To set up reflections in vim3D, simply use the reflection command to set the reflective value for each color component:

reflection 0.7 0.7 0.7

The scene description for this image is below:

add cam
name renderCam
position 17.845837 26.321945 -38.120468
camera lookat 15.155572 22.831070 -31.443937
up 0.015374 0.996323 0.084284


add grid 4
poly centroid
poly scale 60
ambient 0.2 0.2 0.2 1
reflection 0.1 0.1 0.1

add grid 4
poly centroid
poly scale 60
poly rotate 90 0 0 1
poly translate 80 0 0
ambient 0.4 0.1 0.1 1
reflection 0.0 0.0 0.0

add grid 4
poly centroid
poly scale 60
poly rotate 90 0 0 1
poly translate -80 0 0
ambient 0.1 0.4 0.1 1
reflection 0.0 0.0 0.0

add grid 4
poly centroid
poly scale 60
poly rotate 90 1 0 0
poly translate 0 0 -80
ambient 0.1 0.1 0.4 1
reflection 0.0 0.0 0.0

add sphere
m 20 18 0
diffuse .2 .6 0.6 1
ambient 0 0.3 0.3 1
reflection 0.6 0.6 0.6

add sphere
m 0 18 0
diffuse .6 .6 .2 1
ambient 0.2 0.2 0 1
reflection 0.6 0.6 0.6

add light 
m -11 31 -17

add light 
diffuse .4 0.4 0.4 1
m 11 31 17