// dot(rayDir, rayDir) * t^2 + 2*t*dot(rayDir, rayOrig-center) + dot(rayOrig-center, rayOrig-center) - R*R=0
public bool Hit(Ray ray, float tMin, float tMax, ref HitRecord record)
{
float a = ray.Direction.LengthSquared; // dot(rayDir, rayDir)
Vec3 temp = new Vec3();
Vec3.Subtract(ray.Origin, this.Center, temp);
float b = 2 * ray.Direction.Dot(temp); //2*dot(rayDir, rayOrig-center)
float c = temp.LengthSquared - this.Radius * this.Radius; //dot(rayOrig-center, rayOrig-center) - R*R
if (!PolyUtils.HasRealRoot(a, b, c))
{
// No hit
return(false);
}
// Check first root for hit
float firstRoot = PolyUtils.FirstRoot(a, b, c);
if (firstRoot > tMin && firstRoot < tMax)
{
record.T = firstRoot;
record.Point = ray.PointAt(firstRoot);
Vec3.Subtract(record.Point, this.Center, temp);
record.Normal = temp / this.Radius;
record.Material = this.Material;
return(true);
}
// Check second root for hit
float secondRoot = PolyUtils.SecondRoot(a, b, c);
if (secondRoot > tMin && secondRoot < tMax)
{
record.T = secondRoot;
record.Point = ray.PointAt(secondRoot);
Vec3.Subtract(record.Point, this.Center, temp);
record.Normal = temp / this.Radius;
record.Material = this.Material;
return(true);
}
return(false);
}
