feat: add model matrix transformation hierarchy and delta time tracking

initializes the full graphics context pipeline required for modern OpenGL rendering

.gitignore

@@ -1,3 +1,4 @@
 cmake-build-debug
 SDL
 .idea/
+external/

CMakeLists.txt

@@ -8,10 +8,26 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/$<CONFIGURATION>")
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/$<CONFIGURATION>")
 
 # This assumes the SDL source is available in SDL
-add_subdirectory(SDL EXCLUDE_FROM_ALL)
+add_subdirectory(external/SDL EXCLUDE_FROM_ALL)
+add_subdirectory(external/cglm EXCLUDE_FROM_ALL)
+#add_subdirectory(glad EXCLUDE_FROM_ALL)
 
 # Create your game executable target as usual
-add_executable(BeyondDepth WIN32 main.c)
+add_executable(BeyondDepth src/main.c
+        src/engine/core/logger/log.c
+        src/engine/renderer/camera/camera.c
+        src/engine/renderer/camera/camera.h
+        external/glad/src/glad.c
+        src/engine/renderer/shaders/shader.c
+        src/engine/renderer/shaders/shader.h
+        src/engine/renderer/data/engine_data.h
+        src/engine/renderer/mesh/mesh.c
+        src/engine/renderer/mesh/mesh.h)
 
-# Link to the actual SDL3 library.
+set_target_properties(BeyondDepth PROPERTIES WIN32_EXECUTABLE FALSE)
-target_link_libraries(BeyondDepth PRIVATE SDL3::SDL3)
+
+target_include_directories(BeyondDepth PRIVATE external/glad/include)
+
+target_link_libraries(BeyondDepth PRIVATE
+        SDL3::SDL3
+        cglm)

main.c

@@ -1,67 +0,0 @@
-/*
-  Copyright (C) 1997-2025 Sam Lantinga <slouken@libsdl.org>
-
-  This software is provided 'as-is', without any express or implied
-  warranty.  In no event will the authors be held liable for any damages
-  arising from the use of this software.
-
-  Permission is granted to anyone to use this software for any purpose,
-  including commercial applications, and to alter it and redistribute it
-  freely.
-*/
-#define SDL_MAIN_USE_CALLBACKS 1  /* use the callbacks instead of main() */
-#include <SDL3/SDL.h>
-#include <SDL3/SDL_main.h>
-
-static SDL_Window *window = NULL;
-static SDL_Renderer *renderer = NULL;
-
-/* This function runs once at startup. */
-SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
-{
-    /* Create the window */
-    if (!SDL_CreateWindowAndRenderer("Hello World", 800, 600, SDL_WINDOW_FULLSCREEN, &window, &renderer)) {
-        SDL_Log("Couldn't create window and renderer: %s", SDL_GetError());
-        return SDL_APP_FAILURE;
-    }
-    return SDL_APP_CONTINUE;
-}
-
-/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
-SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
-{
-    if (event->type == SDL_EVENT_KEY_DOWN ||
-        event->type == SDL_EVENT_QUIT) {
-        return SDL_APP_SUCCESS;  /* end the program, reporting success to the OS. */
-    }
-    return SDL_APP_CONTINUE;
-}
-
-/* This function runs once per frame, and is the heart of the program. */
-SDL_AppResult SDL_AppIterate(void *appstate)
-{
-    const char *message = "Hello World!";
-    int w = 0, h = 0;
-    float x, y;
-    const float scale = 4.0f;
-
-    /* Center the message and scale it up */
-    SDL_GetRenderOutputSize(renderer, &w, &h);
-    SDL_SetRenderScale(renderer, scale, scale);
-    x = ((w / scale) - SDL_DEBUG_TEXT_FONT_CHARACTER_SIZE * SDL_strlen(message)) / 2;
-    y = ((h / scale) - SDL_DEBUG_TEXT_FONT_CHARACTER_SIZE) / 2;
-
-    /* Draw the message */
-    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
-    SDL_RenderClear(renderer);
-    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
-    SDL_RenderDebugText(renderer, x, y, message);
-    SDL_RenderPresent(renderer);
-
-    return SDL_APP_CONTINUE;
-}
-
-/* This function runs once at shutdown. */
-void SDL_AppQuit(void *appstate, SDL_AppResult result)
-{
-}

