I'm using the PerspectiveCamera class in C#/WPF to implement an FPS style camera.
For that, I would need to offset the camera's horizontal and vertical angles every time the mouse is moved. The problem is that PerspectiveCamera doesn't store those angles and only provides a lookat vector.
So, is there a way to calculate those angles from the lookat vector ?
If there is no roll in your FPS camera (typically, there is not in an FPS) then all you need to do to get a yaw angle (-π..π ) from the vector is the atan2() function.
As suggested by DMGregory, the arcsin of the z component of the forward vector gives the tilt angle.
#include <math.h>
...
// calculate yaw
const float yaw_angle = atan2f( cam_fwd.y, cam_fwd.x );
// calculate pitch
const float pitch_angle = asinf( cam_fwd.z );
This assumes you know where the camera is looking (cam_fwd.)
lookat too — in some contexts this is used to mean a worldspace point the camera should look towards, but in your example above it looks like you mean it to be the camera's forward direction vector or the offset from the camera position to a point in the center of the camera's view some distance away.
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