unity urp内置的SAMPLER SamplerState

处理云阴影，打算直接在post阶段做个贴花了事

根据世界坐标的xz做为纹理采样的坐标,加上旋转缩放，形成运行的云阴影

采样器要用clamp方式

于是这样声明了一个

            SAMPLER(sampler_CloudTex)

            {

                Filter = MIN_MAG_MIP_LINEAR;

                AddressU = Clamp;//no work

                AddressV = Clamp;//no work

            };

发现不启作用

去官网看了一下，发现有内置的采样器定义

“Point”, “Linear” or “Trilinear” (required) set up texture filtering mode.

“Clamp”, “Repeat”, “Mirror” or “MirrorOnce” (required) set up texture wrap mode.Wrap modes can be specified per-axis (UVW), e.g. “ClampU_RepeatV”.

“Compare” (optional) set up sampler for depth comparison; use with HLSL SamplerComparisonState type and SampleCmp / SampleCmpLevelZero functions.

意思是根据名字组合，如

sampler_<过滤><UV处理>  形成一个变量名,用这个变量作为参数形成采样

例如：sampler_LinearClamp 这个表示采样过滤是linear,超过(0,1)用clamp方式采样

SAMPLER(sampler_LinearClamp);在shader里这样声明变量