when using uv0 to sample texture is correct.
but when using uv1, there is enlargement in preview.
to make sure this is not default cube’s uvs problem, I made a simple triangle. But still incorrect.
Figured it out. It is default cube’s uv cause this. Just need to use .Clear() before set exist mesh’s propertied, or the uv2 or after uvs is different from uv0.
(This problem made me to learn shaderlab and hlsl in the last two weeks, what a tragedy…)