src/engine/core/logger/log.c

@@ -0,0 +1,168 @@
+/*
+ * Copyright (c) 2020 rxi
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "log.h"
+
+#define MAX_CALLBACKS 32
+
+typedef struct {
+  log_LogFn fn;
+  void *udata;
+  int level;
+} Callback;
+
+static struct {
+  void *udata;
+  log_LockFn lock;
+  int level;
+  bool quiet;
+  Callback callbacks[MAX_CALLBACKS];
+} L;
+
+
+static const char *level_strings[] = {
+  "TRACE", "DEBUG", "INFO", "WARN", "ERROR", "FATAL"
+};
+
+#ifdef LOG_USE_COLOR
+static const char *level_colors[] = {
+  "\x1b[94m", "\x1b[36m", "\x1b[32m", "\x1b[33m", "\x1b[31m", "\x1b[35m"
+};
+#endif
+
+
+static void stdout_callback(log_Event *ev) {
+  char buf[16];
+  buf[strftime(buf, sizeof(buf), "%H:%M:%S", ev->time)] = '\0';
+#ifdef LOG_USE_COLOR
+  fprintf(
+    ev->udata, "%s %s%-5s\x1b[0m \x1b[90m%s:%d:\x1b[0m ",
+    buf, level_colors[ev->level], level_strings[ev->level],
+    ev->file, ev->line);
+#else
+  fprintf(
+    ev->udata, "%s %-5s %s:%d: ",
+    buf, level_strings[ev->level], ev->file, ev->line);
+#endif
+  vfprintf(ev->udata, ev->fmt, ev->ap);
+  fprintf(ev->udata, "\n");
+  fflush(ev->udata);
+}
+
+
+static void file_callback(log_Event *ev) {
+  char buf[64];
+  buf[strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", ev->time)] = '\0';
+  fprintf(
+    ev->udata, "%s %-5s %s:%d: ",
+    buf, level_strings[ev->level], ev->file, ev->line);
+  vfprintf(ev->udata, ev->fmt, ev->ap);
+  fprintf(ev->udata, "\n");
+  fflush(ev->udata);
+}
+
+
+static void lock(void)   {
+  if (L.lock) { L.lock(true, L.udata); }
+}
+
+
+static void unlock(void) {
+  if (L.lock) { L.lock(false, L.udata); }
+}
+
+
+const char* log_level_string(int level) {
+  return level_strings[level];
+}
+
+
+void log_set_lock(log_LockFn fn, void *udata) {
+  L.lock = fn;
+  L.udata = udata;
+}
+
+
+void log_set_level(int level) {
+  L.level = level;
+}
+
+
+void log_set_quiet(bool enable) {
+  L.quiet = enable;
+}
+
+
+int log_add_callback(log_LogFn fn, void *udata, int level) {
+  for (int i = 0; i < MAX_CALLBACKS; i++) {
+    if (!L.callbacks[i].fn) {
+      L.callbacks[i] = (Callback) { fn, udata, level };
+      return 0;
+    }
+  }
+  return -1;
+}
+
+
+int log_add_fp(FILE *fp, int level) {
+  return log_add_callback(file_callback, fp, level);
+}
+
+
+static void init_event(log_Event *ev, void *udata) {
+  if (!ev->time) {
+    time_t t = time(NULL);
+    ev->time = localtime(&t);
+  }
+  ev->udata = udata;
+}
+
+
+void log_log(int level, const char *file, int line, const char *fmt, ...) {
+  log_Event ev = {
+    .fmt   = fmt,
+    .file  = file,
+    .line  = line,
+    .level = level,
+  };
+
+  lock();
+
+  if (!L.quiet && level >= L.level) {
+    init_event(&ev, stderr);
+    va_start(ev.ap, fmt);
+    stdout_callback(&ev);
+    va_end(ev.ap);
+  }
+
+  for (int i = 0; i < MAX_CALLBACKS && L.callbacks[i].fn; i++) {
+    Callback *cb = &L.callbacks[i];
+    if (level >= cb->level) {
+      init_event(&ev, cb->udata);
+      va_start(ev.ap, fmt);
+      cb->fn(&ev);
+      va_end(ev.ap);
+    }
+  }
+
+  unlock();
+}

