public Color Shade(Ray ray, Scene scene, int depth)
{
if (depth == 0)
{
var ambient = scene.AmbientLight.Color;
return(new Color(ambient.R, ambient.G, ambient.B));
}
HitInfo hitInfo = new HitInfo();
if (scene.HitTest(ray, ref hitInfo, 0.001f, float.PositiveInfinity))
{
var emitted =
hitInfo.ModelHit.Material.Emitted(hitInfo.TexCoord.X, hitInfo.TexCoord.Y);
if (hitInfo.ModelHit.Material.Scatter(ref ray, ref hitInfo, out Color attenuation, out Ray scattered))
{
return(emitted + attenuation * Shade(scattered, scene, depth - 1));
}
return(emitted);
}
return(scene.AmbientLight.Color);
}
public override void Render(Scene scene, Camera camera)
{
scene.Preprocess();
if (camera is LensCamera lensCamera && lensCamera.AutoFocus)
{
var ray = lensCamera.GetRay(0.5f, 0.5f);
var hitInfo = new HitInfo();
var hit = scene.HitTest(ray, ref hitInfo, 0.001f, float.PositiveInfinity);
if (hit)
{
lensCamera.FocusDistance = hitInfo.Distance;
}
else
{
lensCamera.FocusDistance = 100000f;
}
}
int width = Resolution;
int height = (int)(width / camera.AspectRatio);
var image = new Texture(width, height);
AbstractSampler <Vector2> sampler = new ThreadSafeSampler <Vector2>(Sampling, Samples);
for (int k = 0; k < Samples; k++)
{
try
{
Parallel.For(0, width, new ParallelOptions {
CancellationToken = CancellationToken
}, i =>
{
for (int j = 0; j < height; j++)
{
var sample = sampler.GetSample(k);
float u = (i + sample.X) / (width - 1);
float v = (j + sample.Y) / (height - 1);
Ray ray = camera.GetRay(u, v);
var shade = Shade(ray, scene, MaxDepth);
image.Bloom(shade, i, j, (int)shade.GetBrightness(), Bloom);
image[i, j] += shade;
}
});
}
catch (Exception e)
{
Log.Warn(e);
}
if (CancellationToken.IsCancellationRequested)
{
return;
}
if (k % SamplesRenderStep == 0 || k == Samples - 1)
{
var output = new Texture(image);
output.Process(c => (c / (k + 1)).Clamp());
if (GammaCorrection)
{
output.AutoGammaCorrect();
}
var percentage = (k + 1) * 100 / Samples;
OnFrameReady?.Invoke(percentage, output);
}
}
}
private Color Trace(ref Ray ray, Scene scene, int depth)
{
HitTestResult hittest = scene.HitTest(ref ray);
if (hittest == null)
{
return(Color.Black);
}
var d = hittest.Ray.Direction;
var pos = hittest.Distance * hittest.Ray.Direction + hittest.Ray.Position; //交点位置
var normal = hittest.Shape.GetNormal(pos); //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.Specular(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 = (float)(((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 = ((float)(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);
}
