J2ME

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A presentation on DirectX
Alex Brill Emil Elazar Noam Monheit
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Contents

• What is DirectX?
• Historical Problem and its Solution
• Terminology
• Brief Components Description
• DirectX Versions History
• How DirectX really works?
• Architecture
• Direct3D in Details
• DirectX Alternatives
• OpenGL
• Advantages Disadvantages or Why DirectX?
• Installation SDK
• Demo Code Examples

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What is DirectX? (1)

• The Problem
• Dos vs. Windows 3.1 overhead.
• The PC architecture was never designed as a
  gaming platform.
• Machine can be VERY different from another.
• The will
• Windows a desirable platform for game
  development.
• Fast, low-level libraries to allow the developer
  maintain creative freedom over his games.
• Shift the burden of hardware support from the
  game developer to the hardware manufacture.
• Coexist peacefully with other Windows components.

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What is DirectX? (2)

• The Solution DirectX
• Direct access to Hardware
• A common standard which all games and multimedia
  applications could follow a common interface
  with whatever hardware is installed in the PC.
• Provides real-time multimedia and gaming services
  to programs graphics, sound, music, input (mouse
  / keyboard / joystick / etc), networking, and
  movie playback.
• Done by three Microsoft employeesCraig Eisler,
  Alex St. John, and Eric Engstrom.

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Whats DirectX? (3)

• There are two parts to DirectX the 'runtime' and
  the 'SDK' (Software Development Kit). Both are
  free the runtime is what players need to have on
  their computers in order to play a game, and the
  SDK is what a programmer needs to create games
  that use DirectX.
• Windows XP comes with the DirectX 8 runtime
  automatically installed it's a 4 MB download if
  players don't have it.
• The SDK, is over 100 MB to download, and it
  contains all the headers and libraries you need,
  plus documentation, samples, tutorials, and
  tools. Players don't need the SDK, only the
  runtime.
• Most games for Windows nowadays use DirectX in
  some form or another it is also the technology
  which powers Microsoft's XBox.

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What is DirectX? (4)
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Terminology (1)

• API (application program interface)- Set of
  routines, protocols, and tools for building
  software applications. Saves the programmer from
  dealing with implementation.
• Driver- Program that controls a device. Acts like
  a translator between the device and programs that
  use the device.
• Each device has its own set of specialized
  commands that only its driver knows. In contrast,
  most programs access devices by using generic
  commands. The driver, therefore, accepts generic
  commands from a program and then translates them
  into specialized commands for the device.

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Terminology (2)

• Sound Card- Enables the computer to output sound
  through speakers connected to the board, record
  sound input from a microphone connected to the
  computer, and manipulate sound stored on a disk.
• Video Adapter- A board that plugs into a PC to
  give it display capabilities.
• Modern video adapters contain memory, so that
  the computer's RAM is not used for storing
  displays. In addition, most adapters have their
  own graphics coprocessor for performing graphics
  calculations. These adapters are often called
  graphics accelerators.

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Terminology (3)

• Graphics Accelerator- Type of video adapter that
  contains its own processor to boost performance
  levels.
• These processors are specialized for computing
  graphical transformations, so they achieve better
  results than the general-purpose CPU used by the
  computer.
• In addition, they free up the computer's CPU to
  execute other commands while the graphics
  accelerator is handling graphics computations.
• Other characteristics that differentiate
  graphics accelerators
• memory Amount of memory determines resolution
  and colors amount.
• Two types of memory-DRAM or video RAM (VRAM),
  which enables the video circuitry and the
  processor simultaneously access the memory.
• bus 1995 PCI bus, nowadays PCIExpress bus.
• register width The wider the register, the more
  data the processor can manipulate with each
  instruction. 64-bit accelerators are already
  becoming common, and we can expect 128-bit
  accelerators in the near future.

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Terminology (4)

• GDI- Graphical Device Interface, a Windows
  standard for representing graphical objects and
  transmitting them to output devices, such as
  monitors and printers.
• HEL, HAL, COM and more to be discussed later

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DirectX Components

• DirectX Graphics
• DirectDraw
• Direct3D
• DirectInput
• DirectPlay
• DirectAudio
• DirectSound
• DirectMusic
• DirectShow
• DirectSetup

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DirectX Components (1)

• DirectX Graphics
• DirectDraw- A software interface that provides
  direct access to display devices while
  maintaining compatibility with the GDI and for
  transferring video processing from a PC's CPU to
  the video adapter.
• The standard was first developed by Intel and
  called the Display Control Interface (DCI) and
  later supported by Microsoft.
• When the CPU is not busy, the GDI updates the
  video display. If the CPU is busy, the DCI driver
  allows an application to send update information
  directly to the video adapter.
• Direct3D- An API for manipulating and displaying
  three-dimensional objects. Developed by
  Microsoft, Direct3D provides programmers with a
  way to develop 3-D programs that can use whatever
  graphics acceleration device is installed in the
  machine. Virtually all 3-D accelerator cards for
  PCs support Direct3D.
• Another 3-D standard offering similar
  functionality is OpenGL.