src/engine/core/logger/log.h

@@ -0,0 +1,49 @@
+/**
+ * Copyright (c) 2020 rxi
+ *
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the MIT license. See `log.c` for details.
+ */
+
+#ifndef LOG_H
+#define LOG_H
+
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <time.h>
+
+#define LOG_VERSION "0.1.0"
+
+typedef struct {
+  va_list ap;
+  const char *fmt;
+  const char *file;
+  struct tm *time;
+  void *udata;
+  int line;
+  int level;
+} log_Event;
+
+typedef void (*log_LogFn)(log_Event *ev);
+typedef void (*log_LockFn)(bool lock, void *udata);
+
+enum { LOG_TRACE, LOG_DEBUG, LOG_INFO, LOG_WARN, LOG_ERROR, LOG_FATAL };
+
+#define log_trace(...) log_log(LOG_TRACE, __FILE__, __LINE__, __VA_ARGS__)
+#define log_debug(...) log_log(LOG_DEBUG, __FILE__, __LINE__, __VA_ARGS__)
+#define log_info(...)  log_log(LOG_INFO,  __FILE__, __LINE__, __VA_ARGS__)
+#define log_warn(...)  log_log(LOG_WARN,  __FILE__, __LINE__, __VA_ARGS__)
+#define log_error(...) log_log(LOG_ERROR, __FILE__, __LINE__, __VA_ARGS__)
+#define log_fatal(...) log_log(LOG_FATAL, __FILE__, __LINE__, __VA_ARGS__)
+
+const char* log_level_string(int level);
+void log_set_lock(log_LockFn fn, void *udata);
+void log_set_level(int level);
+void log_set_quiet(bool enable);
+int log_add_callback(log_LogFn fn, void *udata, int level);
+int log_add_fp(FILE *fp, int level);
+
+void log_log(int level, const char *file, int line, const char *fmt, ...);
+
+#endif

src/engine/renderer/camera/camera.c

@@ -0,0 +1,127 @@
+//
+// Created by Tristan on 10/16/2025.
+//
+
+#include "camera.h"
+#include "../..//core/logger/log.h"
+#include <cglm/cglm.h>
+#include "../shaders/shader.h"
+
+void camera_init(Camera *self, vec3 initial_position, int width, int height) {
+    // copy initial_pos vector
+    glm_vec3_copy(initial_position, self->Position);
+
+    // initialize orientation vector
+    glm_vec3_copy((vec3){0.0f, 0.0f, -1.0f}, self->Orientation);
+
+    // initialize up vector
+    glm_vec3_copy((vec3){0.0f, 1.0f, 0.0f}, self->Up);
+
+    // initialize controls and viewport
+    self->speed = 0.9f;
+    self->sensitivity = 3.5f;
+    self->FOV_deg = 45.0f;
+    self->yaw = -90.0f;
+    self->pitch = 0.0f;
+
+    self->width = width;
+    self->height = height;
+
+    // Init view matrix to identity (for first frame)
+    glm_mat4_identity(self->View);
+}
+
+void camera_update_view_matrix(Camera *self) {
+    // calc the center or target point (Pos + Orientation)
+    vec3 target;
+    glm_vec3_add(self->Position, self->Orientation, target);
+
+    // create view matrix
+    glm_lookat(self->Position, target, self->Up, self->View);
+}
+
+void camera_update_projection(Camera *self, float nearPlane, float farPlane, mat4 dest) {
+    float aspect = (float)self->width / (float)self->height;
+    glm_perspective(glm_rad(self->FOV_deg), aspect, nearPlane, farPlane, dest);
+}
+
+// TODO: Update matrix function signature to accept camera entity?
+// change name to camera_upload_matrix for clarity?
+void camera_matrix_to_shader(Camera *self, Shader *shader, const char *uniform_name) {
+    // update the view matrix first, camera position might have moved
+    camera_update_view_matrix(self);
+
+    // calculate projection matrix (P) with temporary matrix 'projection' for the result
+    mat4 projection;
+    camera_update_projection(self, 0.001f, 100.0f, projection);
+
+    // combine the matrices -- P * V -> PV
+    mat4 view_projection;
+    glm_mat4_mul(projection, self->View, view_projection);
+
+    // get uniform location
+    GLint uniform_location = shader->camMatrixLocation;
+
+    if (uniform_location == -1) {
+        // log_error("Warning: Uniform '%s' not found in shader program %u.\n", uniform_name, shader);
+        return;
+    }
+
+    // upload combined matrix to the shader
+    // view_projection[0] array pointer decays to first value
+    glUniformMatrix4fv(uniform_location, 1, GL_FALSE, *view_projection);
+}
+
+void camera_process_keyboard(Camera *self, const Uint8 *keyState, float deltaTime) {
+    vec3 move;
+    float current_speed = self->speed * deltaTime;
+
+    // forward/back
+    if (keyState[SDL_SCANCODE_W]) {
+        glm_vec3_scale(self->Orientation, current_speed, move);
+        glm_vec3_add(self->Position, move, self->Position);
+    }
+
+    if (keyState[SDL_SCANCODE_S]) {
+        glm_vec3_scale(self->Orientation, current_speed, move);
+        glm_vec3_sub(self->Position, move, self->Position);
+    }
+
+    // strafe left/right
+    vec3 right;
+    glm_vec3_cross(self->Orientation, self->Up, right);
+    glm_vec3_normalize(right);
+
+    if (keyState[SDL_SCANCODE_A]) {
+        glm_vec3_scale(right, current_speed, move);
+        glm_vec3_sub(self->Position, move, self->Position);
+    }
+
+    if (keyState[SDL_SCANCODE_D]) {
+        glm_vec3_scale(right, current_speed, move);
+        glm_vec3_add(self->Position, move, self->Position);
+    }
+}
+
+// TODO: add deltaTime arg for smoother rotation
+void camera_process_mouse(Camera *self, float xoffset, float yoffset, float deltaTime) {
+    float effective_sensitivity = self->sensitivity * deltaTime;
+    xoffset *= effective_sensitivity;
+    yoffset *= effective_sensitivity;
+
+    self->yaw += xoffset;
+    self->pitch += yoffset;
+
+    // clamps the pitch to prevent camera from flipping upside down
+    if (self->pitch > 89.0f)
+        self->pitch = 89.0f;
+    if (self->pitch < -89.0f)
+        self->pitch = -89.0f;
+
+    // calc new orientation vector from yaw and pitch
+    vec3 new_orientation;
+    new_orientation[0] = cos(glm_rad(self->yaw)) * cos(glm_rad(self->pitch));
+    new_orientation[1] = sin(glm_rad(self->pitch));
+    new_orientation[2] = sin(glm_rad(self->yaw)) * cos(glm_rad(self->pitch));
+    glm_vec3_normalize_to(new_orientation, self->Orientation);
+}

