Koru

A lightweight, multi-platform game engine built in C using the Vulkan graphics API.

Koru is designed to be fast, portable, and easy to extend — providing a low-level foundation for game development across platforms including Windows, Linux, and soon consoles and mobile devices.

🧠 What Is Koru?

Koru is a C99-based game engine focused on performance, portability, and modularity. It's ideal for developers who want fine-grained control over rendering, input, memory, and platform-specific functionality without the overhead of high-level abstractions.

External libs (/engine/src/vendor/)

stb-image.h - From STB by Sean Barrett - Lightweight way to handle and load images

🚀 Features:

Written entirely in C99 – minimal dependencies
Vulkan-based renderer for high-performance graphics
Cross-platform: Windows, Linux, Mac (with future plans for consoles and mobile)
Modular architecture for easy extension
Custom memory allocators, logging, assertions, and data structures etc

🖼 Architecture

The high-level architecture of Koru is divided into four main layers:

1. Platform Layer

Handles OS-specific functionality:

Windowing: Creates and manages windows on Windows/Linux/Mac.
Input: Manages keyboard, mouse, and gamepad input.
File I/O: Provides cross-platform file system access.
Console Output: Handles logging and debugging output.
Memory Management: Allocates and frees memory efficiently.
Renderer API Extensions: Integrates with Vulkan for rendering.

2. Core

Provides fundamental utilities and services:

Logger: Logs messages for debugging and monitoring.
Assertions: Ensures correctness during development.
Data Structures: Efficient containers like dynamic arrays, linked lists, etc.
Memory Allocators: Custom allocators for optimized memory usage.
Math Library: Vector, matrix, and quaternion operations.
Parsers: Parses formats like XML, CSV, JSON, etc.
Engine Configuration: Loads and manages engine settings.
Profiling: Measures performance bottlenecks.
Async File I/O: Asynchronous file operations for non-blocking I/O.
Localization: Supports internationalization.
String Library: String manipulation utilities.
Random Number Generator (RNG): Generates random numbers for simulations and AI.

3. Resource Management

Manages various assets:

Images: Texture loading and caching.
Materials: Shader and lighting configurations.
Meshes: 3D model loading and processing.
Animations: Skeletal animations and timeline systems.
World Maps: Terrain and level data management.

4. Application Layer

Contains higher-level systems:

Renderer Front End: GUI, camera management, post-processing effects.
Renderer Back End: Scene graph, materials, shaders, meshes, textures.
Audio: 2D/3D audio playback, effects, and spatial audio.
Others: Animation/timelines, event system, ECS, state machines, collision/physics.

📋 Feature List

Here’s a summary of the features to be implemented in v0.1:

Core Features

Lightweight build system: Simple scripts for compiling on Windows and Linux.
Low-level utilities:
- Dynamic arrays
- String handling
- Memory allocators
- Profiling tools
- Assertions
- Logging
Platform layer:
- Window creation and management
- Input handling (keyboard, mouse, gamepad)
- File I/O
- Console output
Renderer/API Abstraction Layer: Uses Vulkan for cross-platform rendering.
Memory Management: Custom allocators for efficient memory use.
Scenegraph/ECS: Hierarchical scene management and entity-component-system architecture.
Profiling/Debugging utilities: Tools for measuring performance and identifying bottlenecks.
"Scripting" support via hot reloading: Experimental support for scripting through hot-reloading mechanisms.

Planned Features

Mobile and console support
Full audio subsystem
Physics and collision detection
Advanced animation system
Improved asset pipeline

🎨 Visuals

Check out the diagrams included in the assets/ folder to understand how everything fits together:

Diagram	Description
	High-level overview of system modules and interactions
	File structure and module organization
	Summary of current capabilities and roadmap

