Estimates the arctangent of Y/X.
XMVECTOR XMVectorATan2Est(
XMVECTOR Y,
XMVECTOR X
)
Y
Type: XMVECTOR
First vector.
X
Type: XMVECTOR
Second vector.
Type: XMVECTOR
Returns a vector. Each component is an estimate of the arctangent of the corresponding Y component divided by the corresponding X component. Each component is in the range (-PI/2, PI/2).
XMVectorATan2Est returns the following values for the specified special input values.
| Input Value | Return Value |
|---|---|
| Y == 0 and X < 0 | Pi with the same sign as Y |
| Y == 0 and X > 0 | 0 with the same sign as Y |
| Y != 0 and X == 0 | Pi / 2 with the same sign as Y |
| X == -Infinity and Y is finite | Pi with the same sign as Y |
| X == +Infinity and Y is finite | 0 with the same sign as Y |
| Y == Infinity and X is finite | Pi / 2 with the same sign as Y |
| Y == Infinity and X == -Infinity | 3Pi / 4 with the same sign as Y |
| Y == Infinity and X == +Infinity | Pi / 4 with the same sign as Y |
Est functions offer increased performance at the expense of reduced accuracy. Est functions are appropriate for non-critical calculations where accuracy can be sacrificed for speed. The exact amount of lost accuracy and speed increase are platform dependent.
This function uses a 9-degree minimax approximation.
Header: Declared in directxmath.h.