diff --git a/example02_threaded_raytracing/src/main.cpp b/example02_threaded_raytracing/src/main.cpp
index dfbded3..a5657b2 100644
--- a/example02_threaded_raytracing/src/main.cpp
+++ b/example02_threaded_raytracing/src/main.cpp
@@ -2,17 +2,27 @@
 #include <string>
 
 #include "argParse.hpp"
+#include "rayTracer.hpp"
 
 void printHelp() {
     std::cout << "Usage:\n"
         "-h | --help                Display this help message\n"
         "-t <integer>\n"
-        "   | --threads <integer>   Set the number of threads to use (default 1)"
+        "   | --threads <integer>   Set the number of threads to use (default 1)\n"
+        "--width <integer>          Set the width of the output image\n"
+        "--height <integer>         Set the height of the output image\n"
+        "--radius <float>           Set the radius of the sphere\n"
+        "-o <filename>\n"
+        "   | --output <filename>   Set the output filename for the image"
         << std::endl;
 }
 
 int main(int argc, char **argv) {
     int threadCount = 1;
+    unsigned int outputWidth = 1600;
+    unsigned int outputHeight = 1600;
+    float sphereRadius = 1.5f;
+    std::string outputFile = "raytrace_out";
 
     {
         auto results = Ex02::ArgParse::parseArgs(
@@ -25,6 +35,11 @@ int main(int argc, char **argv) {
             { // double args
                 "-t",
                 "--threads",
+                "--width",
+                "--height",
+                "--radius",
+                "-o",
+                "--output",
             });
 
         if(auto iter = results.find("-h"); iter != results.end()) {
@@ -58,7 +73,6 @@ int main(int argc, char **argv) {
                 return result;
             }
         }
-
         if(threadCount <= 0) {
             std::cout << "ERROR: Thread count set to invalid value ("
                 << threadCount
@@ -66,7 +80,73 @@ int main(int argc, char **argv) {
                 << std::endl;
             return 3;
         }
+        if(auto iter = results.find("--width"); iter != results.end()) {
+            try {
+                outputWidth = std::stoul(iter->second);
+            } catch (const std::invalid_argument &e) {
+                std::cout << "ERROR: Failed to parse width (invalid)"
+                    << std::endl;
+                return 3;
+            } catch (const std::out_of_range &e) {
+                std::cout << "ERROR: Failed to parse width (out of range)"
+                    << std::endl;
+                return 4;
+            }
+        }
+        if(outputWidth == 0) {
+            std::cout << "ERROR: width cannot be 0" << std::endl;
+            return 7;
+        }
+        if(auto iter = results.find("--height"); iter != results.end()) {
+            try {
+                outputHeight = std::stoul(iter->second);
+            } catch (const std::invalid_argument &e) {
+                std::cout << "ERROR: Failed to parse height (invalid)"
+                    << std::endl;
+                return 5;
+            } catch (const std::out_of_range &e) {
+                std::cout << "ERROR: Failed to parse height (out of range)"
+                    << std::endl;
+                return 6;
+            }
+        }
+        if(outputHeight == 0) {
+            std::cout << "ERROR: height cannot be 0" << std::endl;
+            return 8;
+        }
+        if(auto iter = results.find("--radius"); iter != results.end()) {
+            try {
+                sphereRadius = stof(iter->second);
+            } catch (const std::invalid_argument &e) {
+                std::cout << "ERROR: Failed to parse radius (invalid)"
+                    << std::endl;
+                return 9;
+            } catch (const std::out_of_range &e) {
+                std::cout << "ERROR: Failed to parse radius (out_of_range)"
+                    << std::endl;
+                return 10;
+            }
+        }
+        if(sphereRadius <= 0.0f) {
+            std::cout << "ERROR: radius must be positive and non-zero"
+                << std::endl;
+            return 11;
+        }
+        if(auto iter = results.find("-o"); iter != results.end()) {
+            outputFile = iter->second;
+        } else if(auto iter = results.find("--output"); iter != results.end()) {
+            outputFile = iter->second;
+        }
+        if(outputFile.empty()) {
+            std::cout << "ERROR: Output filename is empty" << std::endl;
+            return 12;
+        }
     }
 
