Tiny Online Tools
What you are actually editing
A glTF material is a small set of numbers, not an image. baseColorFactor, metallicFactor, roughnessFactor, emissiveFactor, alphaMode, alphaCutoff and doubleSided describe how light behaves on the surface; textures, when present, modulate those numbers per pixel. This editor changes the numbers and leaves everything else in the file exactly as it was.
Metallic and roughness are not "shininess"
Metallic is close to a binary property in the real world. A surface is either a conductor — bare metal, where reflections take on the metal's own colour and there is no diffuse component at all — or it is not. Values between 0 and 1 exist mostly for blended edges, worn paint and dirt layers. If a plastic part looks wrong, the fix is almost never "a bit of metallic"; it is roughness.
Roughness controls how tightly reflections gather. At 0 you get a mirror; at 1 you get a diffuse, chalky surface. Most real materials sit between 0.3 and 0.7. The single most common mistake in exported models is roughness left at 0, which makes everything look like wet plastic under a studio light.
Alpha mode matters more than it looks
OPAQUE ignores the alpha channel entirely and is the fastest path. MASK cuts pixels away when alpha falls under the cutoff — the right choice for leaves, chain link, decals and hair cards, because it needs no sorting. BLEND genuinely blends, which means the renderer must depth-sort every transparent surface and will still get it wrong from some angles.
Many exporters mark every material BLEND by default. Switching the opaque ones back to OPAQUE often fixes flickering, wrongly-ordered geometry and a surprising amount of GPU cost.
The linear versus sRGB trap
Colour pickers speak sRGB. glTF stores baseColorFactor and emissiveFactor as linear values. They are not the same number: mid grey is 0.502 in sRGB and 0.216 in linear. Write the sRGB number straight into the file and every colour comes out too light. This tool converts in both directions for you, and shows the linear factor next to the swatch so you can check it. Alpha is deliberately left alone — it is coverage, not light, and has no gamma curve.
Private by design
Parsing, editing, previewing and export all run locally. Your model never leaves the browser.