📁 Project Structure

.
├── assets
│   ├── Koru Engine Architecture.png
│   ├── Koru Project Structure.png
│   ├── Koru v0.1 Feature List.png
│   └── shaders
│       ├── Builtin.ObjectShader.frag.glsl
│       └── Builtin.ObjectShader.vert.glsl
├── bin
│   ├── assets
│   │   ├── Koru Engine Architecture.png
│   │   ├── Koru Project Structure.png
│   │   ├── Koru v0.1 Feature List.png
│   │   └── shaders
│   │       ├── Builtin.ObjectShader.frag.glsl
│   │       ├── Builtin.ObjectShader.frag.spv
│   │       ├── Builtin.ObjectShader.vert.glsl
│   │       └── Builtin.ObjectShader.vert.spv
│   ├── console.log
│   ├── libengine.so
│   ├── testbed
│   └── tests
├── build-all.bat
├── build-all.sh
├── clean-all.bat
├── clean-all.sh
├── Doxyfile                                # Configuration for generating API documentation with Doxygen
├── engine
│   ├── build.bat                           # Windows: Builds engine DLL
│   ├── build.sh                            # Linux: Builds engine shared object (.so)
│   └── src
│       ├── containers
│       │   ├── darray.c                    # Implementation of dynamic array container
│       │   └── darray.h                    # Public interface for dynamic arrays
│       ├── core
│       │   ├── application.c               # Application lifecycle implementation (init/run/shutdown)
│       │   ├── application.h               # Public interface for the application system
│       │   ├── asserts.h                   # Custom assertion macros and debugging utilities
│       │   ├── clock.c
│       │   ├── clock.h
│       │   ├── event.c                     # Event system implementation (register/unregister/fire)
│       │   ├── event.h                     # Public interface for event handling system
│       │   ├── input.c
│       │   ├── input.h
│       │   ├── kmemory.c                   # Memory allocation system with tagging support
│       │   ├── kmemory.h                   # Interface for tagged memory management
│       │   ├── kstring.c
│       │   ├── kstring.h
│       │   ├── logger.c                    # Logging system with color-coded output
│       │   └── logger.h                    # Public interface for logging module
│       ├── defines.h                       # Common type definitions, macros, and platform detection
│       ├── entry.h                         # Entry point interface; declares create_game()
│       ├── game_types.h                    # Game-related types used across engine and game logic
│       ├── math
│       │   ├── kmath.c
│       │   ├── kmath.h
│       │   └── math_types.h
│       ├── memory
│       │   ├── linear_allocator.c
│       │   └── linear_allocator.h
│       ├── platform
│       │   ├── filesystem.c
│       │   ├── filesystem.h
│       │   ├── platform_android.c
│       |   ├── platform.h                 # Platform abstraction layer interface
│       │   ├── platform_ios.c
│       │   ├── platform_linux.c           # Linux-specific implementation of platform functions
│       │   ├── platform_macos.c
│       │   └── platform_win32.c           # Windows-specific implementation of platform functions
│       └── renderer
│           ├── renderer_backend.c
│           ├── renderer_backend.h
│           ├── renderer_frontend.c
│           ├── renderer_frontend.h
│           ├── renderer_types.inl
│           └── vulkan
│               ├── shaders
│               │   ├── vulkan_object_shader.c
│               │   └── vulkan_object_shader.h
│               ├── vulkan_backend.c
│               ├── vulkan_backend.h
│               ├── vulkan_buffer.c
│               ├── vulkan_buffer.h
│               ├── vulkan_command_buffer.c
│               ├── vulkan_command_buffer.h
│               ├── vulkan_device.c
│               ├── vulkan_device.h
│               ├── vulkan_fence.c
│               ├── vulkan_fence.h
│               ├── vulkan_framebuffer.c
│               ├── vulkan_framebuffer.h
│               ├── vulkan_image.c
│               ├── vulkan_image.h
│               ├── vulkan_pipeline.c
│               ├── vulkan_pipeline.h
│               ├── vulkan_platform.h
│               ├── vulkan_renderpass.c
│               ├── vulkan_renderpass.h
│               ├── vulkan_shader_utils.c
│               ├── vulkan_shader_utils.h
│               ├── vulkan_swapchain.c
│               ├── vulkan_swapchain.h
│               ├── vulkan_types.inl
│               ├── vulkan_utils.c
│               └── vulkan_utils.h
├── LICENSE                                 # MIT License file
├── Makefile.engine.linux.mak
├── Makefile.engine.windows.mak
├── Makefile.testbed.linux.mak
├── Makefile.testbed.windows.mak
├── post-build.bat
├── post-build.sh
├── README.md                               # This file - main project overview and guide
├── testbed
|   ├── build.bat                           # Windows: Builds testbed application
|   ├── build.sh                            # Linux: Builds testbed application
|   └── src
|       ├── entry.c                         # Entry point for testbed app; implements create_game()
|       ├── game.c                          # Testbed game logic (initialize/update/render stubs)
|       └── game.h                          # Interface for testbed game implementation
└── tests
    ├── build.bat
    ├── build.sh
    └── src
        ├── expect.h
        ├── main.c
        ├── memory
        │   ├── linear_allocator_tests.c
        │   └── linear_allocator_tests.h
        ├── test_manager.c
        └── test_manager.h

