Sandbox.Ray

// From position and direction
Ray ray = new Ray(origin, direction);

// From camera
Ray ray = Scene.Camera.ScreenPixelToRay(mousePos);

// Intersect with plane
float? dist = ray.IntersectPlane(plane, out Vector3 hitPoint);

// Intersect with box
float? dist = ray.IntersectBox(box, out Vector3 hitPoint);

// Intersect with sphere
float? dist = ray.IntersectSphere(center, radius, out Vector3 hitPoint);

// Intersect with triangle
float? dist = ray.IntersectTriangle(v0, v1, v2, out Vector3 hitPoint);

// Get point at distance along ray
Vector3 point = ray.Project(distance);

// Closest point to another point
Vector3 closest = ray.ClosestPoint(targetPos);

// Physics raycast
var tr = Scene.Trace.Ray(ray, 10000).Run();

if (tr.Hit)
{
    Vector3 hitPos = tr.EndPosition;
}

// Weapon firing
Ray aimRay = new Ray(gunPos, gunRotation.Forward);
var tr = Scene.Trace.Ray(aimRay, 10000).Run();

// Mouse picking
Ray mouseRay = Scene.Camera.ScreenPixelToRay(Input.MousePosition);