Combining materials with and without an opacity map causes the material without opacity map to become fully transparent.
Demo link:
https://cdn.pbr.one/0.3.0/pbr-material.html#material_name=Bricks;Metal-Walkway,color_url=https://pbr.one/media/bricks_col.jpg;https://pbr.one/media/walkway_col.jpg,normal_url=https://pbr.one/media/bricks_nrm.jpg;https://pbr.one/media/walkway_nrm.jpg,roughness_url=https://pbr.one/media/bricks_rgh.jpg;https://pbr.one/media/walkway_rgh.jpg,displacement_url=https://pbr.one/media/bricks_dsp.jpg;https://pbr.one/media/walkway_dsp.jpg,metalness_url=;https://pbr.one/media/walkway_met.jpg,opacity_url=;https://pbr.one/media/walkway_opa.jpg,displacement_scale=0.01,tiling_scale=2,geometry_type=plane,clayrender_enable=0,geometry_subdivisions=400
Combining materials with and without an opacity map causes the material without opacity map to become fully transparent. Demo link:
https://cdn.pbr.one/0.3.0/pbr-material.html#material_name=Bricks;Metal-Walkway,color_url=https://pbr.one/media/bricks_col.jpg;https://pbr.one/media/walkway_col.jpg,normal_url=https://pbr.one/media/bricks_nrm.jpg;https://pbr.one/media/walkway_nrm.jpg,roughness_url=https://pbr.one/media/bricks_rgh.jpg;https://pbr.one/media/walkway_rgh.jpg,displacement_url=https://pbr.one/media/bricks_dsp.jpg;https://pbr.one/media/walkway_dsp.jpg,metalness_url=;https://pbr.one/media/walkway_met.jpg,opacity_url=;https://pbr.one/media/walkway_opa.jpg,displacement_scale=0.01,tiling_scale=2,geometry_type=plane,clayrender_enable=0,geometry_subdivisions=400