src/engine/renderer/camera/camera.h

@@ -0,0 +1,45 @@
+//
+// Created by Tristan on 10/16/2025.
+//
+
+#ifndef CAMERA_H
+#define CAMERA_H
+
+#include <SDL3/SDL.h>
+#include <cglm/cglm.h>
+#include "../shaders/shader.h"
+
+typedef struct {
+    vec3 Position;
+    vec3 Orientation;
+    vec3 Up;
+    float yaw;
+    float pitch;
+    float speed;
+    float sensitivity;
+    float FOV_deg;
+    int width;
+    int height;
+    mat4 View; // cache for the calculated View Matrix
+} Camera;
+
+// initializer
+void camera_init(Camera *self, vec3 initial_position, int width, int height);
+
+/* --- Matrix calculation functions --- */
+// Updates self->View matrix based on pos, orientation and up
+void camera_update_view_matrix(Camera *self);
+
+// calculates the projection matrix for a given set of planes
+void camera_update_projection(Camera *self, float nearPlane, float forPlane, mat4 dest);
+
+// generates (projection * view) and uploads to the shader program
+void camera_matrix_to_shader(Camera *self, Shader *shader, const char *uniform_name);
+
+// TODO: Input handling (needs full SDL context later)
+void camera_inputs(Camera *self, SDL_Event *event);
+
+void camera_process_keyboard(Camera *self, const Uint8 *keystate, float deltaTime);
+void camera_process_mouse(Camera *self, float xoffset, float yoffset, float deltaTime);
+
+#endif //CAMERA_H

src/engine/renderer/data/engine_data.h

@@ -0,0 +1,33 @@
+//
+// Created by Tristan on 10/17/2025.
+//
+
+#ifndef ENGINE_DATA_H
+#define ENGINE_DATA_H
+
+#include <SDL3/SDL.h>
+#include "../camera/camera.h"
+#include "../mesh/mesh.h"
+
+typedef struct {
+    // Camera instance
+    Camera camera;
+
+    // Shader program instance
+    Shader shader;
+
+    // Mesh instance
+    Mesh triangle_mesh;
+    mat4 pyramidModel;
+
+    // Keep track of window size
+    int window_width;
+    int window_height;
+
+    float lastFrameTime; // time of the previous frame
+    float deltaTime; // time elapsed since the last frame
+
+    // TODO: Add other components, SDL_Window* or Meshes, etc...
+} Engine_Data;
+
+#endif //ENGINE_DATA_H

