Special Effects

Microsoft DirectX 8.1 (C++)

Special Effects

The following list contains examples of special effects accomplished with texture coordinate processing.

Animating textures (by translation or rotation) on a model

Define two-dimensional (2-D) texture coordinates in your vertex format.

// Use a single texture, with 2-D texture coordinates. This
// bit-pattern should be expanded to include position, normal, 
// and color information as needed.
DWORD dwFVFTex = D3FVF_TEX1 | D3DFVF_TEXCOORDSIZE2(0);

Configure the rasterizer to use 2-D texture coordinates.

SetTextureStageState(0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_COUNT2);

Define and set an appropriate texture coordinate transformation matrix.

// M is a D3DMATRIX being set to translate texture
// coordinates in the U and V directions.
//      1   0  0  0
//      0   1  0  0
//      du dv  1  0 (du and dv change each frame)
//      0   0  0  1

D3DMATRIX M = D3DXMatrixIdentity(); // declared in d3dutil.h
M._31 = du; 
M._32 = dv;

Creating texture coordinates as a linear function of a model's camera-space position

Use the D3DTSS_TCI_CAMERASPACEPOSITION flag to instruct the system to pass the vertex position, in camera space, as input to a texture transformation.

// The input vertices have no texture coordinates, saving 
// bandwidth. Three texture coordinates are generated by 
// using vertex position in camera space (x, y, z).
SetTextureStageState(0, D3DTSS_TEXCOORDINDEX, D3DTSS_TCI_CAMERASPACEPOSITION);

Instruct the rasterizer to expect 2-D texture coordinates.

// Two output coordinates are used.
SetTextureStageState(0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_COUNT2);

Define and set a matrix that applies a linear function.

// Generate texture coordinates as linear functions 
// so that:
//      u = Ux*x + Uy*y + Uz*z + Uw 
//      v = Vx*x + Vy*y + Vz*z + Vw
// The matrix M for this case is:
//      Ux  Vx  0  0 
//      Uy  Vy  0  0 
//      Uz  Vz  0  0 
//      Uw  Vw  0  0 

SetTransform(D3DTS_TEXTURE0, &M);

Performing environment mapping with a cubic environment map

Use the D3DTSS_TCI_CAMERASPACEREFLECTIONVECTOR flag to instruct the system to automatically generate texture coordinates as reflection vectors for cubic mapping.
```
SetTextureStageState(0, D3DTSS_TEXCOORDINDEX, D3DTSS_TCI_CAMERASPACEREFLECTIONVECTOR);
```
Instruct the rasterizer to expect texture coordinates with three elements.
```
SetTextureStageState(0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_COUNT3);
```

Performing projective texturing

Use the D3DTSS_TCI_CAMERASPACEPOSITION flag to instruct the system to pass the vertex position as input to a texture transformation matrix.
```
SetTextureStageState(0, D3DTSS_TEXCOORDINDEX, D3DTSS_TCI_CAMERASPACEPOSITION);
```
Create and apply the texture projection matrix. This is beyond the scope of this documentation, and is the topic of several industry articles.

Instruct the rasterizer to expect three-element projected texture coordinates.

// Two output coordinates are used.
SetTextureStageState(0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTF_PROJECTED | D3DTTFF_COUNT3);