Transform texture coordinates when using shader

Question

Assuming I define four vertices of a quad with texture coordinates that cover a whole texture or region of a texture, I can animate these coordinates by setting a transform using

SetTransform( D3DTS_TEXTURE0, &texTrans )

...scaling, translating etc.

If I render using a shader, and still want to animate the coordinates, presumably I can pass in the same transformation matrix and multiply the coordinates in the vertex shader?

Instead of in the vertex shader

Output.TextureUV = vTexCoord0; 

do

Output.TextureUV = mul( vTexCoord0, texTrans );

Is this a/the correct way to render an animated sprite with shader?

Answer 1

I just stumbled back on this question, so I figure I should supply an answer. :)

The shader code I wrote in the question is almost right. I forgot that to convert a point with these transformations, the point needs to be in homogeneous coordinates.

See: https://stackoverflow.com/questions/5066532/how-to-multiple-a-2d-point-with-a-4d-matrix

So the correct vertex shader code would be:

Output.TextureUV = mul( float4( vTexCoord0, 0.0f, 1.0f ), texTrans );