37 directories, 176 files

⚙️ Build Scripts/Instructions

Check tasks.json for sequence:

File	Purpose	Notes
`engine/build.sh`	Builds engine `.so` (shared lib) on Linux	Uses Vulkan/XCB/X11
`engine/build.bat`	Builds engine `.dll` on Windows	Links with Vulkan SDK
`testbed/build.sh`	Builds testbed app using engine `.so` on Linux	Sets RPATH for easy loading
`testbed/build.bat`	Builds testbed `.exe` using engine `.dll` on Windows	Links `.lib` import library
`build-all.sh`	Runs all Linux builds sequentially	Checks for errors
`build-all.bat`	Runs all Windows builds sequentially	Same as above but for Windows

Linux

Make sure Clang and the Vulkan SDK are installed. Alternatively install VSCode and run the debugger (Commonly F5, and run the engine)

# Give execution permissions
chmod +x build-all.sh

# Run the build
./build-all.sh

The output will be placed in bin/:

libengine.so – The engine shared library
testbed – The testbed executable

Windows

Ensure:

Clang is available
Vulkan SDK is installed and VULKAN_SDK environment variable is set
VS Code makes it easy to run the tasks in the .vscode/tasks.json file.

Then run:

build-all.bat

Building Docs

To generate our Doxygen documentation, run:

    doxygen Doxyfile

Output files:

bin\engine.dll
bin\testbed.exe

🔮 Roadmap

Plans to expand Koru include:

✅ Rendering Layer
- Vulkan renderer initialization
- Swapchain setup
- Command buffers, pipelines, shaders
✅ Input System
- Keyboard/mouse/gamepad support
- Input mapping and event system
✅ Asset Management
- Texture loader
- Mesh format and loader
- Material system
✅ Audio System
- Basic sound playback
- Cross-platform audio backend
✅ Multi-Platform Support
- Console (PlayStation, Xbox, Switch)
- Mobile (Android/iOS)
✅ Editor Tools
- Simple scene editor
- Asset pipeline tools

💡 Want to Help?

Contributions are welcome! Whether you're interested in:

Writing documentation
Implementing new features
Fixing bugs
Improving tooling or build scripts

Feel free to open an issue or PR!

📄 License

This project is licensed under the MIT License – see the LICENSE file for details.


## 🚀 Next Steps

TO-DO: Add:

- ✅ A **Getting Started Guide** (`docs/getting-started.md`)
- ✅ A **Contribution Guide** (`CONTRIBUTING.md`)
- ✅ A **Code of Conduct** (`CODE_OF_CONDUCT.md`)
- ✅ GitHub Actions for CI builds (optional)

🎮 Koru Engine – Rendering System (Vulkan)

A deep dive into how Koru sets up its Vulkan-based rendering system — from instance creation to frame submission.

Koru is a low-level game engine written in C99 that uses the Vulkan graphics API for rendering. This document explains the entire rendering pipeline setup used in Koru, including:

Instance creation
Physical device selection
Logical device creation
Surface & swapchain setup
Render passes
Framebuffers
Command buffers

This guide assumes some basic knowledge of C and Vulkan concepts. If you're new to Vulkan, this will help understand what’s happening behind the scenes as you run the testbed.

🧠 Why Use Vulkan?

Vulkan gives developers explicit control over GPU operations. It allows fine-grained access to queues, memory, and rendering pipelines — which is great for performance, but comes at the cost of complexity.

Koru abstracts much of that complexity using a modular architecture, allowing you to build a rendering system step-by-step without needing to manage everything manually every time.

