// вычисление локальной модели освещения
public Point3D shade(Point3D hit_point, Point3D normal, Point3D color_obj, float diffuse_coef)
{
Point3D dir = point_light - hit_point;
dir = Point3D.norm(dir); // направление луча из источника света в точку удара
Point3D diff = diffuse_coef * color_light * Math.Max(Point3D.scalar(normal, dir), 0);
return(new Point3D(diff.x * color_obj.x, diff.y * color_obj.y, diff.z * color_obj.z));
}
// преломление
public Ray refract(Point3D hit_point, Point3D normal, float eta)
{
Ray res_ray = new Ray();
float sclr = Point3D.scalar(normal, direction);
float k = 1 - eta * eta * (1 - sclr * sclr);
if (k >= 0)
{
float cos_theta = (float)Math.Sqrt(k);
res_ray.start = new Point3D(hit_point);
res_ray.direction = Point3D.norm(eta * direction - (cos_theta + eta * sclr) * normal);
return(res_ray);
}
else
{
return(null);
}
}
public bool ray_intersects_triangle(Ray r, Point3D p0, Point3D p1, Point3D p2, out float intersect)
{
intersect = -1;
Point3D edge1 = p1 - p0;
Point3D edge2 = p2 - p0;
Point3D h = r.direction * edge2;
float a = Point3D.scalar(edge1, h);
if (a > -EPS && a < EPS)
{
return(false); // This ray is parallel to this triangle.
}
float f = 1.0f / a;
Point3D s = r.start - p0;
float u = f * Point3D.scalar(s, h);
if (u < 0 || u > 1)
{
return(false);
}
Point3D q = s * edge1;
float v = f * Point3D.scalar(r.direction, q);
if (v < 0 || u + v > 1)
{
return(false);
}
// At this stage we can compute t to find out where the intersection point is on the line.
float t = f * Point3D.scalar(edge2, q);
if (t > EPS)
{
intersect = t;
return(true);
}
else // This means that there is a line intersection but not a ray intersection.
{
return(false);
}
}
public static bool ray_sphere_intersection(Ray r, Point3D sphere_pos, float sphere_rad, out float t)
{
Point3D k = r.start - sphere_pos;
float b = Point3D.scalar(k, r.direction);
float c = Point3D.scalar(k, k) - sphere_rad * sphere_rad;
float d = b * b - c;
t = 0;
if (d >= 0)
{
float sqrtd = (float)Math.Sqrt(d);
float t1 = -b + sqrtd;
float t2 = -b - sqrtd;
float min_t = Math.Min(t1, t2);
float max_t = Math.Max(t1, t2);
t = (min_t > EPS) ? min_t : max_t;
return(t > EPS);
}
return(false);
}
// отражение
public Ray reflect(Point3D hit_point, Point3D normal)
{
Point3D reflect_dir = direction - 2 * normal * Point3D.scalar(direction, normal);
return(new Ray(hit_point, hit_point + reflect_dir));
}
public Point3D RayTrace(Ray r, int iter, float env)
{
if (iter <= 0)
{
return(new Point3D(0, 0, 0));
}
float t = 0; // позиция точки пересечения луча с фигурой на луче
Point3D normal = null;
Material m = new Material();
Point3D res_color = new Point3D(0, 0, 0);
bool refract_out_of_figure = false; // луч преломления выходит из объекта?
foreach (Figure fig in scene)
{
if (fig.figure_intersection(r, out float intersect, out Point3D n))
{
if (intersect < t || t == 0) // нужна ближайшая фигура к точке наблюдения
{
t = intersect;
normal = n;
m = new Material(fig.figure_material);
}
}
}
if (t == 0)
{
return(new Point3D(0, 0, 0));
}
//если угол между нормалью к поверхности объекта и направлением луча положительный, => угол острый, => луч выходит из объекта в среду
if (Point3D.scalar(r.direction, normal) > 0)
{
normal *= -1;
refract_out_of_figure = true;
}
Point3D hit_point = r.start + r.direction * t;
foreach (Light l in lights)
{
Point3D amb = l.color_light * m.ambient;
amb.x = (amb.x * m.clr.x);
amb.y = (amb.y * m.clr.y);
amb.z = (amb.z * m.clr.z);
res_color += amb;
// диффузное освещение
if (is_visible(l.point_light, hit_point))
{
res_color += l.shade(hit_point, normal, m.clr, m.diffuse);
}
}
if (m.reflection > 0)
{
Ray reflected_ray = r.reflect(hit_point, normal);
res_color += m.reflection * RayTrace(reflected_ray, iter - 1, env);
}
if (m.refraction > 0)
{
float eta; //коэффициент преломления
if (refract_out_of_figure) //луч выходит в среду
{
eta = m.environment;
}
else
{
eta = 1 / m.environment;
}
Ray refracted_ray = r.refract(hit_point, normal, eta);
if (refracted_ray != null)
{
res_color += m.refraction * RayTrace(refracted_ray, iter - 1, m.environment);
}
}
return(res_color);
}