moved rendering code into own class

implemented antialiasing using random subsampling

src/rand.h

@@ -0,0 +1,47 @@
+#pragma once
+
+#include <cassert>
+
+#include "raytracer.h"
+class Random {
+   public:
+    constexpr explicit Random(u64 j) {
+        assert(j != v_);
+
+        u_ = j ^ v_;
+        GenU64();
+
+        v_ = u_;
+        GenU64();
+
+        w_ = v_;
+        GenU64();
+    }
+
+    constexpr u64 GenU64() {
+        u_ = u_ * 2862933555777941757ULL + 7046029254386353087ULL;
+
+        v_ ^= v_ >> 17;
+        v_ ^= v_ << 31;
+        v_ ^= v_ >> 8;
+
+        w_ = 4294957665ULL * (w_ & 0xffffffffULL) + (w_ >> 32);
+
+        u64 x = u_ ^ (u_ << 21);
+        x ^= x >> 35;
+        x ^= x << 4;
+
+        return (x + v_) ^ w_;
+    }
+
+    constexpr u32 GenU32() { return static_cast<u32>(GenU64()); }
+
+    constexpr f64 GenF64() { return 5.42101086242752217E-20 * static_cast<f64>(GenU64()); }
+
+    constexpr f64 GenF64(f64 min, f64 max) { return min + (max - min) * GenF64(); }
+
+   private:
+    u64 u_ = 0ULL;
+    u64 v_ = 4101842887655102017ULL;
+    u64 w_ = 1ULL;
+};