Hello Folks 
I have created this sandbox in which i want to SCALE the reflection created by cubecamera.
Cubecamera is inside right box which is made by combination of plane geometry and reflection is on left box.( The reflection is quite big as seen on left box).
What you want to achieve does not work. The reason for this is explained in three.js - Make environment map scale when moving from the object - Stack Overflow
Relevant section:
Environment mapping in three.js is based on the assumption that the object being reflected is “infinitely” far away from the reflective surface.
Since you want to show the reflection of a mesh on another mesh near by, this technique won’t produce the expected result.
Your reflection depends on the image that your webglcuberendertarget camera can see.
Any possible solutions for this?