Introduction to glTF and Physically Based Rendering for 3D Artists
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What glTF is, why it is called the JPEG of 3D, and what physically based rendering asks of an artist. The lecture walks through the metallic-roughness material maps one at a time: base color, metallic, roughness, normal, occlusion and emissive. It shows how roughness spreads a reflection, and closes with three practical habits for painting and packing textures that look right in any glTF viewer.
You have finished a model, and you want it to look right in a web browser, a game engine, and a client's viewer. That is the job G L T F was made for. It packs your mesh, your materials, and your textures into one tidy file. That is why people call it the JPEG of three D: compact, standard, and ready to display anywhere. Its materials follow an idea called physically based rendering, or P B R. Instead of painting how a surface looks under one light, you describe what the surface is made of. Then the renderer handles the light. Move the lamp, and the reflection moves with it, worked out for you. The same material behaves believably at noon, at dusk, or in a dark room.
G L T F describes that material with a small set of maps, called the metallic roughness workflow. Here they are, beside a lit surface we can adjust. Base color is the pure color of the surface, with no shadows or highlights painted in. Metallic says whether it is metal. Zero for paint, plastic, wood or skin, and one for bare metal. Most surfaces are simply one or the other. Roughness controls how blurry reflections are. At zero the surface is glossy, and the reflection is one sharp beam. Raise it, and the light scatters into a soft, matte spread. A normal map fakes small bumps and scratches without adding geometry. Occlusion darkens the crevices where light struggles to reach. And emissive marks the parts that glow on their own, like screens or lamps. A few habits keep these maps honest. First, keep base color clean. Lighting belongs to the renderer, so do not bake shadows into it. Second, think in clear choices. Metal is metal and paint is paint; save the in between values for dust, rust, and worn edges. Third, know the packing. G L T F reads roughness from the green channel and metallic from the blue channel of one image, and occlusion usually fills the red. So export them together. Paint what the surface is, let the light do the rest, and your model will look right wherever G L T F takes it.
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