src/engine/renderer/mesh/mesh.c

@@ -0,0 +1,93 @@
+//
+// Created by Tristan on 10/17/2025.
+//
+
+#include "mesh.h"
+#include "../../core/logger/log.h"
+#include <stdlib.h>
+
+GLfloat vertices[] = {
+    // Position         // Color
+    // X     Y     Z     R     G     B    // Index
+    -0.5f, -0.5f,  0.0f, 1.0f, 0.0f, 0.0f, // 0: Apex
+     0.5f, -0.5f,  0.0f, 0.0f, 1.0f, 0.0f, // 1: Base Corner 1 (Red)
+     0.0f,  0.5f,  0.0f, 0.0f, 0.0f, 1.0f, // 2: Base Corner 2 (Green)
+     0.0f, -0.5f, -0.5f, 0.0f, 0.0f, 1.0f  // 3: Base Corner 3 (Blue)
+};
+
+const size_t vertices_size = sizeof(vertices);
+
+GLuint indices[] = {
+    // side 1: (Apex, C1, C2)
+    0, 1, 2, // vertices that form the triangle
+
+    // side2: (Apex, C2, C3)
+    0, 2, 3,
+
+    // side 3: (Apex, C3, C1)
+    0, 3, 1,
+
+    // base: (C1, C3, C2) - order is crucial for culling
+    1, 3, 2
+
+};
+
+void mesh_init(Mesh *self, GLfloat *vertices, GLsizei vertices_size, GLuint *indices, GLsizei num_indices) {
+    self->num_indices = num_indices;
+
+    // generate buffers, vao, vbo, ebo
+    glGenVertexArrays(1, &self->VAO);
+    glGenBuffers(1, &self->VBO);
+    glGenBuffers(1, &self->EBO);
+
+    // bind the VAO
+    glBindVertexArray(self->VAO);
+
+    // bind and upload VBO data
+    glBindBuffer(GL_ARRAY_BUFFER, self->VBO);
+    glBufferData(GL_ARRAY_BUFFER, vertices_size, vertices, GL_STATIC_DRAW);
+
+    // bind and upload ebo data
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, self->EBO);
+    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLuint) * num_indices, indices, GL_STATIC_DRAW);
+
+    // configure vertex attributes
+    // a. Position attribute (layout = 0)
+    // 3 floats per pos, stride = 6 floats total (3 pos + 3 colour), offset is 0
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (void*)0);
+    glEnableVertexAttribArray(0);
+
+    // b. Color attribute (layout = 1)
+    // 3 floats per color, stride = 6 floats total, offset is 3 floats (after pos)
+    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat)));
+    glEnableVertexAttribArray(1);
+
+    // TODO: hader also expects layout = 2 but lazy, pray no crash
+
+    // unbind the VAO (so it can't be modified)
+    glBindVertexArray(0);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+
+    log_info("Mesh initialized with VAO: %u", self->VAO);
+}
+
+void mesh_draw(Mesh *self) {
+    // bind the vao
+    glBindVertexArray(self->VAO);
+
+    // draw the triangle
+    glDrawElements(GL_TRIANGLES, self->num_indices, GL_UNSIGNED_INT, 0);
+
+    // unbind
+    glBindVertexArray(0);
+}
+
+void mesh_delete(Mesh *self) {
+    glDeleteVertexArrays(1, &self->VAO);
+    glDeleteBuffers(1, &self->VBO);
+    glDeleteBuffers(1, &self->EBO);
+    self->VAO = 0;
+    self->VBO = 0;
+    self->EBO = 0;
+}

src/engine/renderer/mesh/mesh.h

@@ -0,0 +1,43 @@
+//
+// Created by Tristan on 10/17/2025.
+//
+
+#ifndef MESH_H
+#define MESH_H
+
+#include <glad/glad.h>
+#include <cglm/cglm.h>
+
+// Vertices for a simple 2D triangle (x, y, z)
+// Add (r, g, b) color data after each pos
+// X, Y, Z, R, G, B
+extern GLfloat vertices[];
+extern const size_t vertices_size;
+// Indices define the order vertices are drawn
+extern GLuint indices[];
+
+#define INDICES_COUNT 12
+
+typedef struct {
+    // Vertex Array Object
+    GLuint VAO;
+
+    // Vertex Buffer Object
+    GLuint VBO;
+
+    // Element Buffer Object
+    GLuint EBO;
+
+    // Number of indices to draw
+    GLsizei num_indices;
+} Mesh;
+
+// initializes and uploads mesh data to gpu
+void mesh_init(Mesh *self, GLfloat *vertices, GLsizei vertices_size, GLuint *indices, GLsizei num_indices);
+
+// Draws the mesh
+void mesh_draw(Mesh *self);
+
+void mesh_delete(Mesh *self);
+
+#endif //MESH_H

src/engine/renderer/shaders/default.frag

@@ -0,0 +1,18 @@
+#version 330 core
+
+// Outputs colors in RGBA
+out vec4 FragColor;
+
+// Inputs the color from the vertex shader
+in vec3 color;
+
+// Inputs the texture coordinates from the vertex shader
+in vec2 texCoord;
+
+// get the texture unit from the main function
+uniform sampler2D tex0;
+
+void main()
+{
+    FragColor = texture(tex0, texCoord);
+}

