates > 100 tps

  11. Animated Functions • r = Rectangle(…..)r.setpos(x, y, steps, interval, wait) • setpos(…) sets position of r in steps steps with interval ticks between each step (linear interpolation from current position) • if wait = 1 execution waits until animation completes, otherwise execution continues immediately to the next statement • r.setpos(x, y) ≡ r.setpos(x, y, 0, 0, 0) • most functions, where it makes sense, exist in animated form • consider an example

  12. Running Backwards 1 tick 0 tick n animate forward at normal speed save state(SS) tick n-1 • animate forward at normal speed • wish to go back one tick • NB. state saved at tick = 0 [in reality state saved when each object changes for the first time]

  13. tick n tick 0 tick n-1 SS SS SS SS Running Backwards 2 • restore saved state at tick = 0 • fast forward by re-executing all events until tick n-1 • save state at regular intervals – every t ticks or t ms of "execution" time • render changes

  14. Running Backwards 3 tick n tick 0 tick n-1 tick n-2 SS SS SS SS • restore last saved state • fast forward by re-executing events until tick n-2 • render changes

  15. tick = 5000 tick = 4000 tick = 1000 tick = 0 state state state state Saving State 1 • incremental state saving (snapshots) • save changes only • technique also applied to non graphical objects graphical object created tick = 0 last updated tick = 0 current state rendered state snapshots

  16. Saving State 2 tick n tick 0 tick n-1 4 sub intervals SS SS 3t+3t/4 3t+t/4 0 t 2t 3t 3t+t/2 • reduce "execution" time by saving state more frequently and by saving state more frequently closer to target tick (t/N) • set save state parameters at runtime setSSParameters(tickOrMS, interval, nsubintervals) • could use an alternative strategy e.g. binary

  17. redraw region going forward tick n to tick n+1 redraw region going backwards from tick n to tick n-1 Playing Forward vs Backwards • same screen area rendered whether going forward or backwards – hence equal render times (not quite so easy to implement!) • more time spent in "execution" phase when playing backwards (set by frequency of state saves)

  18. Some Performance Measurements 1 • Vivio IDE instrumented to collect real time statistics using the Intel x86 hardware time stamp counter • measurements collected on a DELL Inspiron 8100 laptop with 1.13GHz mobile Pentium III and 256K DRAM (N.B. SpeedStep technology) • "avg exe (ms)" - everything apart from render time (i.e. executing event code, saving/restoring state, ...) • all animations displayed in an 800x600 32 bits per pixel window and run at 100 ticks/sec • save state every 1024 ticks with 0 subintervals except DLX every 512 ticks with 8 sub intervals • Note the "identical" render times playing forwards and backwards

  19. Some Performance Measurements 2 • Vivio IDE instrumented to collect real time statistics using the Intel x86 hardware time stamp counter • measurements collected on a DELL Dimension 8300 with 3.00GHz Pentium 4, 1GB DRAM and NVidia GeForce Fx 5200 graphics card • "avg exe (ms)" - everything apart from render time (i.e. executing event code, saving/restoring state, ...) • all animations displayed in an 800x600 32 bits per pixel window and run at 100 ticks/sec • saving state every 1024 ticks with 0 subintervals except DLX every 512ticks with 8 sub intervals • Note the "identical" render times playing forwards and backwards

  20. Some Performance Measurements 3 • "avg exe" time vs save state parameters for DLX/MIPS animation • conditions as per previous slide

  21. Conclusions • How frequently are the Vivio animations used? • installation/portability issues • Are the animations beneficial educationally? • survey results • How long does it take to create an animation? • took 3 months for Edsko De Vries (JS BA) to create the MIPS/DLX animation • What next?

  22. Thank you for listening. Any Questions?

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