/// <summary>
/// This method can be used to check if the specified 2D ray intersects the circle.
/// </summary>
/// <param name="ray">
/// The ray involved in the intersection test.
/// </param>
/// <param name="t">
/// If the ray intersects the circle, this will hold the intersection offset between
/// the ray and the circle. It will always have a value in the interval [0, 1]. If no
/// intersection happens, it will be set to 0.
/// </param>
/// <returns>
/// True if an intersection happens and false otherwise.
/// </returns>
public bool Raycast(Ray2D ray, out float t)
{
t = 0.0f;
// Calculate the equation coefficients
Vector2 fromCenterToRayOrigin = ray.Origin - _center;
float a = Vector3.Dot(ray.Direction, ray.Direction);
float b = 2.0f * Vector3.Dot(fromCenterToRayOrigin, ray.Direction);
float c = Vector3.Dot(fromCenterToRayOrigin, fromCenterToRayOrigin) - _radius * _radius;
// If the equation can be solved, it means that ray intersects the circle
float t1, t2;
if (Equation.SolveQuadratic(a, b, c, out t1, out t2))
{
// Make sure that the ray does not intersect the circle from behind or that the intersection
// offset doesn't exceed the length of the ray direction.
if (t1 < 0.0f || t1 > 1.0f)
{
return(false);
}
// Store the intersection offset and return true
t = t1;
return(true);
}
else
{
return(false); // The equation could not be solved, so no intersection occurs
}
}
public bool Raycast(Ray ray, out float t)
{
t = 0.0f;
// Calculate the coefficients of the quadratic equation
Vector3 sphereCenterToRayOrigin = ray.origin - _center;
float a = Vector3.SqrMagnitude(ray.direction);
float b = 2.0f * Vector3.Dot(ray.direction, sphereCenterToRayOrigin);
float c = Vector3.SqrMagnitude(sphereCenterToRayOrigin) - _radius * _radius;
// If we have a solution to the equation, the ray most likely intersects the sphere.
float t1, t2;
if (Equation.SolveQuadratic(a, b, c, out t1, out t2))
{
// Make sure the ray doesn't intersect the sphere only from behind
if (t1 < 0.0f && t2 < 0.0f)
{
return(false);
}
// Make sure we are using the smallest positive t value
if (t1 < 0.0f)
{
float temp = t1;
t1 = t2;
t2 = temp;
}
t = t1;
return(true);
}
// If we reach this point it means the ray does not intersect the sphere in any way
return(false);
}
