public override bool Hit(Ray ray, float t_min, float t_max, ref HitRecord record)
{
//平面的隐式方程 p·n = d
//射线方程 p = o + t·dir
//代入有 t = (d - o·n)/(dir·n)
//考虑到只有射向平面才叫相交(射出不算),所以必须满足 Vec.dot(dir, normal) < 0
float dir_dot_normal = Vec3.dot(ray.Direction, normal);
if (dir_dot_normal < 0)
{
float t = (d - Vec3.dot(ray.Origin, normal)) / dir_dot_normal;
if (t > t_min && t < t_max)
{
if (record == null)
{
record = new HitRecord();
}
record.t = t;
record.hit_point = ray.GetPoint(t);
record.normal = normal;
record.material = material;
return(true);
}
}
return(false);
}
public override Ray GetScatteredRay(Ray ray_in, HitRecord record)
{
//镜面反射...
Vec3 scattered_dir = ray_in.Direction - 2 * Vec3.dot(ray_in.Direction, record.normal) * record.normal;
return(new Ray(record.hit_point, scattered_dir, ray_in.DeltaTime));
}
public override Vec3 GetColor(BaseLight light, Ray view_ray, HitRecord record, float depth)
{
//Phong公式: L = Kd * I * max(0, n·l) + Ks * I * max(0, n·h)^p
// Kd是散射系数, n是表面法向量,l是光源方向(从相交点指向光源), Ks是高光系数,h是v+l的单位向量,v是视线反方向(从相交点只想视点), I是光强(光在这一点的颜色)
Vec3 l = -(light.GetLightRay(record.hit_point, view_ray.DeltaTime).Direction.normalize());
float n_dot_l = Math.Max(0, Vec3.dot(record.normal, l));
Vec3 h = (-view_ray.Direction + l).normalize();
float n_dot_h = Math.Max(0, Vec3.dot(record.normal, h));
Vec3 I = Vec3.one;
Vec3 dif = diffuse * n_dot_l;
Vec3 spe = specular * (float)Math.Pow(n_dot_h, phong_exp);
spe *= _smoothstep(0, 0.12f, n_dot_l);//为了解决背光面高光的问题,如果n_dot_l<0直接spe=0会有颜色间断层,需要做插值处理
Vec3 L = Vec3.product(I, dif + spe);
//上面有两个bug/疑问
//(1)背光面也能出现高光,因为公式里n·l<0并不影响 Ks * I * max(0, n·h)^p的值;
//(2)求出来的L超过(1,1,1)范围了.---暂时强行映射到[0,1]
//上面两个问题估计都是要改diffuse和specular来处理
//目前先特殊处理下,以后看看大佬们怎么搞的
return(L);
}
public override Vec3 GetColor(BaseLight light, Ray view_ray, HitRecord record, float depth)
{
Vec3 l = -(light.GetLightRay(record.hit_point, view_ray.DeltaTime).Direction.normalize());
float n_dot_l = Math.Max(0, Vec3.dot(record.normal, l));
Vec3 I = Vec3.one;
Vec3 dif = diffuse * n_dot_l;
Vec3 L = Vec3.product(I, dif);
return(L);
}
public override bool Hit(Ray ray, float t_min, float t_max, ref HitRecord record)
{
//运动的球先求出time时刻球心位置
Vec3 _center = GetCenter(ray.DeltaTime);
//ray == o+t*d; o 是射线原点,t是参数,d是方向
//(p - c)^2 = radius^2;p是球面上一点,c是球心,radius是球半径
//交点就是把射线方程代入球面方程化为一元二次方程求参数t
Vec3 p_sub_c = ray.Origin - _center;
float A = Vec3.dot(ray.Direction, ray.Direction);
float B = Vec3.dot(p_sub_c, ray.Direction);//(b^2)/4
float C = Vec3.dot(p_sub_c, p_sub_c) - radius * radius;
float b_square_sub_four_a_c_div_four = B * B - A * C;//(b^2 - 4ac)/4
//方程组有解
if (b_square_sub_four_a_c_div_four > 0)
{
float temp = (-B - (float)Math.Sqrt(b_square_sub_four_a_c_div_four)) / A;// (-b-sqrt(4ac))/2a 分子分母同时除以2就可以得到这个式子,这里的 b=2B
if (temp > t_min && temp < t_max)
{
if (record == null)
{
record = new HitRecord();
}
record.t = temp;
record.hit_point = ray.GetPoint(temp);
record.normal = (record.hit_point - _center).normalize();//球心与球面上一点为法向量方向
record.material = material;
return(true);
}
temp = (-B + (float)Math.Sqrt(b_square_sub_four_a_c_div_four)) / A;
if (temp > t_min && temp < t_max)
{
if (record == null)
{
record = new HitRecord();
}
record.t = temp;
record.hit_point = ray.GetPoint(temp);
record.normal = (record.hit_point - _center).normalize();//球心与球面上一点为法向量方向
record.material = material;
return(true);
}
}
return(false);
}
public override Vec3 GetColor(BaseLight light, Ray view_ray, HitRecord record, float depth)
{
Vec3 l = -(light.GetLightRay(record.hit_point, view_ray.DeltaTime).Direction.normalize());
float n_dot_l = Math.Max(0, Vec3.dot(record.normal, l));
Vec3 I = Vec3.one;
Vec3 color = texture == null ? diffuse : texture.GetColorValue(0, 0, record.hit_point);//这里还要改的，下面的material也是，感觉material用来定义反射之类的物理计算公式。颜色映射还是交给texture吧
Vec3 dif = color * n_dot_l;
Vec3 L = Vec3.product(I, dif);
return(L);
}
private float PerlinInterp(Vec3[][][] c, float u, float v, float w)
{
float uu = u * u * (3 - 2 * u);
float vv = v * v * (3 - 2 * v);
float ww = w * w * (3 - 2 * w);
float accum = 0;
for (int i = 0; i < 2; i++)
{
for (int j = 0; j < 2; j++)
{
for (int k = 0; k < 2; k++)
{
Vec3 weight_v = new Vec3(u - i, v - j, w - k);
accum +=
(i * uu + (1 - i) * (1 - uu)) *
(j * vv + (1 - j) * (1 - vv)) *
(k * ww + (1 - k) * (1 - ww)) *
Vec3.dot(c[i][j][k], weight_v);
}
}
}
return(accum);
}