// MouseToWorldRay
//
// This takes the view matricies, and a window-local mouse coordinate, and returns a ray in world space.
public static SSRay MouseToWorldRay(
Matrix4 projection,
Matrix4 view,
System.Drawing.Size viewport,
Vector2 mouse)
{
// these mouse.Z values are NOT scientific.
// Near plane needs to be < -1.5f or we have trouble selecting objects right in front of the camera. (why?)
Vector3 pos1 = UnProject(ref projection, view, viewport, new Vector3(mouse.X, mouse.Y, -1.5f)); // near
Vector3 pos2 = UnProject(ref projection, view, viewport, new Vector3(mouse.X, mouse.Y, 1.0f)); // far
return(SSRay.FromTwoPoints(pos1, pos2));
}
/// <summary>
/// Distance from a ray to a point at the closest spot. The ray is assumed to be infinite length.
/// </summary>
/// <param name="ray"></param>
/// <param name="point"></param>
/// <returns></returns>
public static float DistanceToLine(SSRay ray, Vector3 point, out float distanceAlongRay)
{
// http://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line
Vector3 a = ray.pos;
Vector3 n = ray.dir;
Vector3 p = point;
var t = Vector3.Dot((a - p), n);
distanceAlongRay = -t;
return(((a - p) - t * n).Length);
}
// Ray to AABB (AxisAlignedBoundingBox)
// http://gamedev.stackexchange.com/questions/18436/most-efficient-aabb-vs-ray-collision-algorithms
public static bool intersectRayAABox2(SSRay ray, SSAABB box, ref float tnear, ref float tfar)
{
Vector3d T_1 = new Vector3d();
Vector3d T_2 = new Vector3d(); // vectors to hold the T-values for every direction
double t_near = double.MinValue; // maximums defined in float.h
double t_far = double.MaxValue;
for (int i = 0; i < 3; i++)
{ //we test slabs in every direction
if (ray.dir[i] == 0)
{ // ray parallel to planes in this direction
if ((ray.pos[i] < box.Min[i]) || (ray.pos[i] > box.Max[i]))
{
return(false); // parallel AND outside box : no intersection possible
}
}
else
{ // ray not parallel to planes in this direction
T_1[i] = (box.Min[i] - ray.pos[i]) / ray.dir[i];
T_2[i] = (box.Max[i] - ray.pos[i]) / ray.dir[i];
if (T_1[i] > T_2[i])
{ // we want T_1 to hold values for intersection with near plane
var swp = T_2; // swap
T_1 = swp; T_2 = T_1;
}
if (T_1[i] > t_near)
{
t_near = T_1[i];
}
if (T_2[i] < t_far)
{
t_far = T_2[i];
}
if ((t_near > t_far) || (t_far < 0))
{
return(false);
}
}
}
tnear = (float)t_near; tfar = (float)t_far; // put return values in place
return(true); // if we made it here, there was an intersection - YAY
}
} // fn
public static bool intersectRayAABox1(SSRay ray, SSAABB box, ref float tnear, ref float tfar)
{
// r.dir is unit direction vector of ray
Vector3 dirfrac = new Vector3();
float t;
dirfrac.X = 1.0f / ray.dir.X;
dirfrac.Y = 1.0f / ray.dir.Y;
dirfrac.Z = 1.0f / ray.dir.Z;
// lb is the corner of AABB with minimal coordinates - left bottom, rt is maximal corner
// r.org is origin of ray
float t1 = (box.Min.X - ray.pos.X) * dirfrac.X;
float t2 = (box.Max.X - ray.pos.X) * dirfrac.X;
float t3 = (box.Min.Y - ray.pos.Y) * dirfrac.Y;
float t4 = (box.Max.Y - ray.pos.Y) * dirfrac.Y;
float t5 = (box.Min.Z - ray.pos.Z) * dirfrac.Z;
float t6 = (box.Max.Z - ray.pos.Z) * dirfrac.Z;
float tmin = Math.Max(Math.Max(Math.Min(t1, t2), Math.Min(t3, t4)), Math.Min(t5, t6));
float tmax = Math.Min(Math.Min(Math.Max(t1, t2), Math.Max(t3, t4)), Math.Max(t5, t6));
// if tmax < 0, ray (line) is intersecting AABB, but whole AABB is behing us
if (tmax < 0)
{
t = tmax;
return(false);
}
// if tmin > tmax, ray doesn't intersect AABB
if (tmin > tmax)
{
t = tmax;
return(false);
}
t = tmin;
return(true);
}
public static float DistanceToLine_2(SSRay ray, Vector3 point)
{
return(Vector3.Cross(ray.dir, point - ray.pos).Length);
}
