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Introduction to Demoscene: Origins, Demoparties, and Classic Works

Explore the world of Demoscene, a fusion of art, music, and design in the form of jaw-dropping audiovisual effects created by passionate programmers. Learn about the history, origins, and evolution of Demos, as well as the iconic demoparties and classic works in Demoscene history.

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Introduction to Demoscene: Origins, Demoparties, and Classic Works

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  1. Presentation Title Demos and Real-time Computer Graphics First and Last Name Presenters Title Ng Chu Ming Alumni, Computer Graphics Research Lab

  2. Overview of Talk • Introduction to Demos • Origins of the Demoscene • Demoparties • Classic works • Different type of demos • Tricks and Techniques • Conclusion

  3. Introduction to DemosceneDemos : What are they? • Not Commercial or Game Demos! • Demos are… “the last bastion of passionate, crazed, enthusiast-only programming, crafted purely for the hell of it by inspired teenagers working entirely in their spare time. The teens create jaw-dropping audiovisual effects beyond the dreams of most multimedia designers. “ – Wired Magazine • New digital artform • Demos are a fusion of… • Art • Music • Design • Great Coding

  4. What are Demos?... Lets see…..

  5. Origins of the DemosceneDemos : How it all started… • Started in early 1980s due to software crackers • Cracker signature • Originated from ‘crack screens’… • From text… • To splash screens… • 2D animation… • … finally 3D animated effects and music • Eventually, many cracker groups started to release intro-like programs separately

  6. Origins of the DemosceneDemos : Today, in the state of the art… • 3D realtime ray tracing • Procedural Textures • Multiple Effects and transitions • Executable compression • Design and storyboarding

  7. Demo PartiesDemos : the now worldwide phenomenon… • Assembly ’06 (Helsinki, Finland) • Mother of all demo parties • The very first and longest running for 15 years • Sponsored by big names like • EA, Microsoft, AMD • Creative, ATI, Nokia, ASUS • Now a worldwide phenomenen • A Demoparty in almost every continent/country • The Party (Denmark), Breakpoint (Germany), The Gathering (Norway)… • 33 demo competitions over 23 Countries… • Even Singapore had one, The Scene in 1996

  8. Demo Show case: Classic and defining works … in DemoScene history.

  9. Classic and Defining works 2nd Reality by Future Crew • Produced and presented at Assembly 1993 • But… What is it like in 1993? • 386 PCs running DOS • 16bit. 64k limit. • NO OpenGL/Direct3D etc!

  10. Classic and Defining works 2nd Reality by Future Crew • Till today, it is still considered the greatest demo ever produced • Listed by Slashdot.org as Top 10 hacks of all time, alongside • Mars Pathfinder • Ken Thompson's "cc hack“ • Perl • The Apollo 13 Mission Rescue • 2nd Reality facts • Coded in FULL Assembly language • Dolby Surround • And group members were just 18-20 years old!

  11. 2nd Reality. Play DVD here

  12. Types of Demos… 4kb, 64kb, Full fledged demos…

  13. Types of Demos4 Kilobyte Intros • Yes, 4096 bytes. • Equivalent to… • 512 chars of text… • What it means… • No APIs to call • Code _EVERYTHING_ yourself, down to the last plotpixel • Alright… Just how small is 4Kb!?

  14. Types of Demos4 Kilobyte Intros • Okay… Lets take a look at…

  15. Types of Demos4 Kilobyte Intros • Yes, 4096 bytes. • Equivalent to… • 512 chars of text… • Alright… Just how small is 4Kb!? • Ok… Fine. So, What can you do in 4Kb?

  16. Types of Demos64 Kilobyte Intros • What can be done in 64Kb? • Well, this is what all of us do.....

  17. Types of Demos64 Kilobyte Intros • What can be done in 64Kb? • But you can really have, • Procedural geometry • Music • Textures • And even realtime raytracing with adaptive subsampling…

  18. Types of DemosFull fledged demo (> 1MB in size) • Well, anything goes here. • Lets check out one of the winning entries in Assembly 2006

  19. Types of DemosOther weird, strange, crazy, but cool stuff. • 256 bytes competition • Raytracer in 256 bytes • Text Mode demo competition • Textmode? You must be kidding me… • Hugi Size Coding competition • How small can nibbles get? • Ans : 48 bytes!

  20. Tricks and Techniques Assembly… fixed point math… speed hacks… taylor series approximations

  21. Tricks and TechniquesSize optimization… • Assembly language • There’s no running from it • Know the instruction set sizes • Be aware of processor arch. • 3 Levels in which the size problem is approached • Algorithmic tweaks • Compiler tweaks • OS tweaks

  22. Tricks and TechniquesSize optimization : Algorithmics… • Basically, think of ways to generate things on the fly • Procedural textures, procedural music, code, etc… • Simple example : • The texture on the right is 256x256, with 0-255 in colour [grey scale]. • Even as a .jpg [with compression] it takes a total of 6KB to store. This is larger than many intro’s! • An un-optimized procedural algo:for(y=0;y < 256;y++) for(x=0;x < 256; x++) height_value=(1-(sqrt(((x-128)*(x-128))+((y- 128)*(y-128)))/128))*255; • Note – even without code size optimizations, its <200 bytes in a basic C compiler – a 15 times improvement! • This is only a small example – you need to think algorithmically about, textures, geometry, music, and code!

