I want to use shader to adjust 3dtiles`s Brightness,Contrast,Hue and Saturationm how do i add my shader to without modify source code
You can create a custom post process in CesiumJS: https://sandcastle.cesium.com/index.html?src=Custom%20Post%20Process.html
Otherwise custom shaders on 3D Tiles aren’t currently supported but we have a GitHub issue for this here: https://github.com/CesiumGS/cesium/issues/7652.