base
The base color texture. The first three components (RGB) MUST be encoded with the sRGB transfer function. They specify the base color of the material. If the fourth component (A) is present, it represents the linear alpha coverage of the material. Otherwise, the alpha coverage is equal to 1.0. The material.alphaMode property specifies how alpha is interpreted. The stored texels MUST NOT be premultiplied. When undefined, the texture MUST be sampled as having 1.0 in all components.