src/engine/renderer/shaders/default.vert

@@ -0,0 +1,22 @@
+#version 330 core
+layout (location = 0) in vec3 aPos; // Vertex Position
+layout (location = 1) in vec3 aColor; // Vertex Color
+layout (location = 2) in vec2 aTex; // Texture coordinates
+
+// Outputs the color for the Fragment shader
+out vec3 color;
+// Outputs the texture coordinates for the Fragment shader
+out vec2 texCoord;
+
+// Imports the camera matrix from the main function
+uniform mat4 camMatrix;
+
+void main()
+{
+    // Apply the combined P*V matrix to transform the vertex position.
+    gl_Position = camMatrix * vec4(aPos, 1.0);
+    // Assigns the colors from the Vertex Data to "color"
+    color = aColor;
+    // Assigns the texture coordinates from the Vertex Data to "texCoord"
+    texCoord = aTex;
+}

src/engine/renderer/shaders/shader.c

@@ -0,0 +1,129 @@
+//
+// Created by Tristan on 10/16/2025.
+//
+
+#include "shader.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include "../../core/logger/log.h"
+
+// reads entire file contents into a string
+char *get_file_contents(const char *filename) {
+    FILE *fp;
+    long length;
+    char *buffer = NULL;
+
+    fp = fopen(filename, "rb");
+    if (!fp) {
+        log_error("Could not open file '%s'. Reason: %s\n", filename, strerror(errno));
+        return NULL;
+    }
+
+    fseek(fp, 0, SEEK_END);
+    length = ftell(fp);
+    fseek(fp, 0, SEEK_SET);
+
+    buffer = (char *)malloc(length + 1);
+    if (!buffer) {
+        log_error("Memory allocation failed for file '%s'.\n", filename);
+        fclose(fp);
+        return NULL;
+    }
+
+    fread(buffer, 1, length, fp);
+    buffer[length] = '\0';
+    fclose(fp);
+    return buffer;
+}
+
+// check if the different shaders have compiled properly
+void compile_errors(unsigned int shader, const char *type) {
+    GLint hasCompiled;
+    char infoLog[1024];
+
+    if (strcmp(type, "PROGRAM") != 0) {
+        glGetShaderiv(shader, GL_COMPILE_STATUS, &hasCompiled);
+        if (hasCompiled == GL_FALSE) {
+            glGetShaderInfoLog(shader, 1024, NULL, infoLog);
+            log_error("SHADER_COMPILATION_ERROR for: %s\n%s", type, infoLog);
+        }
+    } else {
+        glGetProgramiv(shader, GL_LINK_STATUS, &hasCompiled);
+        if (hasCompiled == GL_FALSE) {
+            glGetShaderInfoLog(shader, 1024, NULL, infoLog);
+            log_error("SHADER_LINKING_ERROR for %s\n%s", type, infoLog);
+        }
+    }
+}
+
+// build the shader program from 2 different shaders
+Shader shader_create(const char *vertexFile, const char *fragmentFile) {
+    // read shader source files
+    char *vertexSource = get_file_contents(vertexFile);
+    char *fragmentSource = get_file_contents(fragmentFile);
+
+    if (vertexSource == NULL || fragmentSource == NULL) {
+        log_error("Failed to load shader files. Returning empty shader\n");
+        Shader emptyShader = { .ID = 0, .camMatrixLocation = -1};
+        if (vertexSource)
+            free(vertexSource);
+        if (fragmentSource)
+            free(fragmentSource);
+        return emptyShader;
+    }
+
+    // compile vertex shader
+    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
+    glShaderSource(vertexShader, 1, (const char *const *)&vertexSource, NULL);
+    glCompileShader(vertexShader);
+    compile_errors(vertexShader, "VERTEX");
+
+    // compile fragment shader
+    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
+    glShaderSource(fragmentShader, 1, (const char *const *)&fragmentSource, NULL);
+    glCompileShader(fragmentShader);
+    compile_errors(fragmentShader, "FRAGMENT");
+
+    // cleanup strings after compilation
+    free(vertexSource);
+    free(fragmentSource);
+
+    // link shaders into a program
+    GLuint programID = glCreateProgram();
+    glAttachShader(programID, vertexShader);
+    glAttachShader(programID, fragmentShader);
+    glLinkProgram(programID);
+    compile_errors(programID, "PROGRAM");
+
+    // cleanup temporary shaders now that we've linked into the program
+    glDeleteShader(vertexShader);
+    glDeleteShader(fragmentShader);
+
+    GLint camMatrixLocation = glGetUniformLocation(programID, "camMatrix");
+    if (camMatrixLocation == -1) {
+        log_error("Uniform 'camMatrix' not found after linking shader program %u. Is it used in default.vert?", programID);
+    }
+
+    GLint modelMatrixLocation = glGetUniformLocation(programID, "modelMatrix");
+    if (modelMatrixLocation == -1) {
+        log_warn("Uniform 'modelMatrix' not found in shader program %u. Is it used in default.vert?", programID);
+    }
+
+    Shader newShader = {    .ID = programID,
+                            .camMatrixLocation = camMatrixLocation,
+                            .modelMatrixLocation = modelMatrixLocation };
+    return newShader;
+}
+
+// activates the shader program
+void shader_activate(Shader *self) {
+    glUseProgram(self->ID);
+}
+
+// deletes the shader program
+void shader_delete(Shader *self) {
+    glDeleteProgram(self->ID);
+    self->ID = 0; // just in-case
+}