📦 High-Level Architecture (Render Layer)

+------------------+
|   Application    |
|     Logic        |
|  (game.c)        |
+------------------+
         |
         v
+------------------+
|   Renderer       |
|   Frontend       |
| (renderer_frontend.h/c) |
+------------------+
         |
         v
+------------------+
|   Platform       |
|   Abstraction    |
| (platform_linux.c)|
+------------------+
         |
         v
+------------------+
|   Vulkan         |
|   Device         |
| (vulkan_device.c/h) |
+------------------+
         |
         v
+------------------+
|   Swapchain      |
|   Management     |
| (vulkan_swapchain.c/h) |
+------------------+
         |
         v
+------------------+
|   Render Pass /  |
|   Framebuffer    |
| (vulkan_renderpass.c/h) |
+------------------+
         |
         v
+------------------+
|   Image          |
|   Management     |
| (vulkan_image.c/h) |
+------------------+
         |
         v
+------------------+
|   Command Buffer |
|   Submission     |
| (renderer_frontend.c) |
+------------------+

This shows how each module fits into the overall rendering flow.

🛠️ The Full Rendering Setup Process

Let’s walk through each stage of the rendering setup process, with real code examples from the engine.

1. 🧱 Create Vulkan Instance

The first thing to do is creating a VkInstance — this connects the app to the Vulkan library.

// From vulkan_renderer_backend_initialize()
VkApplicationInfo app_info = {VK_STRUCTURE_TYPE_APPLICATION_INFO};
app_info.apiVersion = VK_MAKE_API_VERSION(0, 1, 4, 0);
app_info.pApplicationName = application_name;
app_info.applicationVersion = VK_MAKE_API_VERSION(0, 0, 0, 1);
app_info.pEngineName = "Koru Engine";
app_info.engineVersion = VK_MAKE_API_VERSION(0, 0, 0, 1);

VkInstanceCreateInfo create_info = {VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO};
create_info.pApplicationInfo = &app_info;

const char** required_extensions = darray_create(const char*);
darray_push(required_extensions, &VK_KHR_SURFACE_EXTENSION_NAME);
platform_get_required_extension_names(&required_extensions);

create_info.enabledExtensionCount = darray_length(required_extensions);
create_info.ppEnabledExtensionNames = required_extensions;

// Enable validation layers if _DEBUG is defined
#if defined(_DEBUG)
    create_info.enabledLayerCount = required_validation_layer_count;
    create_info.ppEnabledLayerNames = required_validation_layer_names;
#endif

VK_CHECK(vkCreateInstance(&create_info, context.allocator, &context.instance));

✅ This creates the main connection to Vulkan, enabling extensions and validation layers.

2. 🖥 Create Window Surface

Next, to create a surface — this is what connects the window to the GPU.

In Linux:

// platform_linux.c
xcb_intern_atom_reply_t* wm_delete_reply = xcb_intern_atom_reply(...);
state->wm_delete_win = wm_delete_reply->atom;

// Create surface
VkXcbSurfaceCreateInfoKHR surface_create_info = {VK_STRUCTURE_TYPE_XCB_SURFACE_CREATE_INFO_KHR};
surface_create_info.connection = state->connection;
surface_create_info.window = state->window;

vkCreateXcbSurfaceKHR(context->instance, &surface_create_info, context->allocator, &context->surface);

In Windows: The engine uses vkCreateWin32SurfaceKHR() instead.

✅ A surface is essential because it defines where rendered frames go usually the screen or a window.

3. 🔍 Query Physical Devices

Once an instance and a surface are ready, query available GPUs:

// vulkan_device.c
u32 physical_device_count = 0;
VK_CHECK(vkEnumeratePhysicalDevices(context->device.physical_device, &physical_device_count, 0));

VkPhysicalDevice physical_devices[physical_device_count];
VK_CHECK(vkEnumeratePhysicalDevices(context->instance, &physical_device_count, physical_devices));

Then select one that meets requirements:

for (u32 i = 0; i < physical_device_count; ++i) {
    VkPhysicalDeviceProperties properties;
    vkGetPhysicalDeviceProperties(physical_devices[i], &properties);

