How to set Environment Map reflection on one side only

Questions
1

I am using following code to import the .hdr file into the application

let hdrEquirect = new RGBELoader()
				.setDataType( THREE.UnsignedByteType)
				.setPath( 'textures/' )
				.load( 'in.hdr', function ( texture ) {

					init();
					animate();

				} );

And I am using following code for getting environment map from the hdr map

var pmremGenerator = new THREE.PMREMGenerator( renderer );
				hdrCubeRenderTarget = pmremGenerator.fromEquirectangular( hdrEquirect );
				hdrEquirect.dispose();
				pmremGenerator.dispose();

I haven’t use any lights into my scene. Still the sufficient amount of lighting also I got from this hdr itself.
I have imported some glb files into the scene.
I set the material as below for setting light and reflection as needed.

let transparent_glass_material = new THREE.MeshPhysicalMaterial( {
					color: 0x000000,
					metalness: 0,
					roughness: 0,
					alphaTest: 0.5,
					envMap:hdrCubeRenderTarget.texture,
					envMapIntensity: 1,
					depthWrite: false,
					transmission: 0.5, 
					opacity: 1,    
					reflectivity:1,
					clearcoat:1,                  
					transparent: true
				} );

Now one side of the object is being nice as per my need. But the other side also that reflection has takes place. I need to remove that reflection on one side. How to do that? Thanks in advance

2

Afaik, I don’t think that’s possible (or at least reasonable) to do with code, environment map is a sphere around your scene - it will affect the scene from any angle. Same goes for reflections.

Two “if it’s dumb but it works it’s not dumb” things you may do:

  1. If the way reflections appear on the model is static - ie. at all times there should be only reflection on one side and on the other not - just modify the model in Blender. Split the model into 2 submeshes in Edit Mode, then assign rough material to the non-reflective part and shiny material to the reflective part.
  2. You can try modifying the HDR texture in Photoshop - and just make a part you don’ want reflected black (it will then also not act as light on that part of the texture.) Sounds like something that may work, but never tried it so it’ll probably require some experimentation.