Use the Unreal Engine to output the shadow of a certain object,(使用虚幻引擎输出某个物体的感觉的阴影)

How can the Unreal Engine obtain the individual shadow of a certain object? The shadow produced by this bridge is also present. How can it be removed? I used the method shown in the following picture to create the shadow layer, but the self-shadow of the bridge could not be removed.