Displacement Fields don't cast shadows correctly?

[o_sidd42]

The block on the left is a normal cuboid, and you can see it casts a shadow beneath it, like it should.
The block in the middle is the same cuboid, but with a displacement field applied to its top surface only. It doesn't cast any shadow.
On the right is the same block, but with a displacement field applied to the bottom surface. For some reason though, it does cast a shadow!
Surely this behaviour is a bug? Has anyone noticed this happening before, and has anyone got a useful workaround? I'm getting irritating funny shadows in maps because of this.

[o_own3r]

The simple solution is to put brushes behind the surface of displacements to cast the shadow but this isn't ideal. One method Could be to create your displacements with all the sides nessisary to cast a shadow then fiddle them later so they are not visable? Displacements are designed to be "cheap" so its likely this isnt a bug but part of their design

[o_stino]

Originally Posted by Sidd42

The block on the left is a normal cuboid, and you can see it casts a shadow beneath it, like it should.
The block in the middle is the same cuboid, but with a displacement field applied to its top surface only. It doesn't cast any shadow.
On the right is the same block, but with a displacement field applied to the bottom surface. For some reason though, it does cast a shadow!
Surely this behaviour is a bug? Has anyone noticed this happening before, and has anyone got a useful workaround? I'm getting irritating funny shadows in maps because of this.

i don't have any troubles with displacement lighting becouse i always put block light brushes behind them, becouse if i put geometry trough the displacement, you can see the light coming trough just around the brush