public override bool HitTest(ref Ray ray, ref HitTestResult result)
{
Vector eo = Center;
eo.Sub(ref ray.Position);
double v = Vector.Dot(ref eo, ref ray.Direction);
var disc = Radius * Radius - Vector.Dot(ref eo, ref eo) + v * v;
if (disc < 0)
{
return(false);
}
disc = v - Math.Sqrt(disc);
if (disc < 0.001f)
{
return(false);
}
result.Shape = this;
result.Position = ray.Position + ray.Direction * disc;
result.Normal = result.Position - Center;
result.Normal.Normalize();
result.Distance = disc;
return(true);
}
public abstract bool HitTest(ref Ray ray, ref HitTestResult result);
private Color Trace(ref Ray ray, Scene scene, int depth)
{
HitTestResult hittest = new HitTestResult();
hittest.Distance = double.MaxValue;
if (!scene.HitTest(ref ray, ref hittest))
{
return(Color.Black);
}
var d = ray.Direction;
var pos = hittest.Distance * ray.Direction + ray.Position; //交点位置
var normal = hittest.Normal; //交点法向量
var cosa = normal * d; //-Cos(入射角)
var reflectDir = d - 2 * cosa * normal; //反射方向
Color color;
if (cosa < 0)
{
color = GetNaturalColor(hittest.Shape, ref pos, ref normal, ref reflectDir, scene);
}
else
{
color = Color.Black;
}
if (depth <= 0)
{
return(color);
}
depth--;
//追踪反射光线
var ray1 = new Ray(pos, reflectDir);
var rcolor1 = Trace(ref ray1, scene, depth);
rcolor1.Multiply(hittest.Shape.Surface.Reflect(pos));
//追踪折射光线
var n = hittest.Shape.Surface.Refraction(pos);// 折射率
if (n > 0)
{
if (cosa > 0)
{
n = 1 / n;
}
var f = Math.Acos(-cosa); //入射角
var t = Math.Asin(Math.Sqrt(1 - cosa * cosa)); //折射角
//fresnel公式，计算反射比
double s1 = Math.Sin(f - t);
double s2 = Math.Sin(f + t);
double t1 = Math.Tan(f - t);
double t2 = Math.Tan(f + t);
var factor = (((s1 * s1) / (s2 * s2) + (t1 * t1) / (t2 * t2)) / 2);
if (factor < 1 && factor >= 0) //等于1时发生了全反射
{
rcolor1.Multiply(factor);
//折射定律矢量形式：n2 * e2 - n1 * e1 = (n2 * cos(t) - n1 * cos(f)) * normal
var dir = ((n * Math.Cos(t) - Math.Cos(f)) * normal) * (1 / n);
dir.Normalize();
var ray2 = new Ray(pos, dir);
var rcolor2 = Trace(ref ray2, scene, depth);
rcolor2.Multiply(1 - factor);
color.Add(ref rcolor2);
}
}
color.Add(ref rcolor1);
return(color);
}
