diff --git a/.gitmodules b/.gitmodules
index 2baec20..d781ec1 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,6 +1,3 @@
-[submodule "subprojects/philox"]
-	path = subprojects/philox
-	url = git@github.com:MorizzG/philox
 [submodule "subprojects/rand"]
 	path = subprojects/rand
 	url = git@github.com:MorizzG/rand
diff --git a/meson.build b/meson.build
index dbf7d53..350c2b6 100644
--- a/meson.build
+++ b/meson.build
@@ -12,9 +12,24 @@ add_project_arguments(
     language : 'cpp'
 )
 
+if get_option('native')
+    add_global_arguments(
+        '-march=native',
 
-philox_proj = subproject('philox', default_options : ['warning_level=0', 'werror=false'])
-philox_dep = philox_proj.get_variable('philox_dep')
+        language : 'c'
+    )
+
+    add_global_arguments(
+        '-march=native',
+
+        language : 'cpp'
+    )
+endif
+
+
+
+rand_proj = subproject('rand', default_options : ['warning_level=0', 'werror=false'])
+rand_dep = rand_proj.get_variable('rand_dep')
 
 
 sources = []
@@ -22,4 +37,4 @@ subdir('src')
 
 inc = include_directories('src')
 
-executable('ray-tracer', sources, include_directories : inc, dependencies : [philox_dep])
+executable('ray-tracer', sources, include_directories : inc, dependencies : [rand_dep])
diff --git a/meson.options b/meson.options
new file mode 100644
index 0000000..a909bad
--- /dev/null
+++ b/meson.options
@@ -0,0 +1 @@
+option('native', type : 'boolean', value : true)
diff --git a/perf.data b/perf.data
new file mode 100644
index 0000000..2796874
Binary files /dev/null and b/perf.data differ
diff --git a/perf.data.old b/perf.data.old
new file mode 100644
index 0000000..3090232
Binary files /dev/null and b/perf.data.old differ
diff --git a/src/colour.h b/src/colour.h
index 47d57ee..c34d3f8 100644
--- a/src/colour.h
+++ b/src/colour.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <cassert>
+#include <cmath>
 #include <iomanip>
 #include <ios>
 #include <iostream>
@@ -43,6 +44,10 @@ class Colour {
         return *this;
     }
 
+    constexpr Colour to_gamma2() const {
+        return Colour{std::sqrt(r()), std::sqrt(g()), std::sqrt(b())};
+    }
+
     std::string to_string() const {
         std::stringstream ss;
 
@@ -74,8 +79,12 @@ constexpr Colour operator+(Colour c1, Colour c2) {
     return out;
 }
 
-inline std::ostream& operator<<(std::ostream& os, Colour colour) {
-    os << FToU8(colour.r()) << ' ' << FToU8(colour.g()) << ' ' << FToU8(colour.b());
+inline std::ostream& operator<<(std::ostream& os, Colour c) {
+    double r = c.r();
+    double g = c.g();
+    double b = c.b();
+
+    os << FToU8(r) << ' ' << FToU8(g) << ' ' << FToU8(b);
 
     return os;
 }
diff --git a/src/image.h b/src/image.h
index 39a4e92..79a3d86 100644
--- a/src/image.h
+++ b/src/image.h
@@ -52,18 +52,15 @@ constexpr std::ostream& operator<<(std::ostream& os, const Image& img) {
     os << "255" << newline;
 
     for (u32 j = 0; j < img.height(); j++) {
-        std::clog << "\rWriting line " << j << " of " << img.height() << std::flush;
-
         for (u32 i = 0; i < img.width(); i++) {
             const Colour col = img[i, j];
 
             col.CheckValid();
 
-            os << col << newline;
+            // apply gamma 2 transform
+            os << col.to_gamma2() << newline;
         }
     }
 
-    std::clog << "\rDone                                                " << newline;
-
     return os;
 }
diff --git a/src/main.cc b/src/main.cc
index fc81e8c..3ed7bcf 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -2,10 +2,11 @@
 #include <memory>
 
 #include "camera.h"
+#include "colour.h"
 #include "image.h"
+#include "material.h"
 #include "raytracer.h"
 #include "renderer.h"
-#include "renderobject.h"
 #include "renderobjectlist.h"
 #include "sphere.h"
 #include "vec3.h"
@@ -15,14 +16,16 @@ int main(int /* argc */, char* /* argv */[]) {
 