  23. Tricks and TechniquesSize optimization : Compiler tools • Going one level down to language tools and selection • The principle is… • Don’t take what’s thrown to you out of the box • Assembly • Offers the most flexibility and options to push limits • Use of features in ways they weren’t first designed (more on that later) • C++ • Know everything about your compiler • Linker options, pragmas, etc…

  24. Tricks and TechniquesSize optimization : Compiler tools • C++ example • #include <windows.h> __stdcall WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) {MessageBox(0,“Silly example",“test!",MB_OK); return 0; } • This example, when compiled with “default” VC++ options results in a 24 KB EXE! 

  25. Tricks and TechniquesSize optimization : Compiler tools • Lets tweak it! • The same program, altered just a little bit…. #pragma comment(linker,"/ENTRY:main")#pragma comment(linker,"/MERGE:.rdata=.data")#pragma comment(linker,"/MERGE:.text=.data")#pragma comment(linker,"/IGNORE:4078")#pragma comment(linker,"/OPT:NOWIN98")#include <windows.h>void main(){MessageBox(0,"test","test",MB_OK);} • Becomes 1KB in size!

  26. Tricks and TechniquesSize optimization : Compiler tools • Err… So what the hell did you do? • Cut out the “fluff” that the compiler includes by default: • Microsoft Visual C++ Runtime Library • 4kb section alignment [not required] • Merged sections in the exe: • .text (default code section), • .rdata (default read-only data section) • .data (initial data section)

  27. Tricks and TechniquesSize optimization : OS Tweaks… • Going another level deeper… OS limitations! • This deals with OS limitations, or what a “executable” file is on that Operating system • Win32 programs have a lot of extra “fluff” in them, that you don’t need • Now…. MS-DOS had a light program. It supports 2 types of programs: • .COM files - limited to 64kb, but no headers! • .EXE files - for large exe • Coders started using executable packers. • Basically, compressing the exes • Still not enough! • Pack Exe files in COM files • Pack .CAB files • A lot of details here… (Omitted)

  28. Tricks and TechniquesOptimizing for speed : Processor level… • Again a wide spectrum art • How optimized your code is influence what you can put on your screen. • Knowledge of processor instruction sets and arch. Eg, • Use of lea instruction to do muls faster • xor eax, eax is faster than mov eax, 0 • Address generation interlocks (AGI) • It takes one clock cycle to calculate the address needed by an instruction which accesses memory • But if the address depends on result of an instruction in the preceding clock cycle, you have to wait an extra clock cycle => AGI • Eg. • ADD EBX,4 • MOV EAX,[EBX] ; AGI pipeline stall • Solution? Interleave instructions in between… • ADD EBX,4 • XOR ECX, ECX • MOV EAX,[EBX] ; No AGI stall

  29. Tricks and TechniquesOptimizing for speed : Algorithms… • Going one level up… Algorithms. • Numerical methods • Better algorithms to approximate calculations • Clever hacks • From the very simple, • Avoid multiplications/divisions • Use look up tables • To the more involved… • Using Taylor series to approx sqrt() • John Carmack’s famous Inverse Sqrt hack

  30. Tricks and TechniquesOptimizing for speed : Effect Hacks • Find more clever ways to suspend your disbelief! • Simple Example… Simulating Fire! • Wow!… physically based simulation! But…. • It takes FOREVER!

  31. Tricks and TechniquesOptimizing for speed : Effects Hacks • Take a look at this demo • Nice, simple and Realtime! • And it was already possible 10 years ago! • How it was done… • Use Indexed Color Mode • Set up a nice palette • Plot new pixels and just smooth the image • Evolve image using flow field

  32. Tricks and TechniquesOptimizing for speed : Effects Hacks • Take Heaven Seven by Exceed • Nobody thought realtime raytracing is possible in the year 2000 • But they made it possible with adaptive subsampling • And use heavily hand optimized assembly

  33. ConclusionWhat the scene has to offer… • For educators/academics : • Undergrads in today's Universities mostly don’t know the demo scene exists • The scene is an environment to foster students CG knowledge thru competition • Demo making is a good avenue to learn broad spectrum CS techniques • For example, creating a 64KB intro requires, • Cramming all code, models, textures, sound and all other data in a total of 64KB • This combines skills of, real-time performance, compression programming and content generation • For Commercial/Development : • Demo competitions are excellent place to recruit • Many game industry ppl used to be sceners

  34. Presentation Title Thank you First and Last Name Presenters Title

  35. Tricks and TechniquesOptimizing for speed : Algorithms… • Going one level up… Algorithms. • Numerical methods • Better algorithms to approximate calculations • Clever hacks • From the very simple, • Avoid multiplications/divisions • Use shift and add, eg in framebuffer look up. • Since framebuffers are contiguous block of memory, • pixel(x, y)=fb[y * x_res + x] // say x_res = 800 x 600 • Use shift and add! • pixel(x, y)=fb[y << 9 + y << 8 + y << 5 + x] • Even better… Lookup tables => pixel(x, y)=fb[ytable[y]+ x] • To the more involved… • Using Taylor series to approx sqrt(), John Carmack’s famous Inverse Sqrt hack

  36. Tricks and TechniquesSpeed hacks… • Fixed point math • Use Approximations! • Don’t Calculate what you don’t need to! • Use look up tables!

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