Hi,

Follow the instructions written under this post: https://my.aximmetry.com/post/2365-how-to-get-hi-res-virtual-shadows-in-the 

However, keep in mind that billboards are merely 2D flat surfaces. Consequently, the shadows cast on them may not appear fully realistic.

Warmest regards,

Thank you for your tutorial. I solved this problem in version 5.1 according to the tutorial, but I did not find the button in the tutorial in 5.4. Can I ask if it can only be implemented in version 5.1?

Hi,

You need to set the same setting, but since version 5.4, the Billboard is composed of two materials: "Billboard_After_DOF" and "Billboard_After_Motion_Blur".
If there are reflections in your scene, you likely need to set the Lighting Mode to Surface Forward Shading in both materials. This ensures that shadows will appear on the Billboard in the reflections as well.
If reflections are not a concern, you only need to adjust this setting for the "Billboard_After_Motion_Blur" material.

Warmest regards,