Realistic Common Materials

Glass is the material beginners most often get wrong, usually by making it either a flat grey panel or an unnaturally clear void. Real glass does three things at once, and a believable glass material has to as well. It is transparent - you see through it, which in an engine means enabling transparency or transmission. It reflects, and this is the part people forget: real glass is a strong reflector, mirroring the sky and surroundings, especially at glancing angles. And it obeys Fresnel - the physical rule that every surface reflects far more light at a grazing angle than head-on. Look straight through a window and it is nearly clear; look along it at a shallow angle and it becomes a mirror of the sky. PBR builds Fresnel in automatically, which is a large part of why a properly-set glass reads as real. Keep glass roughness very low for clean windows (raise it slightly for frosted or etched glass), let it reflect the real environment - an HDRI sky pays off enormously here - and resist the urge to make it invisible; the reflections are what sell it.

Water is glass's close cousin and uses the same ideas with two additions. It has low roughness so it reflects sharply, it obeys the same Fresnel rule (which is why a lake mirrors the far shore at a distance but is clearer at your feet), and it usually carries a gentle refraction so submerged things bend, plus a moving normal map to give the surface its ripples and waves. Still water is nearly a mirror; disturbed water spreads those reflections into shimmer via its normal map. Both glass and water lean hardest of all materials on good reflections, so they are where a real, richly-graded HDRI sky and surroundings do the most work.

Metal is the one material where you definitely set metalness to 1, and that single flag changes everything about how it behaves: a metal has no plain diffuse colour, and instead its base colour tints its reflections. This is why gold reflects gold, copper reflects warm brown, and steel or aluminium reflects a near-neutral silver. Getting a metal to read starts with that: metalness at 1, and a base colour that is the metal's actual reflective tint rather than a painted-on surface colour.

With metalness settled, roughness does all the storytelling, and the range is wide. A near-zero roughness gives you a polished, mirror-like chrome or a still, gleaming brass. A mid roughness gives the soft, directional sheen of brushed steel or satin nickel - and brushed metals often use an anisotropic setting or a directional normal map so the highlight stretches along the brushing rather than forming a round spot, which is the tell of real brushed metal. A high roughness gives matte, blasted or powder-coated metal that barely reflects at all. So the same base colour and metalness can be a mirror-polished handrail or a matte-black steel frame purely through roughness. The most common beginner error with metal is making everything mirror-polished, which looks toy-like; most architectural metal is satin or brushed, not chrome. Add subtle wear, fingerprints or edge patina to lift it out of the too-clean trap, and metal quickly becomes one of the more satisfying materials to get right.

Wood is a non-metal (metalness 0) whose believability lives in three places. First, the grain - a good base colour and normal map carrying real timber grain, at correct plank scale, does most of the work; grain running the wrong direction or at the wrong size is an instant tell. Second, gloss variation: real wood is rarely uniformly shiny, because finish wears unevenly and the grain itself reflects differently along and across the fibre, so a roughness map that varies subtly across the surface reads far more real than a single flat roughness value. Third, scale and repetition - floorboards at true width, with the plank pattern broken up so the same knot does not appear on a grid. Get grain, subtle gloss variation and honest scale together and wood is convincing; miss any one and it reads as laminate.

Concrete is the workhorse of contemporary architecture and a material that rewards restraint. It is matte, so its roughness is high - concrete barely reflects, and making it too shiny is the classic way to ruin it. Its surface has fine relief - the pitting, board-marks and pores of real cast concrete - carried by a normal map, which under raking light is a huge part of what makes concrete read as a real poured surface rather than flat grey paint. And crucially, real concrete is mottled: never one even colour but a subtle map of lighter and darker patches, water staining, and tonal drift across the pour. A believable concrete is high roughness, a good relief normal, and that non-uniform, mottled colour - the opposite of the flat, clean grey a beginner reaches for. Both wood and concrete, in other words, are defeated by uniformity: the realism is in the variation.

Fabric rounds out the six, and it behaves unlike the hard materials because of how cloth scatters light. Its defining property is very high roughness - textiles are among the most diffuse, least reflective surfaces around, scattering light softly in every direction, which is why a sofa or a curtain looks soft rather than shiny. Start almost any fabric near the top of the roughness range. On top of that base, two touches make cloth read as cloth. A weave normal map gives the surface its fine texture - the visible warp and weft of linen, the nap of velvet, the twill of upholstery - which catches raking light exactly as a real weave does and is a big part of what separates real fabric from flat coloured plastic. And many fabrics carry a subtle sheen - the soft edge-glow you see on velvet, satin or silk, where light catches the tiny fibres at grazing angles - which modern PBR handles with a dedicated sheen or velvet setting.

Some fabrics are also translucent, letting light pass partly through - sheer curtains, lampshades, thin linen - which a translucency or subsurface setting captures, glowing softly when backlit by a window. This backlit glow is often the single most beautiful thing in an interior render, turning a plain curtain into a soft light source, so it is worth setting up deliberately rather than leaving curtains opaque. As with wood and concrete, variation and scale matter: a weave sized correctly (not stretched into giant threads) and broken up so it does not tile obviously, plus gentle colour variation and the natural folds and creases of real cloth, complete the illusion - and much of that softness actually comes from the geometry draping realistically, not the material alone, so a well-modelled cushion or throw does half the work. Put the six together - glass and water leaning on reflection and Fresnel, metal on metalness and roughness, wood and concrete on relief and mottling, fabric on high roughness and weave - and you can build almost any architectural scene convincingly. Every one, in the end, is the same small vocabulary of roughness, reflection and scale, applied with an eye for the variation that reality always carries.