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DirectX Components (2)

• DirectInput- Enables an application to retrieve
  data from input devices even when the application
  is in the background.
• Also provides full support for any type of input
  device, as well as for force feedback.
• DirectPlay- A media-independent networking API
  that provides networking services at the
  transport protocol and session protocol levels.
  DirectPlay sessions can be run on TCP/IP
  networks, IPX networks, and over directly
  connected modems and serial cables.

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DirectX Components (3)

• DirectX Audio
• DirectSound- Enables the playing of sounds with
  very low latency and gives applications a high
  level of control over hardware resources.
• DirectMusic- In combination with DirectSound,
  DirectMusic provides a complete solution for
  playing music and sound effects in games and
  other applications.

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DirectX Components (4)

• DirectShow- An architecture for streaming media
  on a Windows platform. It provides high-quality
  capture and playback of multimedia streams.
  Screeen Saver, Camera..
• DirectSetup- Extremely simple library of
  functions for installing DirectX on a machine.
• It also provides a way to check the version of
  DirectX that is present.

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Versions (1)

• For each new version of DirectX, Microsoft
  updated the technology such that the new dll's
  can communicate with the hardware faster and more
  efficiently with minimum latency.
• Theyre trying to support the latest features of
  graphics and sound cards that come on the market.
• The architecture is updated so as to suit the
  needs of the day while maintaining backward
  compatibility.

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Versions (2)

• DirectX 1.0
• released on late 1995.
• DirectX 6
• 2 independent SDK's (DirectX SDK and DirectX
  Media SDK).
• DirectX 7
• DirectShow- the significant part of Media SDK,
  merged into the DirectX API and DirectX Media
  deprecated.
• DirectX 8
• DirectDraw and Direct3D merged into a single
  DirectX Graphics API for graphics programming.
• DirectSound and Direct Music merged together as
  DirectX Audio for sound programming.
• Programmable Pixel Shader and Vertex Shader
  introduced.

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Versions (3)

• DirectX 9
• HLSL (High Level Shader Language), a powerful new
  programming model that offers the easiest to use
  graphics creation toolset for developers
  introduced.
• DirectX10 Part of Windows Vista.
• No backward compatibly except via a software
  layer.
• Much faster DLLs
• Departure from driver model of DirectX 9.0, with
  the addition of a scheduler and memory
  virtualization system.
• DirectX 10 will forego the current DirectX
  practice of using "capability bits" to indicate
  which features are active on the current
  hardware. Instead, DirectX 10 will define a
  minimum standard of hardware capabilities which
  must be supported for a display system to be
  "DirectX 10 compatible".

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Versions (4)

• Which version of DirectX do various versions of
  Windows come with?
• 95 None95B DX 3(Supports up to
  DX8)NT DX2NT w/SP 4 DX398 DX598SE DX6ME
  DX7.12000 DX7.1XP DX8.1

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Screenshots
Wolfenstein (3D Realms 1992 gt no HAL)
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DirectX in details
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DirectX COM objects

• DirectX is a set of APIs, available as COM
  objects.
• Component Object Model (COM) is a Microsoft
  platform for software componentry introduced by
  Microsoft in 1993. It is used to enable
  cross-application communication and dynamic
  object creation in any programming language that
  supports the technology.
• All DirectX Interfaces inherit from IUnknown and
  are COM compliant.
• IUnKnown
• AddRef()
• Release()
• QueryInterface()
• Reference counting

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Backward Compatibility (1)

• COM allows Microsoft release an enhanced set of
  DirectX components that are completely compatible
  with earlier versions of DirectX.
• With COMs independence of a programming
  language, developers are free to choose whatever
  COM compliant language and development
  environment they wish.
• With COMs programming model, the programmer is
  assured that even if the user upgrades or changes
  hardware configuration and DirectX drivers, the
  software will work without reconfiguration.

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Backward Compatibility (2)

• For example, even though DirectDraw was erased
  from the DirectX API components after DirectX 7
  even in DirectX9, you can access the old
  interfaces through a DirectDraw7 call.
• This backward compatibility plays a significant
  role in DirectX's position as a leading API, as
  it helps the applications written in older
  versions to still work smoothly in the newer
  versions.

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How it really works?

• DirectX provides the interface to access the
  advanced features of the display adapter, which
  are not provided in the standard Windows GDI
  graphics interface.
• It accesses the hardware abstraction layer in
  Windows directly.
• When DirectX was introduced, display adapter
  vendors were quick to develop DirectX drivers
  that would expose low-level functions of their
  hardware to the application.

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Architecture

• Each chip manufacturer, board producer, or OEM
  implements a HAL which implements only
  device-dependent code and performs no emulation.
• The HAL is implemented using 32-bit code with
  Microsoft Windows XP, Microsoft Windows NT, and
  Windows 2000. Windows 98 and Windows Millennium
  Edition (Windows Me) use a combination of 16-bit
  and 32-bit code.
• The HAL can be part of the display driver or a
  separate dynamic-link library (DLL) that
  communicates with the display driver through a
  private interface that the driver's creator
  defines.
• HAL is based around the hardware support, and is
  very fast but might not support everything

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Architecture

• When DirectX is initialized, it checks the
  hardware to see if the hardware supports certain
  capabilities. If the hardware does support a
  certain capability, then the HAL will be used to
  access that hardware function otherwise, the HEL
  will be used to emulate the capability through
  software.
• HEL bypasses the hardware and implements its own
  functionality.
• HEL uses no hardware acceleration. It uses the
  CPU, software, and normal system RAM. It is
  usually MUCH slower, but much less problematic

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Architecture
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3D - Graphics

• Rendering - the process of generating an image
  from a model, by means of a software program .

