internal void Render(Scene scene, bool parallel)
{
    int[] rgb = new int[screenWidth * screenHeight];
    var pixelsQuery = from y in Enumerable.Range(0, screenHeight).AsParallel().WithDegreeOfParallelism(parallel ? 2 : 1)
                      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)) };
    int rowsProcessed = 0;
    pixelsQuery.ForAll(row =>
        {
            foreach (var pixel in row)
            {
                rgb[pixel.X + (pixel.Y * screenWidth)] = pixel.Color.ToInt32();
            }
            int processed = Interlocked.Increment(ref rowsProcessed);
            if (processed % rowsPerUpdate == 0 ||
                processed >= screenHeight) updateImageHandler(rgb);
        });
}