src/engine/renderer/shaders/shader.h

@@ -0,0 +1,31 @@
+//
+// Created by Tristan on 10/16/2025.
+//
+
+#ifndef SHADER_H
+#define SHADER_H
+
+#include <glad/glad.h>
+#include <string.h>
+
+typedef struct {
+    // Reference ID of the shader program
+    GLuint ID;
+    // Location of the camera matrix uniform, set at creation
+    GLint camMatrixLocation;
+    GLint modelMatrixLocation;
+} Shader;
+
+char *get_file_contents(const char *filename);
+
+Shader shader_create(const char *vertexFile, const char *fragmentFile);
+
+// Takes a pointer to the instance
+void shader_activate(Shader *self);
+void shader_delete(Shader *self);
+
+// Private helper on shaderClass.h C++ header -- no private in C :)
+void compile_errors(unsigned int shader, const char *type);
+
+
+#endif //SHADER_H

src/main.c

@@ -0,0 +1,213 @@
+/*
+  Copyright (C) 1997-2025 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely.
+*/
+#define SDL_MAIN_USE_CALLBACKS 1  /* use the callbacks instead of main() */
+#include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
+#include <cglm/cglm.h>
+#include "engine/core/logger/log.h"
+#include "engine/renderer/camera/camera.h"
+#include "engine/renderer/data/engine_data.h"
+#include "engine/renderer/shaders/shader.h"
+#include "engine/renderer/mesh/mesh.h"
+
+static SDL_Window *window = NULL;
+static SDL_GLContext gl_context = NULL;
+
+/* This function runs once at startup. */
+SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
+{
+    //log_set_level(2);
+    log_info("Starting program and initializing SDL...");
+    /* Create the window */
+
+    int win_width = 1280;
+    int win_height = 720;
+
+    // TODO: make use of arena allocators potentially? see: digital grove repo
+    Engine_Data *state = (Engine_Data*)malloc(sizeof(Engine_Data));
+    if (state == NULL) {
+        log_error("Failed to allocate engine_data state, %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+
+    state->window_width = win_width;
+    state->window_height = win_height;
+
+    // create openGL context with openGL 3.3 core profile
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
+
+    // use of SDL_WINDOW_OPENGL flag to create a context-compatible window with shaders
+    window = SDL_CreateWindow("Beyond Depth", win_width, win_height, SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);
+    if (!window) {
+        log_error("Couldn't create SDL window: %s", SDL_GetError());
+        free(state);
+        return SDL_APP_FAILURE;
+    }
+
+    gl_context = SDL_GL_CreateContext(window);
+    if (!gl_context) {
+        log_error("Failed to create OpenGL context: %s", SDL_GetError());
+        SDL_DestroyWindow(window);
+        free(state);
+        return SDL_APP_FAILURE;
+    }
+
+    // initialize GLAD
+    // loads all the OpenGL function pointers
+    if (!gladLoadGLLoader((GLADloadproc)SDL_GL_GetProcAddress)) {
+        log_error("Failed to initialize GLAD");
+        SDL_GL_DestroyContext(gl_context);
+        SDL_DestroyWindow(window);
+        free(state);
+        return SDL_APP_FAILURE;
+    }
+
+    // z-buffer
+    glEnable(GL_DEPTH_TEST);
+
+    state->shader = shader_create("default.vert", "default.frag");
+    if (state->shader.ID == 0) {
+        log_error("Failed to initialize shader program");
+        // TODO: cleanup memory
+        return SDL_APP_FAILURE;
+    }
+
+    vec3 initial_pos = {0.0f, 0.0f, 2.0f};
+    camera_init(&state->camera, initial_pos, state->window_width, state->window_height);
+
+    mesh_init(&state->triangle_mesh, vertices, (GLsizei)vertices_size, indices, INDICES_COUNT);
+
+    glm_mat4_identity(state->pyramidModel);
+
+    SDL_SetWindowRelativeMouseMode(window, true);