     RenderObjectList world;
 
-    world.Add(std::make_shared<Sphere>(Vec3{0, -100.5, -1}, 100));
-    world.Add(std::make_shared<Sphere>(-Vec3::e_z, 0.5));
+    auto lamb = std::make_shared<Lambertian>(Colour{0.1, 0.4, 0.8});
+
+    world.Add(std::make_unique<Sphere>(Vec3{0, -100.5, -1}, 100, lamb));
+    world.Add(std::make_unique<Sphere>(-Vec3::e_z, 0.5, lamb));
 
     // camera
 
     constexpr f64 aspect_ratio = 16.0 / 9.0;
 
-    constexpr u32 image_width = 800;
+    constexpr u32 image_width = 600;
     constexpr auto image_height = static_cast<u32>(image_width / aspect_ratio);
 
     // constexpr u32 image_width = 1920;
diff --git a/src/material.h b/src/material.h
new file mode 100644
index 0000000..bbedc27
--- /dev/null
+++ b/src/material.h
@@ -0,0 +1,52 @@
+#pragma once
+
+#include <optional>
+#include <tuple>
+
+#include "colour.h"
+#include "rand.h"
+#include "ray.h"
+#include "renderobject.h"
+
+class Material {
+   public:
+    constexpr Material() = default;
+
+    constexpr Material(const Material&) = default;
+    Material& operator=(const Material&) = default;
+
+    constexpr Material(Material&&) = default;
+    Material& operator=(Material&&) = default;
+
+    virtual ~Material() = default;
+
+    RandomGen& rand() const { return rand_; }
+
+    virtual std::optional<std::tuple<Colour, Ray>> Scatter(const Ray& in,
+                                                           const HitRecord& hit_record) const = 0;
+
+   private:
+    mutable RandomGen rand_{};
+};
+
+class Lambertian : public Material {
+   public:
+    constexpr explicit Lambertian(Colour albedo) : albedo_{albedo} {}
+
+    std::optional<std::tuple<Colour, Ray>> Scatter(const Ray& /* in */,
+                                                   const HitRecord& hit_record) const override {
+        auto scatter_dir = hit_record.normal + rand().GenOnUnitSphere();
+
+        // TODO: enable
+        /* if (scatter_dir.almost_zero()) {
+            scatter_dir = hit_record.normal;
+        } */
+
+        Ray scattered{hit_record.p, scatter_dir};
+
+        return std::make_tuple(albedo_, scattered);
+    }
+
+   private:
+    Colour albedo_;
+};
diff --git a/src/raytracer.h b/src/raytracer.h
index 40fccf2..32f9d67 100644
--- a/src/raytracer.h
+++ b/src/raytracer.h
@@ -10,6 +10,8 @@ using u64 = uint64_t;
 using f64 = double;
 
 constexpr f64 kInf = std::numeric_limits<f64>::infinity();
+constexpr f64 kNan = std::numeric_limits<f64>::signaling_NaN();
+
 constexpr f64 kPi = std::numbers::pi_v<f64>;
 
 constexpr char newline = '\n';
diff --git a/src/renderer.h b/src/renderer.h
index c534af5..4aab1ba 100644
--- a/src/renderer.h
+++ b/src/renderer.h
@@ -1,11 +1,15 @@
 #pragma once
 
+#include <array>
+#include <cassert>
 #include <iostream>
+#include <thread>
 
 #include "camera.h"
 #include "colour.h"
 #include "image.h"
 #include "interval.h"
+#include "material.h"
 #include "rand.h"
 #include "ray.h"
 #include "raytracer.h"
@@ -14,28 +18,52 @@
 
 class Renderer {
    public:
-    constexpr explicit Renderer(Camera camera, u32 samples_per_pixel = 10)
-        : camera_{camera}, samples_per_pixel_{samples_per_pixel} {}
+    constexpr explicit Renderer(Camera camera, u32 samples_per_pixel = 100, u32 max_bounces = 50)
+        : camera_{camera}, samples_per_pixel_{samples_per_pixel}, max_bounces_{max_bounces} {}
 
-    constexpr Image Render(const RenderObject& world) {
+    constexpr u32& samples_per_pixel() { return samples_per_pixel_; }
+    constexpr u32 samples_per_pixel() const { return samples_per_pixel_; }
+
+    constexpr u32& max_bounces() { return max_bounces_; }
+    constexpr u32 max_bounces() const { return max_bounces_; }
+
+    Image Render(const RenderObject& world) {
         Image img{camera_.image_width(), camera_.image_height()};
 
