Direct3D Basics

Direct3D Basics
with Examples in C/C++

Prof. David Bernstein
James Madison University

Computer Science Department

bernstdh@jmu.edu

The Direct3D Architecture

Primitives:
- Raw vertices are stored in vertex memory buffers
- Geometric primitives (points, lines, triangles, and polygons) reference the raw vertices
The Pipeline:
- Tessellation Unit
- Vertex Processing Unit
- Geometry Processing Unit (clipping, culling and rasterization)
- Pixel Processor

Direct3D Concepts

Device:
- The rendering component
- Contains a transformation module, lighting module, and rasterization module
- Created using DXUT or
  HRESULT IDirect3D9::CreateDevice(UINT adapter, D3DDEVTYPE type, HWND window, DWORD flags, D3DPRESENT_PARAMETERS* params, IDirect3DDevice9** returnedDevice)
Device Types:
- Hardware accelerated rasterization; both hardware and software vertex processing (D3DDEVTYPE_HAL)
- Reference device used for debugging that includes every feature (D3DDEVTYPE_REF)

Direct3D Concepts (cont.)

Processing Vertex Data:
- D3DCREATE_SOFTWARE_VERTEXPROCESSING
- D3DCREATE_HARDWARE_VERTEXPROCESSING
- D3DCREATE_MIXED_VERTEXPROCESSING
Render States:
- Alpha Blending State
- Ambient Lighting State
- Antialiasing State
- Depth Buffering State
- Fog State
- Lighting State
- Outline and Fill State
- Per-Vertex Color State
- Shading State
- Texture State

Coordinates

System:
- Left-handed Cartesian coordinates
Converting from Right-Handed:
- Re-order vertices (e.g., a right-handed triangle with vertices \(v_0\), \(v_1\), \(v_2\) becomes a left-handed triangle with vertices \(v_0\), \(v_2\), \(v_1\))
- Multiply \(z\) values by -1

Vertices

Vertex Elements:
- Position
- Normal
- Color (D3DCOLOR_ARGB)
Process:
- Specify a custom struct for a vertex
- Specify a corresponding custom Flexible Vertex Format (FVF)
FVF Codes:
- Untransformed position: D3DFVF_XYZ
- Color Components: D3DFVF_DIFFUSE, D3DFVF_SPECULAR
- Normal: D3DFVF_NORMAL
- Point Size: D3DFVF_PSIZE

Vertices (cont.)

An Example

directx9examples/basics/cube/cube.cpp (Fragment: vertices)

Vertices (cont.)

Vertex Components:
- One or more vertex elements stored in a buffer (IDirect3DVertexBuffer9)
Process:
- Create the vertex buffer
  HRESULT CreateVertexBuffer(UINT size, DWORD usage, DWORD fvf, D3DPOOL pool, IDirect3DVertexBuffer9** vertexBuffer, NULL)
- Fill the vertex buffer with (a copy of) the vertices

Vertices (cont.)

Creating a Vertex Buffer

directx9examples/basics/cube/cube.cpp (Fragment: createBuffer)

Points, Lines and Polygons

Primitives:
- Point list, line list, line strip, triangle list, triangle strip, triangle fan
A Triangle Strip:
A Triangle Fan:

Points, Lines and Polygons

Nonindexed Rendering:
- HRESULT IDirect3DDevice9::DrawPrimitive(D3DPRIMITIVETYPE type, UINT startVertex, UINT primitiveCount)
Indexed Rendering:
- HRESULT IDirect3DDevice9::DrawIndexedPrimitive(D3DPRIMITIVETYPE type, INT offset, UINT minIndex, UINT numVertices, UINT startIndex, UINT count)

Points, Lines and Polygons (cont.)

Two 2D Triangles (Nonindexed):
- device->DrawPrimitive(D3DPT_TRIANGLELIST, 0, // startVertex 2); // primitiveCount
Two 2D Triangles (Indexed):
- device->DrawIndexPrimitive(D3DPT_TRIANGLELIST, 0, // offset 0, // minIndex 4, // numVertices (in total) 0, // startIndex 2); // primitiveCount

The Rendering Process

Starting the "Scene":
- IDirect3DDevice9::BeginScene()
Ending the "Scene":
- IDirect3DDevice9::EndScene()
Putting the "Scene" in the Off-Screen Buffer:
- IDirect3DDevice9::Present(NULL, NULL, NULL, NULL)

Rendering (cont.)

Binding Components/Buffers:
- Vertex components/buffers are bound to a device data stream using
  HRESULT IDirect3DDevice9::SetStreamSource(UNIT streamNumber, IDirect3DVertexBuffer9* streamData, UINT offset, UINT stride)
Identify the Fixed Function Vertex Shader:
- For basic usage, this involves passing the FVF code
  HRESULT IDirect3DDevice9::SetFVF(DWORD fvf)

Rendering (cont.)

An Example

directx9examples/basics/cube/cube.cpp (Fragment: render)

Viewing

World Matrix:
- Transformations to perform in model space
View Matrix:
- The "camera" for the scene
Projection Matrix
- How geometry is transformed from 3D view space to 2D viewport space

Viewing (cont.)

Declaring a Matrix:
- D3DXMATRIX
Transforms:
- D3DXMatrixRotation*(), D3DXMatrixReflect(), D3DXMatrixScaling(), D3DXMatrixTranslation(), etc...
Applying the Transform:
- HRESULT IDirect3DDevice9::SetTransform(D3DTRANSFORMSTATETYPE type, CONST D3DMATRIX* m)
- where type is D3DTS_VIEW, D3DTS_PROJECTION, or D3DTS_WORLD

Viewing (cont.)

Defining the View Transformation Matrix:
- Is usually done using a "convenience" method
Examples:
- D3DXMATRIX* D3DXMatrixLookAtLH(D3DXMATRIX* mOut, CONST D3DXVECTOR3* eye, CONST D3DXVECTOR3* at, CONST D3DXVECTOR3* up) where the LH indicates "left-handed"
- D3DXMATRIX* D3DXMatrixRotationYawPitchRoll(D3DXMATRIX* mOut,FLOAT yaw, FLOAT pitch, FLOAT roll) where the pitch is around \(x\), the yaw is around \(y\), and the roll is around \(z\)

The Projection Transform

Orthographic:
- D3DXMATRIX* D3DXMatrixOrthoLH(D3DXMATRIX* mOut, FLOAT w, FLOAT h, FLOAT znear, FLOAT zfar)
Perspective:
- D3DXMATRIX* D3DXMatrixPerspectiveFovLH(D3DXMATRIX* mOut, FLOAT fovy, FLOAT aspect, FLOAT znear, FLOAT zfar)

Viewing (cont.)

An Example

directx9examples/basics/cube/cube.cpp (Fragment: projection)

Transformations

Using a Mouse Callback

directx9examples/basics/cube/cube.cpp (Fragment: mousecallback)

There's Always More to Learn