GAM666

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GAM666 Introduction To Game Programming
Basic 3D Using DirectX 9

• As of DirectX 8, DirectDraw (2D) and Direct3D
  (3D) have been combined into DirectX Graphics
  (still often called Direct3D, however)
• DirectX Graphics includes a library of 3D math
  helper functions, d3dx9math.h, the use of which
  is entirely optional but has gained wide
  acceptance

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GAM666 Introduction To Game Programming
Basic 3D Using DirectX 9

• DirectX 9 COM Object Pointers
• LPDIRECT3D9 main Direct3D control object used
  to create others
• LPDIRECT3DDEVICE9 device onto which 3D is
  rendered
• LPDIRECT3DVERTEXBUFFER9 list of vertices
  describing a shape to be rendered
• LP3DXFONT font for rendering text onto a 3D
  scene

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GAM666 Introduction To Game Programming
Basic 3D Using DirectX 9

• Basic frame rendering logic
• Clear the display target's backbuffer using
  Direct3DDevice Clear()
• Call Direct3DDevice BeginScene()
• Render primitives shapes using Direct3DDevice
  DrawPrimitive() and text using Direct3DXFont
  DrawText()
• Call Direct3DDevice EndScene()
• Flip backbuffer to screen with Direct3DDevice
  Present()

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GAM666 Introduction To Game Programming
3D Setup

• Direct3DCreate9() to create Direct3D object
• Enumeration in DirectX Graphics is easier than in
  DirectDraw7 (no enumeration callback function
  needs to be supplied, rather call a query
  function in your own loop)
• Direct3D CreateDevice() to create Direct3DDevice
• Direct3DDevice CreateVertexBuffer() to allocate
  vertex buffers
• D3DXCreateFont() to make 3D font

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GAM666 Introduction To Game Programming
Critical d3dx9math.h data types

• D3DXVECTOR3 x, y and z coordinates for a 3D
  point or vector (context determines which)
• D3DXMATRIX 4x4 3D transformation matrix
• There are many D3DX functions to create or
  manipulate these
• Visit http//gpwiki.org/index.php/3DMatrix_Math
  to review basics of 3D vectors and matrix
  arithmetic

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GAM666 Introduction To Game Programming
Fixed Function Transformation Pipeline

• Direct3D has us specify 3 transformation matrices
  (each vertex is transformed by all three, in
  turn, before it is rendered)
• World matrix moves a vertex from its specified
  coordinates to somewhere else
• View matrix moves a vertex so it will be as if
  we were looking from a particular viewpoint (with
  increasing Z coordinates in front of us)
• Projection matrix moves a vertex so that if we
  ignore the Z coordinate (2D projection),
  reasonable perspective will be apparent

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GAM666 Introduction To Game Programming
Fixed Function Transformation Pipeline

• Use Direct3DDevice SetTransform() to change one
  of the transformation matrices
• The world matrix is changed whenever we have a
  primitive to render that should not be moved to
  where the current world matrix would move it
  (typically, just before rendering each
  relocatable primitive)
• The view matrix is changed whenever we want the
  camera or viewpoint to change, typically with
  each frame as the user moves around
• The projection matrix is changed whenever we want
  to change the perspective or clipping, typically
  only once at the beginning

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GAM666 Introduction To Game Programming
Flexible Vertex Formats (FVF)

• When a vertex buffer is created, there is some
  flexibility in specifying exactly what data will
  be supplied for each vertex of a primitive (e.g.
  with a texture you need to supply texture
  coordinates for each vertex, but with no texture
  you might want to specify a colour for each
  vertex)
• The D3DFVF_ flags identify which pieces of data
  you'll be using, e.g.
• D3DFVF_XYZ means you want XYZ coordinates (almost
  always want this)
• D3DFVF_DIFFUSE means you want to specify a
  diffuse colour (sometimes want)

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GAM666 Introduction To Game Programming
Flexible Vertex Formats (FVF)

• Although FVF flags are combined with bitwise or
  () - so the order they are specified in doesn't
  matter - there IS an order in which the matching
  data will appear in the vertex buffer
• Use Vertex Formats in Visual Studio help to see
  the order the data will appear in the vertex
  buffer when specific vertex flags are used
• Use Direct3DDevice SetFVF() to specify what
  vertex format you are about to use

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GAM666 Introduction To Game Programming
Vertex Buffer Primitive Types

• D3DPT_POINTLIST list of separate points
• D3DPT_LINELIST list of line segments, 2
  vertices per segment
• D3DPT_LINESTRIP list of joined line segments, 2
  vertices for first, 1 for each thereafter
• D3DPT_TRIANGLELIST list of triangles, 3
  vertices per triangle
• D3DPT_TRIANGLEFAN list of triangles sharing a
  common starting point, 3 vertices for the first,
  1 for each thereafter
• D3DPT_TRIANGLESTRIP list of triangles, each
  sharing two points with the next, 3 vertices for
  the first, 1 for each thereafter

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GAM666 Introduction To Game Programming
Using Vertex Buffers

• Since vertex buffers may live on the video card
  or elsewhere where shared access may be a
  problem, you must lock a vertex buffer area
  before you update it, and unlock it when you are
  done
• Don't update vertex buffers needlessly, as it is
  potentially slow
• Use Direct3DDevice SetStreamSource() to identify
  which vertex buffer to use
• Use Direct3DDevice DrawPrimitive() to render a
  primitive from the current vertex buffer,
  specifying the type of primitive and number of
  primitives.

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GAM666 Introduction To Game Programming
Other Considerations

• The Direct3DDevice will probably need to be
  Reset() if you regain focus after losing it, and
  the vertex buffers (and anything else that might
  have resided in video memory) may have to be
  refilled or reallocated
• Use Direct3DDevice SetRenderState() to turn
  features (such as lighting and alpha blending) on
  or off, or otherwise control them
• Note that most of the characteristics of the
  fixed function transformation pipeline are
  obsoleted by newer, but not universally
  available, shader technology double coverage is
  required for the near future