+
+    // pass allocated state back to the SDL loop
+    *appstate = state;
+
+    log_info("Camera, Shaders and App State initialized");
+
+    return SDL_APP_CONTINUE;
+}
+
+/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
+SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
+{
+    Engine_Data *state = (Engine_Data *)appstate;
+
+    // handles quitting
+    if (event->type == SDL_EVENT_QUIT) {
+        return SDL_APP_SUCCESS;
+    }
+
+    // handles esc key to quit
+    if (event->type == SDL_EVENT_KEY_DOWN && event->key.key == SDLK_ESCAPE) {
+        return SDL_APP_SUCCESS;
+    }
+
+    // handle mouse motion for camera look
+    if (event->type == SDL_EVENT_MOUSE_MOTION) {
+        // y movement inverted?
+        camera_process_mouse(&state->camera, event->motion.xrel, -event->motion.yrel, state->deltaTime);
+    }
+
+    return SDL_APP_CONTINUE;
+}
+
+
+/* This function runs once per frame, and is the heart of the program. */
+SDL_AppResult SDL_AppIterate(void *appstate)
+{
+    Engine_Data *state = (Engine_Data *)appstate; // good practice
+
+    float currentTime = (float)SDL_GetTicks() / 1000.0f;
+    state->deltaTime = currentTime - state->lastFrameTime;
+    state->lastFrameTime = currentTime;
+
+    const Uint8 *keyState = SDL_GetKeyboardState(NULL);
+    camera_process_keyboard(&state->camera, keyState, state->deltaTime);
+
+    // set viewport
+    glViewport(0, 0, 1280, 720);
+
+    // clear the screen before drawing
+    // TODO: macros for colours so its easier to read? 0.07f does nothing for me context wise lol
+    glClearColor(0.07f, 0.13f, 0.17f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+    // calculate "orbit" angle for total rotation overtime
+    float rotation_speed_deg = 45.0f;
+    float rotation_amount = glm_rad(rotation_speed_deg * state->deltaTime);
+
+    // accumulate total rotation
+    static float total_rotation = 0.0f;
+    total_rotation += rotation_amount;
+
+    shader_activate(&state->shader);
+
+    // upload camera matrix (P*V) to the shader
+    camera_matrix_to_shader(&state->camera, &state->shader, "camMatrix");
+
+    float rotation = (float)SDL_GetTicks() / 1000.0f;
+    glm_mat4_identity(state->pyramidModel);
+    // rotate around the y-axis
+    glm_rotate(state->pyramidModel, total_rotation * 0.5f, (vec3){0.0f, 1.0f, 0.0f});
+
+    mat4 orbitModel; // temporary object
+    glm_mat4_identity(orbitModel);
+
+    glm_rotate(orbitModel, total_rotation, (vec3){0.0f, 1.0f, 0.0f});
+
+    glm_translate(orbitModel, (vec3){3.0f, 0.0f, 0.0f});
+
+    glm_rotate(orbitModel, total_rotation * 2.0f, (vec3){0.5f, 1.0f, 0.0f});
+
+    // upload model matrix to shader
+    glUniformMatrix4fv(state->shader.modelMatrixLocation, 1, GL_FALSE, *state->pyramidModel);
+    mesh_draw(&state->triangle_mesh);
+
+    glUniformMatrix4fv(state->shader.modelMatrixLocation, 1, GL_FALSE, *orbitModel);
+    mesh_draw(&state->triangle_mesh);
+
+    // swap front and back buffers to display rendered frame
+    SDL_GL_SwapWindow(window);
+
+    return SDL_APP_CONTINUE;
+}
+
+/* This function runs once at shutdown. */
+void SDL_AppQuit(void *appstate, SDL_AppResult result)
+{
+    Engine_Data *state = (Engine_Data *)appstate;
+
+    // cleanup all resources
+    if (state) {
+        mesh_delete(&state->triangle_mesh);
+
+        if (state->shader.ID != 0) {
+            shader_delete(&state->shader);
+        }
+
+        free(state);
+    }
+
+    if (gl_context) {
+        SDL_GL_DestroyContext(gl_context);
+    }
+
+    if (window) {
+        SDL_DestroyWindow(window);
+    }
+
+    log_info("Application quit and resources cleaned up");
+}