will want to subdivide box object. without LOD expect to not function well close to faces of the box etc.
correct depth mapping may be an issue (unless maybe if restrict FOV to <180), since appears that in webgl, can't explicitly set depth in frag shader.
this kind of thing maybe unnecessary on a decent PC (cubemap works fine), but may notice on mobile, and, in a larger project where want to do reflections in spheres, something like this may be more realistic (otherwise rendering a lot of views!)
basically implement http://www.gamasutra.com/blogs/BrianKehrer/20160125/264161/VR_Distortion_Correction_using_Vertex_Displacement.php
will want to subdivide box object. without LOD expect to not function well close to faces of the box etc. correct depth mapping may be an issue (unless maybe if restrict FOV to <180), since appears that in webgl, can't explicitly set depth in frag shader. this kind of thing maybe unnecessary on a decent PC (cubemap works fine), but may notice on mobile, and, in a larger project where want to do reflections in spheres, something like this may be more realistic (otherwise rendering a lot of views!)