# What is the "TangentsW" attribute inside the FBX file format for?

sometimes it is -1, sometimes is +1. Do I need it for the rendering of the normal maps?

Looks like the tangent handedness that's needed for proper normal mapping. It can be used for calculating the bitangent for TBN matrix. Example in GLSL: vec3 bitangent = normalize( normalMatrix * (cross( aNormal, aTangent.xyz ) * aTangent.w) );