diff --git a/src/camera.cc b/src/camera.cc
index 70e4896..532a9e0 100644
--- a/src/camera.cc
+++ b/src/camera.cc
@@ -6,10 +6,10 @@
 #include "spdlog/spdlog.h"
 
 Camera::Camera(const Vector3d &up)
-    : gaze_(Vector3d::Identity()), up_(up), camera_speed_(0.3) {}
+    : gaze_(Vector3d{0, 0, -1}), up_(up), camera_speed_(0.3) {}
 
 Camera::Camera(const Vector3d &up, const float camera_speed)
-    : gaze_(Vector3d{0, 0, 1}), up_(up), camera_speed_(camera_speed) {
+    : gaze_(Vector3d{0, 0, -1}), up_(up), camera_speed_(camera_speed) {
   spdlog::debug("Gaze: ({}, {}, {}), Up: ({}, {}, {})", gaze_.x(), gaze_.y(),
                 gaze_.z(), up_.x(), up_.y(), up_.z());
 }
@@ -20,19 +20,22 @@ void Camera::move(const Point3d &offset) {
 
 void Camera::set_gaze(const Vector3d &gaze) { gaze_ = gaze.normalized(); }
 
+const Point3d &Camera::get_position() const { return position_; }
+
 TransformMatrix Camera::get_view_transform() const {
   // Move camera to origin
-  TransformMatrix m{{1, 0, 0, -position_.x()},
-                    {0, 1, 0, -position_.y()},
-                    {0, 0, 1, -position_.z()},
-                    {0, 0, 0, 1}};
+  TransformMatrix translate{{1, 0, 0, -position_.x()},
+                            {0, 1, 0, -position_.y()},
+                            {0, 0, 1, -position_.z()},
+                            {0, 0, 0, 1}};
   // Adjust to fit xyz
   const Vector3d &x_camera{(gaze_.cross(up_)).normalized()};
-  m = TransformMatrix{{x_camera.x(), x_camera.y(), x_camera.z(), 0},
+  TransformMatrix view_mtx =
+      TransformMatrix{{x_camera.x(), x_camera.y(), x_camera.z(), 0},
                       {up_.x(), up_.y(), up_.z(), 0},
                       {-gaze_.x(), -gaze_.y(), -gaze_.z(), 0},
                       {0, 0, 0, 1}} *
-      m;
+      translate;
 
-  return m;
+  return view_mtx;
 }
diff --git a/src/camera.h b/src/camera.h
index b1ceff9..f5e93a5 100644
--- a/src/camera.h
+++ b/src/camera.h
@@ -9,6 +9,7 @@ public:
   explicit Camera(const Vector3d &up, const float camera_speed);
 
 public:
+  const Point3d &get_position() const;
   TransformMatrix get_view_transform() const;
 
 public:
diff --git a/src/main.cc b/src/main.cc
index 41d913d..7e8ac3d 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -111,7 +111,6 @@ int main(int argc, char *argv[]) {
   MinusRenderer renderer{near, far, fov, aspect_ratio};
   renderer.set_meshes(
       Mesh::load_mesh(obj_path, {{Texture::DiffuseMap, diffuse_map_path}}));
-  renderer.set_lamps({std::make_shared<PointLamp>(Point3d{1, 1, -1}, 6.)});
   TransformMatrix translate{
       {1., 0., 0., 3.}, {0., 1., 0., 3.}, {0., 0., 1., -5.}, {0., 0., 0., 1.}};
   renderer.model_transform(translate);
@@ -179,6 +178,8 @@ int main(int argc, char *argv[]) {
       }
       camera.set_gaze(Vector3d{0, 0, -1});
       renderer.view_transform(camera.get_view_transform());
+      renderer.set_lamps(
+          {std::make_shared<PointLamp>(camera.get_position(), 6.)});
 
       const auto &image = renderer.render(resolution_width, resolution_height);
 
diff --git a/src/minus_renderer.cc b/src/minus_renderer.cc
index e960375..9a361ac 100644
--- a/src/minus_renderer.cc
+++ b/src/minus_renderer.cc
@@ -51,23 +51,19 @@ MinusRenderer::construct_transform(const int resolution_width,
   // Orthographic transform
   const float height = calculate_height(fov_, near_);
   const float width = calculate_width(height, aspect_ratio_);
-  const float right = width * 0.5;
-  const float left = -right;
-  const float top = height * 0.5;
-  const float bottom = -top;
 
   const TransformMatrix &ortho_transform =
-      TransformMatrix{{2 / (right - left), 0, 0, 0},
-                      {0, 2 / (top - bottom), 0, 0},
+      TransformMatrix{{2 / width, 0, 0, 0},
+                      {0, 2 / height, 0, 0},
                       {0, 0, 2 / std::fabs(far_ - near_), 0},
                       {0, 0, 0, 1}} *
-      TransformMatrix{{1, 0, 0, -0.5 * (right - left)},
-                      {0, 1, 0, -0.5 * (top - bottom)},
+      TransformMatrix{{1, 0, 0, 0},
+                      {0, 1, 0, 0},
                       {0, 0, 1, -0.5 * (far_ - near_)},
                       {0, 0, 0, 1}};
   const TransformMatrix &inv_ortho_transform{
-      {(right - left) / 2., 0, 0, 0.5 * (right - left)},
-      {0, (top - bottom) / 2., 0, 0.5 * (top - bottom)},
+      {width / 2., 0, 0, 0},
+      {0, height / 2., 0, 0},
       {0, 0, std::fabs(far_ - near_) / 2., 0.5 * (far_ - near_)},
       {0, 0, 0, 1}};
 