    VkPhysicalDeviceFeatures features;
    vkGetPhysicalDeviceFeatures(physical_devices[i], &features);

    // Check queue family support
    vulkan_physical_device_queue_family_info queue_info = {};
    vulkan_swapchain_support_info swapchain_support = {};

    b8 result = physical_device_meets_requirements(
        physical_devices[i],
        context->surface,
        &properties,
        &features,
        &requirements,
        &queue_info,
        &swapchain_support);
}

🔍 Requirements include:

Graphics/Compute/Present/Transfer queues
Extensions like VK_KHR_SWAPCHAIN_EXTENSION_NAME
Features like samplerAnisotropy
Prefer discrete GPU (optional)

4. 🔄 Create Logical Device

After selecting a suitable physical device, create a logical device to interface with the GPU.

// vulkan_device.c
b8 present_shares_graphics_queue = (context->device.graphics_queue_index == context->device.present_queue_index);
b8 transfer_shares_graphics_queue = (context->device.graphics_queue_index == context->device.transfer_queue_index);

u32 index_count = 1;
if (!present_shares_graphics_queue) index_count++;
if (!transfer_shares_graphics_queue) index_count++;

u32 indices[index_count];
indices[0] = context->device.graphics_queue_index;
...

Define the queues as needed:

VkDeviceQueueCreateInfo queue_create_infos[index_count];
for (u32 i = 0; i < index_count; ++i) {
    queue_create_infos[i].sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO;
    queue_create_infos[i].queueFamilyIndex = indices[i];
    queue_create_infos[i].queueCount = 1;
    f32 queue_priority = 1.0f;
    queue_create_infos[i].pQueuePriorities = &queue_priority;
}

Finally, create the logical device:

VkDeviceCreateInfo device_create_info = {VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO};
device_create_info.queueCreateInfoCount = index_count;
device_create_info.pQueueCreateInfos = queue_create_infos;
device_create_info.pEnabledFeatures = &device_features;

VK_CHECK(vkCreateDevice(context->device.physical_device, &device_create_info, context->allocator, &context->device.logical_device));

✅ This creates a way to submit commands to the GPU.

5. ⏱ Get Queues

Once the device is created, get handles to the actual queues:

vkGetDeviceQueue(context->device.logical_device, context->device.graphics_queue_index, 0, &context->device.graphics_queue);
vkGetDeviceQueue(context->device.logical_device, context->device.present_queue_index, 0, &context->device.present_queue);

These are used later to:

Submit draw commands (graphics_queue)
Present frames (present_queue)
Copy data (transfer_queue)

6. 🔄 Query Swapchain Support

Before creating a swapchain, check what formats and modes are supported:

// vulkan_device.c
void vulkan_device_query_swapchain_support(...) {
    vkGetPhysicalDeviceSurfaceCapabilitiesKHR(device, surface, &out_support->capabilities);
    vkGetPhysicalDeviceSurfaceFormatsKHR(device, surface, &out_support->format_count, 0);
    vkGetPhysicalDeviceSurfacePresentModesKHR(device, surface, &out_support->present_mode_count, 0);
}

This helps choose the best image format and presentation mode.

7. 🔁 Create Swapchain

Now create the swapchain based on what the device supports:

// vulkan_swapchain.c
VkSwapchainCreateInfoKHR create_info = {VK_STRUCTURE_TYPE_SWAPCHAIN_CREATE_INFO_KHR};
create_info.surface = context->surface;
create_info.minImageCount = image_count;
create_info.imageFormat = swapchain->image_format.format;
create_info.imageExtent = swapchain_extent;
create_info.imageUsage = VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT;

if (context->device.graphics_queue_index != context->device.present_queue_index) {
    u32 queueFamilyIndices[] = {
        (u32)context->device.graphics_queue_index,
        (u32)context->device.present_queue_index};

    create_info.imageSharingMode = VK_SHARING_MODE_CONCURRENT;
    create_info.queueFamilyIndexCount = 2;
    create_info.pQueueFamilyIndices = queueFamilyIndices;
} else {
    create_info.imageSharingMode = VK_SHARING_MODE_EXCLUSIVE;
}

VK_CHECK(vkCreateSwapchainKHR(context->device.logical_device, &create_info, context->allocator, &swapchain->handle));

🔄 The swapchain acts like a rotating carousel of images:

One is being drawn
One is being displayed
One is waiting to be used next

This avoids tearing and ensures smooth rendering.

