В блоге Мигеля де Иказы выложена реализация алгоритма трассировки лучей в виде ОДНОГО LINQ выражения. Вот как выглядит это чудо:

var pixelsQuery =
    from y in Enumerable.Range(0, screenHeight)
    let recenterY = -(y - (screenHeight / 2.0)) / (2.0 * screenHeight)
    select from x in Enumerable.Range(0, screenWidth)
           let recenterX = (x - (screenWidth / 2.0)) / (2.0 * screenWidth)
           let point =
               Vector.Norm(Vector.Plus(scene.Camera.Forward,
                                       Vector.Plus(Vector.Times(recenterX, scene.Camera.Right),
                                                   Vector.Times(recenterY, scene.Camera.Up))))
           let ray = new Ray() { Start = scene.Camera.Pos, Dir = point }
           let computeTraceRay = (Func<Func<TraceRayArgs, Color>, Func<TraceRayArgs, Color>>)
            (f => traceRayArgs =>
             (from isect in
                  from thing in traceRayArgs.Scene.Things
                  select thing.Intersect(traceRayArgs.Ray)
              where isect != null
              orderby isect.Dist
              let d = isect.Ray.Dir
              let pos = Vector.Plus(Vector.Times(isect.Dist, isect.Ray.Dir), isect.Ray.Start)
              let normal = isect.Thing.Normal(pos)
              let reflectDir = Vector.Minus(d, Vector.Times(2 * Vector.Dot(normal, d), normal))
              let naturalColors =
                  from light in traceRayArgs.Scene.Lights
                  let ldis = Vector.Minus(light.Pos, pos)
                  let livec = Vector.Norm(ldis)
                  let testRay = new Ray() { Start = pos, Dir = livec }
                  let testIsects = from inter in
                                       from thing in traceRayArgs.Scene.Things
                                       select thing.Intersect(testRay)
                                   where inter != null
                                   orderby inter.Dist
                                   select inter
                  let testIsect = testIsects.FirstOrDefault()
                  let neatIsect = testIsect == null ? 0 : testIsect.Dist
                  let isInShadow = !((neatIsect > Vector.Mag(ldis)) || (neatIsect == 0))
                  where !isInShadow
                  let illum = Vector.Dot(livec, normal)
                  let lcolor = illum > 0 ? Color.Times(illum, light.Color) : Color.Make(0, 0, 0)
                  let specular = Vector.Dot(livec, Vector.Norm(reflectDir))
                  let scolor = specular > 0
                                 ? Color.Times(Math.Pow(specular, isect.Thing.Surface.Roughness),
                                               light.Color)
                                 : Color.Make(0, 0, 0)
                  select Color.Plus(Color.Times(isect.Thing.Surface.Diffuse(pos), lcolor),
                                    Color.Times(isect.Thing.Surface.Specular(pos), scolor))
              let reflectPos = Vector.Plus(pos, Vector.Times(.001, reflectDir))
              let reflectColor = traceRayArgs.Depth >= MaxDepth
                                  ? Color.Make(.5, .5, .5)
                                  : Color.Times(isect.Thing.Surface.Reflect(reflectPos),
                                                f(new TraceRayArgs(new Ray()
                                                {
                                                    Start = reflectPos,
                                                    Dir = reflectDir
                                                },
                                                                   traceRayArgs.Scene,
                                                                   traceRayArgs.Depth + 1)))
              select naturalColors.Aggregate(reflectColor,
                                             (color, natColor) => Color.Plus(color, natColor))
             ).DefaultIfEmpty(Color.Background).First())
           let traceRay = Y(computeTraceRay)
           select new { X = x, Y = y, Color = traceRay(new TraceRayArgs(ray, scene, 0)) };

foreach (var row in pixelsQuery)
    foreach (var pixel in row)
        setPixel(pixel.X, pixel.Y, pixel.Color.ToDrawingColor());

Там же есть ссылка на файл с полными исходниками.