GAM666 – Introduction To Game Programming

1. 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

2. 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

3. 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()

4. 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

5. 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/3D:Matrix_Math to review basics of 3D vectors and matrix arithmetic

6. 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

7. 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

8. 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)

9. 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

10. 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

11. 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.

12. 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