-        for (u32 j = 0; j < img.height(); j++) {
-            std::clog << "\rWriting line " << j << " of " << img.height() << std::flush;
+        constexpr u32 kNumThreads = 4;
 
-            for (u32 i = 0; i < img.width(); i++) {
-                Colour colour_sum{0.0, 0.0, 0.0};
+        auto render_thread = [this, &world, &img](u32 thread) {
+            for (u32 j = thread; j < img.height(); j += kNumThreads) {
+                std::clog << "\rWriting line " << j << " of " << img.height() << std::flush;
 
-                for (u32 num_sample = 0; num_sample < samples_per_pixel_; num_sample++) {
-                    auto ray = SampleRay(i, j);
+                for (u32 i = 0; i < img.width(); i++) {
+                    Colour colour_sum{0.0, 0.0, 0.0};
 
-                    colour_sum += Cast(ray, world);
+                    for (u32 num_sample = 0; num_sample < samples_per_pixel_; num_sample++) {
+                        auto ray = SampleRay(i, j);
+
+                        colour_sum += Cast(ray, world, max_bounces_);
+                    }
+
+                    img[i, j] = colour_sum / samples_per_pixel_;
                 }
-
-                img[i, j] = colour_sum / samples_per_pixel_;
             }
+        };
+
+        // render_thread(0);
+
+        std::array<std::thread, kNumThreads> render_threads;
+
+        for (u32 i = 0; i < kNumThreads; i++) {
+            render_threads[i] = std::thread{render_thread, i};
         }
 
+        for (auto& t : render_threads) {
+            t.join();
+        }
+
+        std::clog << "\rDone                                                " << newline;
+
         return img;
     }
 
@@ -53,22 +81,29 @@ class Renderer {
         return Ray{camera_.centre(), ray_direction};
     }
 
-    constexpr Colour Cast(const Ray& ray, const RenderObject& world) {
-        auto hit_record = world.hit(ray, Interval::kPositive);
+    constexpr Colour Cast(const Ray& ray, const RenderObject& world, u32 bounces) {
+        auto hit_record = world.hit(ray, Interval{0.001, kInf});
 
         if (hit_record.has_value()) {
-            Vec3 normal = hit_record->normal;
-
-            if (!hit_record->front_face) {
+            if (!hit_record->front_face || bounces == 0) {
                 return Colour::kBlack;
             }
 
+            /* Vec3 normal = hit_record->normal;
+
             Vec3 new_origin = hit_record->p;
-            Vec3 new_direction = rand_.GenOnHemisphere(normal);
 
-            Ray new_ray{new_origin, new_direction};
+            // Vec3 new_direction = rand_.GenOnHemisphere(normal);
+            Vec3 new_direction = normal + rand_.GenOnUnitSphere();
 
-            return 0.5 * Cast(new_ray, world);
+            Ray new_ray{new_origin, new_direction}; */
+
+            auto res = hit_record->mat->Scatter(ray, hit_record.value());
+
+            auto [albedo, out_ray] = res.value();
+
+            assert(bounces > 0);
+            return 0.5 * Cast(out_ray, world, bounces - 1);
         }
 
         auto unit_dir = ray.direction().normed();
@@ -83,4 +118,5 @@ class Renderer {
     RandomGen rand_{};
 
     u32 samples_per_pixel_;
+    u32 max_bounces_;
 };
diff --git a/src/renderobject.h b/src/renderobject.h
index 70ab0c1..8829e6f 100644
--- a/src/renderobject.h
+++ b/src/renderobject.h
@@ -5,12 +5,17 @@
 
 #include "interval.h"
 #include "ray.h"
+#include "raytracer.h"
 #include "vec3.h"
 
+class Material;
+
 struct HitRecord {
     Point3 p;
     Vec3 normal;
-    f64 t = 0.0;
+    const Material* mat = nullptr;
+
+    f64 t = kNan;
     bool front_face = true;
 };
 
diff --git a/src/renderobjectlist.h b/src/renderobjectlist.h
index e716086..3597942 100644
--- a/src/renderobjectlist.h
+++ b/src/renderobjectlist.h
@@ -1,18 +1,21 @@
 #pragma once
 