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3D - Graphics

• The Application is your game and is where you do
  any scene management and any tessellation of mesh
  etc.
• You then feed the graphics card with vertices and
  other data.
• The graphic card processes the vertices by
  transforming and lighting them using the matrices
  supplied by the application.
• The card then culls any invisible polygons and
  clips to the viewport.
• This transformed data is then rasterized and
  passes through the pixel operations
• The data is displayed.

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3D - Graphics
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Some terms

• Rasterisation - The task of taking a
  two-dimensional image described in a vector
  format and converting it into pixels or dots for
  output on a video display or printer.
• A tessellation (tiling) of
• the plane is a collection
• of plane figures that fill the
• plane with no overlaps and no gaps.
• A shader is a program used to determine the final
  surface properties of an object or image.

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Programmable Pipeline

• One of the most important new features in
• DirectX Graphics is the addition of a
• programmable pipeline.
• It provides an assembly language interface to the
  transformation and lighting hardware (vertex
  shader) and the pixel pipeline (pixel shader).
• This programmable pipeline gives the developer a
  lot more freedom to do things, which have never
  been seen in real time applications before.
• The shader code is loaded into the graphics card
  memory and plugged directly into the graphics
  pipeline. Shader code is in assembly however
  nowadays there are a number of higher level 'C'
  type languages that can be compiled down to the
  assembly and making them much easier to program.
• Microsoft have HLSL (High-Level Shading Language)
  for use with DirectX and OpenGL has the GLSL
  (OpenGL Shading Language).

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Programmable Pipeline

• When you push vertices through the pipeline, they
  need to be transformed and lit.
• This processing stage is known as TL.
• Hardware vertex processing means this is done in
  hardware, if hardware supports it
• Software vertex processing is done in software.
• The general practice is to try creating a
  Hardware TL device. If that fails try Mixed, and
  if that fails try Software. (If software fails,
  give up and exit with an error).

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DirectX - Conclusion

• DirectX gives multimedia applications greater
  access to advanced features of high-performance
  hardware such as 3D graphics acceleration chips
  and sound cards.
• It controls 2D graphics acceleration 
• Support for input devices joysticks / joy-pads,
  keyboards, mice, controls sound mixing and sound
  output on a vast range of audio
  hardware, controls networking and multiplayer
  gaming, and control over various multimedia
  streaming formats.

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DirectX Alternative (1)

• Open Graphics Library is a specification
  defining a cross-language cross-platform API
  for writing applications that produce 3D computer
  graphics (2D computer graphics as well). The
  interface consists of over 250 different function
  calls which can be used to draw complex
  three-dimensional scenes from simple primitives.

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DirectX Alternative (2)

• The OpenGL specification is overseen by the
  OpenGL Architecture Review Board (ARB), which was
  formed in 1992. The ARB consists of a set of
  companies with a vested interest in creating a
  consistent and widely available API.

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DirectX Alternative (3)

• OpenGL- platform Independent supported on
  Windows, Mac, Linux, and several other UNIX
  variants.
• Direct3D- only Windows.
• OpenGL- function oriented interface.
• Direct3D- object oriented interface.

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DirectX Alternative (4)

• Direct3D- updated very frequently (once a year)
  and supports the latest card features
  (Microsoft).
• OpenGL- takes some time to reach a new standard
  (open-standard and a community product, Silicon
  Graphics).
• Performance Equal performance!!

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Where do I start?

• If you're worried about which one to learn, and
  which one the pros use, the answer is that more
  often than not they'll use both.
• Apart from Direct3D, all the DirectX components
  can be used alongside OpenGL. If you want to use
  DirectInput for joystick input and OpenGL for
  your graphics, that's fine.

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Games(1)

• The 3D engine of the game Battlefield 1942 sits
  solidly on a DirectX 7 foundation.

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Games(2)

• Unreal Tournament 2003 uses a number of DirectX 8
  shader effects. As a result, the game's graphics
  look much better than that of older games, and
  the in-game world seems more alive.

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Games(3)

• FarCry can be considered the first game that
  makes consistent use of shaders. Thanks to
  DirectX 9, the surfaces look very realistic and
  react to changes in lighting.

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Further Reading - Web Resources

• General
• International Game Developers Assoc. -
  www.igda.org
• GamaSutra - www.gamasutra.com
• Game Developer - www.gamedev.net
• Direct X
• MSDN - www.msdn.com/directx
• Newsgroup - microsoft.public.win32.programmer.dire
  ctx.managed
• The Z Buffer - www.thezbuffer.com
• Tom Miller (main coder/designer) -
  blogs.msdn.com/tmiller

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Further Reading - DirectX Books
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The End