8. 🖼 Create Image Views

Each image in the swapchain needs a view so the GPU can interpret it:

for (u32 i = 0; i < swapchain->image_count; ++i) {
    VkImageViewCreateInfo view_info = {VK_STRUCTURE_TYPE_IMAGE_VIEW_CREATE_INFO};
    view_info.image = swapchain->images[i];
    view_info.viewType = VK_IMAGE_VIEW_TYPE_2D;
    view_info.format = swapchain->image_format.format;
    view_info.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
    view_info.subresourceRange.baseMipLevel = 0;
    view_info.subresourceRange.levelCount = 1;
    view_info.subresourceRange.baseArrayLayer = 0;
    view_info.layerCount = 1;

    VK_CHECK(vkCreateImageView(context->device.logical_device, &view_info, context->allocator, &swapchain->views[i]));
}

🖼 Each image view wraps a raw VkImage, defining how it's accessed (e.g., color attachment, depth buffer).

9. 🧊 Detect Depth Format

For depth testing, a compatible depth format is needed:

b8 vulkan_device_detect_depth_format(vulkan_device* device) {
    const u64 candidate_count = 3;
    VkFormat candidates[candidate_count] = {
        VK_FORMAT_D32_SFLOAT,
        VK_FORMAT_D32_SFLOAT_S8_UINT,
        VK_FORMAT_D24_UNORM_S8_UINT};

    for (u64 i = 0; i < candidate_count; ++i) {
        VkFormatProperties props;
        vkGetPhysicalDeviceFormatProperties(device->physical_device, candidates[i], &props);

        if ((props.optimalTilingFeatures & VK_FORMAT_FEATURE_DEPTH_STENCIL_ATTACHMENT_BIT)) {
            device->depth_format = candidates[i];
            return True;
        }
    }

    KERROR("No supported depth format found.");
    return False;
}

🧃 Once selected, create a depth/stencil image and its view.

10. 🎨 Create Render Pass

The render pass defines how rendering works — what attachments to use, how they behave, and what subpasses exist.

// vulkan_renderpass.c
VkAttachmentDescription attachments[2] = {};
attachments[0].format = swapchain->image_format.format;
attachments[0].loadOp = VK_ATTACHMENT_LOAD_OP_CLEAR;
attachments[0].storeOp = VK_ATTACHMENT_STORE_OP_STORE;
attachments[0].stencilLoadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE;
attachments[0].initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;
attachments[0].finalLayout = VK_IMAGE_LAYOUT_PRESENT_SRC_KHR;

attachments[1].format = context->device.depth_format;
attachments[1].loadOp = VK_ATTACHMENT_LOAD_OP_CLEAR;
attachments[1].storeOp = VK_ATTACHMENT_STORE_OP_DONT_CARE;
attachments[1].initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;
attachments[1].finalLayout = VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL;

VkSubpassDescription subpass = {};
subpass.pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS;
subpass.colorAttachmentCount = 1;
subpass.pColorAttachments = &color_ref;
subpass.pDepthStencilAttachment = &depth_stencil_ref;

VkRenderPassCreateInfo info = {};
info.sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO;
info.attachmentCount = 2;
info.pAttachments = attachments;
info.subpassCount = 1;
info.pSubpasses = &subpass;

VK_CHECK(vkCreateRenderPass(context->device.logical_device, &info, context->allocator, &renderpass->handle));

🎨 The render pass is like a blueprint — it tells the GPU:

What kind of data it will write to
How to handle clearing and storing it
What layout transitions happen between steps

11. 🖼 Create Framebuffers

Framebuffers combine images and render passes:

VkFramebufferCreateInfo fb_info = {VK_STRUCTURE_TYPE_FRAMEBUFFER_CREATE_INFO};
fb_info.renderPass = renderpass->handle;
fb_info.attachmentCount = 2;
fb_info.pAttachments = attachments;
fb_info.width = width;
fb_info.height = height;
fb_info.layers = 1;

