Hi,
This function apply inverse transform without scaling the vector. For example, you have transform with scale 10 and rotation on 10 degrees around X-axis. In the result you will achieve vector rotated around X axis on -10 degrees rad.
Here is some example.
Transform transform(FRotator(90, 0, 0), FVector(0, 0, 0), FVector(10, 10, 10));
FVector r1 = transform.TransformVector(FVector(1, 0, 0)); // 0 0 10 scale in 10 and rotate on 90 degrees
FVector r2 = transform.InverseTransformVector(FVector(1, 0, 0)); // 0 0 -0.1 scale in 0.1 and rotate on -90 degrees
FVector r3 = transform.InverseTransformVectorNoScale(FVector(1, 0, 0)); // 0 0 -1 no scale and rotate on -90 degrees
Best regards,