@@ -184,7 +180,7 @@ cv::Mat MinusRenderer::render(const int resolution_width,
     auto primitives = (meshes_[mesh_index]).get_primitives();
     for (auto &t : primitives) {
       const auto [z_min, z_max] = t.get_depth_range();
-      if (z_max >= far_ && z_min <= near_) {
+      if (z_max >= far_ && z_min <= near_) { // because the camera looks at -z
         t.set_points(apply_transform(ss_transform, t.get_vertex_position()));
       }
     }
@@ -203,17 +199,13 @@ cv::Mat MinusRenderer::render(const int resolution_width,
       pixel_color = cv::Vec3b(0, 0, 0);
 
       const auto &fragment = shading_points[y][x];
-      if (fragment.triangle.mesh_index >= 0 &&
-          fragment.triangle.mesh_index < meshes_.size()) {
+      if (fragment.depth <= 1. && fragment.depth >= -1.) {
         const auto &mesh = meshes_[fragment.triangle.mesh_index];
-        if (fragment.depth <= 1. && fragment.depth >= -1.) {
-          const Point3d &position =
-              (inv_ss_transform *
-               (Point3d{x + 0.5, y + 0.5, fragment.depth}.homogeneous()))
-                  .hnormalized();
-
-          pixel_color = fragment_shader(fragment, position, mesh);
-        }
+        const Point3d &position =
+            (inv_ss_transform *
+             (Point3d{x + 0.5, y + 0.5, fragment.depth}.homogeneous()))
+                .hnormalized();
+        pixel_color = fragment_shader(fragment, position, mesh);
       }
     }
   }
diff --git a/src/phone_material.cc b/src/phone_material.cc
index 9447d22..91a8561 100644
--- a/src/phone_material.cc
+++ b/src/phone_material.cc
@@ -9,7 +9,7 @@
 PhoneMaterial::PhoneMaterial(
     const std::unordered_map<Texture::TextureType, std::shared_ptr<Texture>>
         &textures)
-    : textures_(textures), Ka(0.2), Ks(1.6),
+    : textures_(textures), Ka(0.1), Ks(1.2),
       specular_attenuation_factor_(defaultAttenuationFactor) {
   spdlog::info("Specular attenuation factor: {}", specular_attenuation_factor_);
 }
diff --git a/src/rasterizer.cc b/src/rasterizer.cc
index 618d245..661a5ee 100644
--- a/src/rasterizer.cc
+++ b/src/rasterizer.cc
@@ -19,8 +19,8 @@ void Rasterizer::rasterize(const int mesh_idx,
                            const std::vector<Triangle> &primitives) {
   const int thread_num = 8;
   std::vector<std::thread> rasterize_threads;
-  for (int begin = 0, offset = primitives.size() / thread_num,
-           remainer = (primitives.size() % thread_num);
+  for (size_t begin = 0, offset = primitives.size() / thread_num,
+              remainer = (primitives.size() % thread_num);
        begin < primitives.size();) {
     int end = begin + offset;
     if (remainer > 0) {
diff --git a/src/rasterizer.h b/src/rasterizer.h
index 2e89f92..b1466d7 100644
--- a/src/rasterizer.h
+++ b/src/rasterizer.h
@@ -10,8 +10,8 @@
 typedef struct RasterizerResult {
   double depth{-std::numeric_limits<double>::infinity()};
   struct {
-    int32_t mesh_index{-1};
-    int64_t triangle_index{-1};
+    size_t mesh_index;
+    size_t triangle_index;
   } triangle;
 } RasterizerResult;
 
diff --git a/src/util/math_util.h b/src/util/math_util.h
index f52b250..cc80bab 100644
--- a/src/util/math_util.h
+++ b/src/util/math_util.h
@@ -2,13 +2,6 @@
 // Author: tianlei.richard@qq.com (tianlei.richard)
 
 #include "common.h"
-#include <cmath>
-#include <numeric>
-
-template <typename FloatType>
-bool fequal(const FloatType a, const FloatType b) {
-  return std::fabs(a - b) <= std::numeric_limits<FloatType>::epsilon();
-}
 
 template <int d>
 std::vector<Eigen::Vector<double, d>>
@@ -16,8 +9,7 @@ apply_transform(const TransformMatrix &mtx,
                 const std::vector<Eigen::Vector<double, d>> &points) {
   std::vector<Eigen::Vector<double, d>> res{};
   for (const auto &p : points) {
-    const auto &transform_res = mtx * p.homogeneous();
-    res.push_back(transform_res.hnormalized());
+    res.push_back((mtx * p.homogeneous()).hnormalized());
   }
   return res;
 }
@@ -26,6 +18,6 @@ template <int d>
 void apply_transform_in_place(const TransformMatrix &mtx,
                               std::vector<Eigen::Vector<double, d>> &points) {
   for (auto &p : points) {
-    p = mtx * p.homogeneous().hnormalized();
+    p = (mtx * p.homogeneous()).hnormalized();
   }
 }