VK_CHECK(vkCreateFramebuffer(device, &fb_info, 0, &framebuffer));

🖼 Each framebuffer links:

A color image from the swapchain
A depth/stencil image
The render pass that defines how to use them

12. 🗂 Command Buffers and Submission

Command buffers store drawing commands:

// Begin command recording
VkCommandBufferBeginInfo begin_info = {VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO};
vkBeginCommandBuffer(command_buffer, &begin_info);

// Record draw commands here...

vkEndCommandBuffer(command_buffer);

Then submit to the GPU:

VkSubmitInfo submit_info = {VK_STRUCTURE_TYPE_SUBMIT_INFO};
submit_info.waitSemaphoreCount = 1;
submit_info.pWaitSemaphores = &image_available_semaphore;
submit_info.commandBufferCount = 1;
submit_info.pCommandBuffers = &command_buffer;

VK_CHECK(vkQueueSubmit(graphics_queue, 1, &submit_info, fence));

And finally present:

VkPresentInfoKHR present_info = {VK_STRUCTURE_TYPE_PRESENT_INFO_KHR};
present_info.swapchainCount = 1;
present_info.pSwapchains = &swapchain->handle;
present_info.pImageIndices = &image_index;

VkResult result = vkQueuePresentKHR(present_queue, &present_info);

🧩 Diagram: Full Rendering Flow

+-------------------+
|   Application     |
|   Entry Point     |
| (application_run())|
+-------------------+
           |
           v
+-------------------+
|   Create Instance |
| (vkCreateInstance)|
+-------------------+
           |
           v
+-------------------+
|   Create Surface  |
| (vkCreateXcbSurfaceKHR) |
+-------------------+
           |
           v
+-------------------+
| Enumerate Physical|
| Devices           |
| (vkEnumeratePhysicalDevices) |
+-------------------+
           |
           v
+-------------------+
| Select Suitable   |
| Physical Device   |
| (select_physical_device) |
+-------------------+
           |
           v
+-------------------+
| Create Logical    |
| Device            |
| (vkCreateDevice)  |
+-------------------+
           |
           v
+-------------------+
| Get Queue Handles |
| (vkGetDeviceQueue) |
+-------------------+
           |
           v
+-------------------+
| Query Swapchain   |
| Support           |
| (vkGetPhysicalDeviceSurface*) |
+-------------------+
           |
           v
+-------------------+
| Create Swapchain  |
| (vkCreateSwapchainKHR) |
+-------------------+
           |
           v
+-------------------+
| Create Image Views|
| (vkCreateImageView) |
+-------------------+
           |
           v
+-------------------+
| Detect Depth      |
| Format            |
| (vulkan_device_detect_depth_format) |
+-------------------+
           |
           v
+-------------------+
| Create Depth Image|
| (vulkan_image_create) |
+-------------------+
           |
           v
+-------------------+
| Create Render Pass|
| (vkCreateRenderPass) |
+-------------------+
           |
           v
+-------------------+
| Create Framebuffer|
| (vkCreateFramebuffer) |
+-------------------+
           |
           v
+-------------------+
| Begin Main Loop   |
| (vkAcquireNextImageKHR) |
+-------------------+
           |
           v
+-------------------+
| Begin Render Pass |
| (vkCmdBeginRenderPass) |
+-------------------+
           |
           v
+-------------------+
| Record Draw       |
| Commands          |
+-------------------+
           |
           v
+-------------------+
| End Render Pass   |
| (vkCmdEndRenderPass) |
+-------------------+
           |
           v
+-------------------+
| Submit Command    |
| Buffer to GPU     |
| (vkQueueSubmit)   |
+-------------------+
           |
           v
+-------------------+
| Present Frame     |
| (vkQueuePresentKHR) |
+-------------------+

This is the full rendering loop that happens every frame.