+    auto pixels = Ex02::RT::renderGraySphere(
+        outputWidth, outputHeight, sphereRadius, threadCount);
+
+    Ex02::RT::writeGrayscaleToFile(pixels, outputWidth, outputFile);
+
     return 0;
 }
diff --git a/example02_threaded_raytracing/src/rayTracer.cpp b/example02_threaded_raytracing/src/rayTracer.cpp
index 7b847f9..eebef8c 100644
--- a/example02_threaded_raytracing/src/rayTracer.cpp
+++ b/example02_threaded_raytracing/src/rayTracer.cpp
@@ -1,6 +1,7 @@
 #include "rayTracer.hpp"
 
 #include <cmath>
+#include <fstream>
 
 #include <glm/matrix.hpp>
 #include <glm/gtc/matrix_transform.hpp>
@@ -15,7 +16,7 @@ glm::vec3 Ex02::RT::Internal::defaultSpherePos() {
 }
 
 glm::vec3 Ex02::RT::Internal::defaultLightPos() {
-    return glm::vec3{1.0f, 1.0f, 1.0f};
+    return glm::vec3{1.0f, 1.0f, 0.0f};
 }
 
 glm::mat4x4 Ex02::RT::Internal::defaultMVP() {
@@ -31,13 +32,65 @@ glm::mat4x4 Ex02::RT::Internal::defaultMVP() {
         glm::vec3{0.0f, 1.0f, 0.0f});
 
     // model pushes back by 2 units
-    mvp *= glm::translate(
-        glm::identity<glm::mat4x4>(),
-        glm::vec3{0.0f, 0.0f, -2.0f});
+    mvp = glm::translate(
+        mvp,
+        glm::vec3{0.0f, 0.0f, 2.0f});
 
     return mvp;
 }
 
+std::optional<glm::vec3> Ex02::RT::Internal::rayToSphere(
+        glm::vec3 rayPos,
+        glm::vec3 rayDir,
+        glm::vec3 spherePos,
+        float sphereRadius) {
+    // ensure rayDir is a unit vector
+    float rayDirLength = std::sqrt(
+            rayDir.x * rayDir.x
+            + rayDir.y * rayDir.y
+            + rayDir.z * rayDir.z);
+    rayDir /= rayDirLength;
+
+    // check if there is collision
+    glm::vec3 tempVec = rayPos - spherePos;
+    float temp =
+        rayDir.x * tempVec.x
+        + rayDir.y * tempVec.y
+        + rayDir.z * tempVec.z;
+    float delta = temp * temp;
+    temp =
+        tempVec.x * tempVec.x
+        + tempVec.y * tempVec.y
+        + tempVec.z * tempVec.z
+        - sphereRadius * sphereRadius;
+    delta -= temp;
+
+    if(delta < 0.0f) {
+        return {};
+    } else {
+        temp =
+            rayDir.x * tempVec.x
+            + rayDir.y * tempVec.y
+            + rayDir.z * tempVec.z;
+        float dist = -temp - std::sqrt(delta);
+        if(dist < 0.0f) {
+            dist = -temp + std::sqrt(delta);
+            if(dist < 0.0f) {
+                return {};
+            }
+        }
+        return {rayPos + rayDir * dist};
+    }
+}
+
+float Ex02::RT::Internal::angleBetweenRays(glm::vec3 a, glm::vec3 b) {
+    float dot = a.x * b.x + a.y * b.y + a.z * b.z;
+    float amag = std::sqrt(a.x * a.x + a.y * a.y + a.z * a.z);
+    float bmag = std::sqrt(b.x * b.x + b.y * b.y + b.z * b.z);
+
+    return std::acos(dot / amag / bmag);
+}
+
 std::vector<unsigned char> Ex02::RT::renderGraySphere(
         unsigned int outputWidth,
         unsigned int outputHeight,
@@ -47,6 +100,66 @@ std::vector<unsigned char> Ex02::RT::renderGraySphere(
         glm::vec3 lightPos,
         glm::mat4x4 mvp) {
     std::vector<unsigned char> grayscalePixels;
+    grayscalePixels.resize(outputWidth * outputHeight);
+
+//    glm::vec3 tr_spherePos = mvp * glm::vec4{spherePos, 1.0f};
+//    glm::vec3 tr_lightPos = mvp * glm::vec4{lightPos, 1.0f};
+    glm::vec3 tr_spherePos = glm::vec3{0.0f, 0.0f, -2.0f};
+    glm::vec3 tr_lightPos = glm::vec3{1.0f, 1.0f, 0.0f};
+    glm::vec3 rayPos{0.0f, 0.0f, 0.0f};
+    if(threadCount == 1) {
+        for(unsigned int j = 0; j < outputHeight; ++j) {
+            float offsetY = ((float)j - ((float)outputHeight / 2.0f));
+            for(unsigned int i = 0; i < outputWidth; ++i) {
+                float offsetX = ((float)i - ((float)outputWidth / 2.0f));
+                glm::vec3 rayDir = glm::vec3{
+                    offsetX, offsetY, -EX02_RAY_TRACER_DRAW_PLANE};
+                auto rayResult = Internal::rayToSphere(
+                        rayPos, rayDir, tr_spherePos, sphereRadius);
+                if(rayResult) {
+                    glm::vec3 toLight = *rayResult - tr_lightPos;
+                    toLight /= std::sqrt(
+                        toLight.x * toLight.x
+                        + toLight.y * toLight.y
+                        + toLight.z * toLight.z);
+                    glm::vec3 toLightPos = *rayResult + toLight * 2.4f;
+                    auto collResult = Internal::rayToSphere(
+                        toLightPos, toLight, tr_spherePos, sphereRadius);
+                    if(collResult) {
+                        continue;
+                    }
+
+                    glm::vec3 resultToLight = tr_lightPos - *rayResult;
+                    glm::vec3 resultToOrigin = rayPos - *rayResult;
+                    float angle = Internal::angleBetweenRays(
+                            resultToLight,
+                            resultToOrigin);
+                    if(angle <= PI && angle >= 0.0f) {
+                        grayscalePixels.at(i + j * outputWidth) =
+                            (1.0f - angle / PI) * 255.0f;
+                    }
+                }
+            }
+        }
+    } else {
+    }
 
