Any surface (flats or walls) can be rendered with shiny surface properties. This allows for some very interesting tricks to be created such as specular “reflections”. You can use a mask with the shiny surfaces to mask out areas of shininess but a mask can be used to also increase the effect of shininess on areas of a texture. Reflection definitions support the use of any of the new blending mode flags such as add and subtract.

Reflection
{
   Texture = "";
       # The wall texture this reflection will be associated with. A 
       # reflection can only be associated with either a texture or a 
       # flat, not both.
   Flat = "";
       # The flat this reflection will be associated with.
   Flags = flaga | flagb | flagc etc...
       # NEW in 1.9.0-beta6
       # noiwad: Don't use this reflection if the resource is loaded from an IWAD.
       # pwad: This reflection can be used with PWAD resources (for example custom textures).
       # ext: This reflection can be used with external resources.
   Blending mode = add;
       # One of the bm_* flags defined in Flags.ded. By default 
       # reflections use additive blending.
   Shininess = 1.0;
       # Strength of the shiny effect. 1.0 is the maximum value. This
       # is used as the alpha component when doing blending.
   Min color { 0.0 0.0 0.0 }
       # By default the shiny effect uses sector light as the basic color
       # of the effect. The Min color RGB values (0..1) can be used to
       # set a minimum light level for the effect so it'll show up even
       # in very dark sectors.
   Shiny map = "";
       # Name of the external resource that is used as the shiny map for
       # this reflection. By default the resource is searched in the
       # LightMaps resource directory. The shiny map is mapped onto 
       # reflecting surfaces using a mapping that resembles cylindrical
       # environment mapping. The dimensions of the map must be powers
       # of two, for example 128 x 64 or 32 x 128.
   Mask map = "";
       # Name of the external resource that is used to mask out the 
       # shininess of a surfaces. The mask map is mapped onto surfaces 
       # using the same texture coordinates that are used for mapping 
       # regular textures. The darker the texel in the mask, the fainter
       # the reflection becomes. The dimensions of the map must be powers
       # of two, for example 128 x 64 or 32 x 128.
   Mask width = 1.0;
       # A factor for the width of the mask. This can be used to make the
       # mask span beyond the mapping of the regular texture of the 
       # surface. For example, consider a surface with a texture that is
       # 64 texels wide. Regardless of the mask's horizontal resolution,
       # the mask is always mapped onto the regular texture so that their
       # edges overlap. If the mask width value is 1.0, the mask is as 
       # wide as the 64 texel original texture. If mask width is increased 
       # to 2.0, the mask is mapped so that it is as wide as a 128 texel 
       # texture.
   Mask height = 1.0;
       # A factor for the height of the mask.
}