Implemented @bhouston's #7420.

src/renderers/shaders/ShaderChunk/lights_standard_fragment.glsl

@@ -1,4 +1,4 @@
 PhysicalMaterial material;
 material.diffuseColor = diffuseColor.rgb * ( 1.0 - metalnessFactor );
-material.specularRoughness = roughnessFactor * 0.5 + 0.5; // disney's remapping of [ 0, 1 ] roughness to [ 0.5, 1 ]
+material.specularRoughness = clamp( roughnessFactor, 0.04, 1.0 ); // disney's remapping of [ 0, 1 ] roughness to [ 0.04, 1 ]
 material.specularColor = mix( vec3( 0.04 ), diffuseColor.rgb, metalnessFactor );