About W component of tangent

/** Sets whether to store tangent space parity in the W of a 4-component tangent or not.
@ Remarks
The default element format to use is vet_float3 which is enough to accurately
Deal with tangents that do not involve any texture coordinate locking ing.
If you wish to allow UV indexing ing in your model, you must enable 4-component
Tangents using this method, and the 'W' co-ordinate will be populated
With the parity of the triangle (+ 1 or-1), which will allow you to generate
The bitangent properly.
@ Param enable true to enable 4-component tangents (default false). If you enable
This, you will probably also want to enable mirror splitting (see setsplitmirrored ),
And your shader must understand how to deal with the parity.
*/
Void setstoreparityinw (bool enabled) {mstoreparityinw = enabled ;}

 

4-The W of component is the tangent direction used to store and process image UV, which must be matched in the shader.