 #include <initializer_list>
+#include <memory>
 #include <optional>
+#include <utility>
 #include <vector>
 
 #include "interval.h"
 #include "ray.h"
+#include "raytracer.h"
 #include "renderobject.h"
 
 class RenderObjectList : public RenderObject {
    public:
     constexpr RenderObjectList() = default;
     // explicit RenderObjectList(const SharedRenderObject& obj) { Append(obj); }
-    RenderObjectList(std::initializer_list<SharedRenderObject> objs) : objs_{objs} {}
+    // RenderObjectList(std::initializer_list<RenderObject> objs) : objs_{objs} {}
 
     constexpr auto begin() { return objs_.begin(); }
     constexpr auto end() { return objs_.end(); }
@@ -20,7 +23,7 @@ class RenderObjectList : public RenderObject {
     constexpr auto begin() const { return objs_.begin(); }
     constexpr auto end() const { return objs_.end(); }
 
-    void Add(const SharedRenderObject& obj) { objs_.push_back(obj); }
+    void Add(std::unique_ptr<RenderObject> obj) { objs_.emplace_back(std::move(obj)); }
 
     void Clear() { objs_.clear(); }
 
@@ -43,5 +46,5 @@ class RenderObjectList : public RenderObject {
     }
 
    private:
-    std::vector<SharedRenderObject> objs_;
+    std::vector<std::unique_ptr<RenderObject>> objs_;
 };
diff --git a/src/sphere.h b/src/sphere.h
index 852dd5f..f968b76 100644
--- a/src/sphere.h
+++ b/src/sphere.h
@@ -2,9 +2,11 @@
 
 #include <cassert>
 #include <cmath>
+#include <memory>
 #include <optional>
 
 #include "interval.h"
+#include "material.h"
 #include "ray.h"
 #include "raytracer.h"
 #include "renderobject.h"
@@ -13,7 +15,9 @@
 class Sphere : public RenderObject {
    public:
     constexpr Sphere() = default;
-    constexpr Sphere(Point3 centre, f64 radius) : centre_{centre}, radius_{radius} {
+
+    Sphere(Point3 centre, f64 radius, const std::shared_ptr<Material>& mat)
+        : centre_{centre}, radius_{radius}, mat_{mat} {
         assert(radius >= 0);
     }
 
@@ -21,7 +25,7 @@ class Sphere : public RenderObject {
     constexpr f64 radius() const { return radius_; }
 
     std::optional<HitRecord> hit(const Ray& ray, Interval ts) const override {
-        HitRecord hit_record;
+        HitRecord hit_record{};
 
         Vec3 oc = ray.origin() - centre_;
 
@@ -66,6 +70,7 @@ class Sphere : public RenderObject {
 
         hit_record.t = t;
         hit_record.p = ray.At(t);
+        hit_record.mat = mat_.get();
 
         if (hit_record.front_face) {
             hit_record.normal = (hit_record.p - centre_) / radius_;
@@ -79,4 +84,6 @@ class Sphere : public RenderObject {
    private:
     Point3 centre_{};
     f64 radius_ = 0.0;
+
+    std::shared_ptr<Material> mat_;
 };
diff --git a/src/vec3.h b/src/vec3.h
index 5d4794e..5f7520a 100644
--- a/src/vec3.h
+++ b/src/vec3.h
@@ -59,6 +59,12 @@ class Vec3 {
         return *this;
     }
 
+    constexpr bool almost_zero() const {
+        f64 eps = 1e-8;
+
+        return std::fabs(x()) < eps && std::fabs(y()) < eps && std::fabs(z()) < eps;
+    }
+
     constexpr f64 squared() const { return x() * x() + y() * y() + z() * z(); }
 
     constexpr f64 norm() const { return std::sqrt(squared()); }
diff --git a/subprojects/philox b/subprojects/philox
deleted file mode 160000
index cf69284..0000000
--- a/subprojects/philox
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit cf69284bd2d82b279c34fb1cf90543fd04b3a038
diff --git a/subprojects/rand b/subprojects/rand
index 4d76806..8043050 160000
--- a/subprojects/rand
+++ b/subprojects/rand
@@ -1 +1 @@
-Subproject commit 4d7680624857241aca166f58b957712b0583fa05
+Subproject commit 8043050d3c871d241a1274be81bfaf1894f5edb2