public Option <RayHitpoint> TryHit(PositionableSphere positionableSphere, Ray ray, RayParameter bottomBoundary,
RayParameter topBoundary)
{
var(positionable, sphere) = positionableSphere;
var originToCenter = ray.Origin - positionable.Translation;
var a = Vector3.Dot(ray.Direction, ray.Direction);
var b = 2.0f * Vector3.Dot(originToCenter, ray.Direction);
var c = Vector3.Dot(originToCenter, originToCenter) -
sphere.Radius * sphere.Radius;
var discriminant = b * b - 4 * a * c;
if (discriminant < 0)
{
return(Option <RayHitpoint> .Empty);
}
var temp = new RayParameter((-b - (float)Math.Sqrt(discriminant)) / (2.0f * a));
if (temp < topBoundary.Value && temp > bottomBoundary.Value)
{
var hitPoint = ray.PointAt(temp);
var normal = GetNormalAtPoint(hitPoint, positionableSphere);
return(new Option <RayHitpoint>(new RayHitpoint(hitPoint, normal, temp)));
}
temp = new RayParameter((-b + (float)Math.Sqrt(discriminant)) / (2.0f * a));
if (temp < topBoundary.Value && temp > bottomBoundary.Value)
{
var hitPoint = ray.PointAt(temp);
var normal = GetNormalAtPoint(hitPoint, positionableSphere);
return(new Option <RayHitpoint>(new RayHitpoint(hitPoint, normal, temp)));
}
return(Option <RayHitpoint> .Empty);
}
private static Vector3 GetNormalAtPoint(Vector3 point, PositionableSphere sphereEntity)
{
var(positionable, sphere) = sphereEntity;
return((point - positionable.Translation) / sphere.Radius);
}
public Bounds Compute(PositionableSphere positionableSphere)
{
var(positionable, sphere1) = positionableSphere;
return(new Bounds(positionable.Translation - new Vector3(sphere1.Radius),
positionable.Translation + new Vector3(sphere1.Radius)));
}
public HitableSphere(PositionableSphere sphere, IHitableSphereComputer computer)
{
_sphere = sphere;
_computer = computer;
}