Texture Coordinate Register

This vertex shader output register contains per-vertex texture coordinates.

A register consists of properties that determine how each register behaves.

PropertyDescription
NameoT0 - oT7
CountEight vectors
I/O permissionsWrite-only

 

The output texture coordinates registers are an array of output data registers. The register data is iterated and used as texture coordinates by the texture sampling stages to supply data to the pixel shader.

When writing to a texture coordinate register, it is recommended that you pass only as many floating point values as the dimension of the corresponding texture map. Control the values that are passed with a modifier. For example, use .xy for a 2D texture map.

The fixed function vertex pipeline flags, D3DTEXTURETRANSFORMFLAGS (D3DTTFF_COUNT1, D3DTTFF_COUNT2, D3DTTFF_COUNT3, D3DTTFF_COUNT4), should be set to zero if you are using a programmable vertex shader.

Object vertex data supplies input texture coordinates. Objects that do not use tiled textures commonly have texture coordinates in the range [0,1]. Objects that use tiled textures, such as terrain, typically have texture coordinates that range from [-n,+n] where n can be any floating point number.

Texture coordinate interpolation is performed on vertex data for rasterization. During rasterization, texture coordinates are interpolated between object vertices, modified by texture wrapping, and scaled by the texture size (also taking into account texture addressing modes) to produce an integer index. The index is then used to perform a texture lookup. Use the MaxTextureRepeat value in D3DCAPS9 to determine how many times a texture can be tiled.

Example

Declare the texture coordinate register.



dcl_texcoord v7


Copy the per-vertex texture coordinates to the output register.



mov oT0, v7


Vertex shader versions1_12_02_sw2_x3_03_sw
Texture Coordinate Registerxxxxxx

 

Related topics

Vertex Shader Registers

 

 

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