     return grayscalePixels;
 }
+
+void Ex02::RT::writeGrayscaleToFile(
+        const std::vector<unsigned char> &pixels,
+        unsigned int outputWidth,
+        std::string filename) {
+    std::ofstream out(filename + ".pgm");
+    out << "P2\n" << outputWidth << ' ' << pixels.size() / outputWidth << " 255"
+        << '\n';
+
+    for(unsigned int j = 0; j < pixels.size() / outputWidth; ++j) {
+        for(unsigned int i = 0; i < outputWidth; ++i) {
+            out << (int)pixels.at(i + j * outputWidth)
+                << ' ';
+        }
+        out << '\n';
+    }
+}
diff --git a/example02_threaded_raytracing/src/rayTracer.hpp b/example02_threaded_raytracing/src/rayTracer.hpp
index 021752f..fef06b5 100644
--- a/example02_threaded_raytracing/src/rayTracer.hpp
+++ b/example02_threaded_raytracing/src/rayTracer.hpp
@@ -1,11 +1,14 @@
 #ifndef EX02_RAY_TRACER_HPP
 #define EX02_RAY_TRACER_HPP
 
+#define EX02_RAY_TRACER_DRAW_PLANE 500.0f
 #define EX02_RAY_TRACER_DEFAULT_NEAR_PLANE 0.2f
 #define EX02_RAY_TRACER_DEFAULT_FAR_PLANE 4.0f
 #define EX02_RAY_TRACER_COLL_INCREMENT 2.0f
 
 #include <vector>
+#include <optional>
+#include <string>
 
 #include <glm/vec3.hpp>
 #include <glm/mat4x4.hpp>
@@ -18,6 +21,16 @@ namespace Internal {
     glm::vec3 defaultSpherePos();
     glm::vec3 defaultLightPos();
     glm::mat4x4 defaultMVP();
+
+    std::optional<glm::vec3> rayToSphere(
+        glm::vec3 rayPos,
+        glm::vec3 rayDir,
+        glm::vec3 spherePos,
+        float sphereRadius);
+
+    float angleBetweenRays(
+        glm::vec3 a,
+        glm::vec3 b);
 }
 
 std::vector<unsigned char> renderGraySphere(
@@ -30,6 +43,11 @@ std::vector<unsigned char> renderGraySphere(
     glm::mat4x4 mvp = Internal::defaultMVP()
 );
 
+void writeGrayscaleToFile(
+    const std::vector<unsigned char> &pixels,
+    unsigned int outputWidth,
+    std::string filename);
+
 } // namespace RT
 } // namespace Ex02