Special Effects

Microsoft DirectX 8.1 (Visual Basic)

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 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.
lFVFTex = (D3FVF_TEX1 Or 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  0  0 (du and dv change each frame)
'      0   0  0  0
dx.IdentityMatrix(M)
M.rc31 = du
M.ec32 = 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)