const float M_PI = 3.1415926535897932384626433832795;
const float M_2PI = 2.0 * M_PI;
const float M_INV_PI = 0.31830988618379067153776752674503;
const float M_INV_LOG2 = 1.4426950408889634073599246810019;
Default background colors when there is no data in channel (alpha is 0)
const vec4 CHANNELS_BACKGROUND = vec4(
0.5, // BaseColor
0.3, // Roughness
0.0, // Metallic
0.0 // Unused
);