How to normalize the direction to check if the player is able to move?

Question

I have a room with 4 walls along the x and z axis respectively. My player, who is in first person (therefore the camera), should have collision detection with these walls. I'm relatively new to this so please bare with me. I believe the way to do this is to calculate the direction and distance to the wall from the camera and then normalize the directions. However, I can only get this far before I don't know what to do. I think you should work out the angle and direction your facing?

Here _dx and _dz is the small buffer in front of the camera.

float CalcDirection(float Cam_x, float Cam_z, float Wall_x, float Wall_z)
{
    //Calculate direction and distance to obstacle.
    float ob_dirx = Cam_x + _dx - Wall_x;
    float ob_dirz = Cam_z + _dz - Wall_z;
    float ob_dist = sqrt(ob_dirx*ob_dirx + ob_dirz*ob_dirz);

    //Normalise directions
    float ob_norm = sqrt(ob_dirx*ob_dirx + ob_dirz*ob_dirz);
    ob_dirx = (ob_dirx)/ob_norm;
    ob_dirz = (ob_dirz)/ob_norm;

Can anyone explain in layman's terms how I work out the angle?

Answer 1

This is actually a well documented problem. What you want isn't the distance from the camera to a specific point on the wall (Wall_x,Wall_z). Rather, you can find the point on a wall which is closest to the camera, at any time. This article should tell you all about the math involved, even though it's for ActionScript.

Once you know the point which is closest, finding the distance and direction is trivial. Actually, you can look at the whole thing as collision detection between a circle (around the camera) and a line (a wall) in 2D (seen top-down, ignoring the y dimension).