🧰 Key Structures Used

`vulkan_context`

Tracks global Vulkan state:

typedef struct vulkan_context {
    VkInstance instance;
    VkSurfaceKHR surface;
    VkDebugUtilsMessengerEXT debug_messenger;
    vulkan_device device;
    vulkan_swapchain swapchain;
    u32 image_index;
    u32 current_frame;
    b8 recreating_swapchain;
    i32 (*find_memory_index)(...);
} vulkan_context;

`vulkan_device`

Holds physical/logical device and queue info:

typedef struct vulkan_device {
    VkPhysicalDevice physical_device;
    VkDevice logical_device;
    vulkan_swapchain_support_info swapchain_support;
    i32 graphics_queue_index;
    i32 present_queue_index;
    i32 transfer_queue_index;
    VkQueue graphics_queue;
    VkQueue present_queue;
    VkQueue transfer_queue;
    VkPhysicalDeviceProperties properties;
    VkPhysicalDeviceFeatures features;
    VkPhysicalDeviceMemoryProperties memory;
    VkFormat depth_format;
} vulkan_device;

`vulkan_swapchain`

Manages images and depth buffer:

typedef struct vulkan_swapchain {
    VkSurfaceFormatKHR image_format;
    u8 max_frames_in_flight;
    VkSwapchainKHR handle;
    u32 image_count;
    VkImage* images;
    VkImageView* views;
    vulkan_image depth_attachment;
} vulkan_swapchain;

`vulkan_renderpass`

Defines clear values and viewport settings:

typedef struct vulkan_renderpass {
    VkRenderPass handle;
    f32 clear_r, clear_g, clear_b, clear_a;
    f32 clear_depth;
    u32 clear_stencil;
    f32 viewport_x, viewport_y, viewport_w, viewport_h;
    f32 scissor_x, scissor_y, scissor_w, scissor_h;
} vulkan_renderpass;

💡 Why All This Is Needed

Vulkan is explicit by design. Every operation must be described precisely. Here's why each part matters:

Component	Purpose
Instance	Connects app to Vulkan driver
Surface	Links window to GPU output
Physical Device	Represents the actual GPU
Logical Device	Interface to the GPU
Queues	Workers for graphics/present/transfer
Swapchain	Manages sequence of renderable images
Images	Raw GPU memory to draw into
Image Views	Define how to read/write those images
Render Pass	Defines rendering rules (clear/store ops, layout)
Framebuffers	Combine images into something you can draw into
Command Buffers	Store GPU commands to execute later

🧱 Summary Table

Module	Responsibility
`vulkan_renderer_backend_initialize()`	Creates instance, surface, and starts device setup
`vulkan_device_create()`	Selects physical device, creates logical device
`vulkan_device_query_swapchain_support()`	Queries device capabilities for swapchain
`vulkan_swapchain_create()`	Initializes the swapchain and image views
`vulkan_device_detect_depth_format()`	Finds a usable depth format
`vulkan_renderpass_create()`	Sets up how we render
`vulkan_command_buffer_begin()`	Starts recording draw commands
`vulkan_swapchain_present()`	Presents the final image to the screen

🧪 Bonus: Sample Code for Acquiring an Image

b8 vulkan_swapchain_acquire_next_image_index(...) {
    VkResult result = vkAcquireNextImageKHR(
        context->device.logical_device,
        swapchain->handle,
        timeout_ns,
        image_available_semaphore,
        fence,
        out_image_index);

    if (result == VK_ERROR_OUT_OF_DATE_KHR) {
        vulkan_swapchain_recreate(context, width, height, swapchain);
        return False;
    } else if (result != VK_SUCCESS && result != VK_SUBOPTIMAL_KHR) {
        KFATAL("Failed to acquire swapchain image!");
        return False;
    }

    return True;
}

This function gets the next image from the swapchain — and triggers recreation if needed.

🚫 Common Errors and Fixes

❌ `VK_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_EXT`: No cache file

Not critical — just means the shader cache doesn't exist yet.

Name		Name	Last commit message	Last commit date
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.github/workflows		.github/workflows
.vscode		.vscode
assets		assets
docs		docs
engine		engine
html		html
latex		latex
testbed		testbed
tests		tests
.clangd		.clangd
.gitignore		.gitignore
Doxyfile		Doxyfile
LICENSE		LICENSE
Makefile.engine.linux.mak		Makefile.engine.linux.mak
Makefile.engine.windows.mak		Makefile.engine.windows.mak
Makefile.testbed.linux.mak		Makefile.testbed.linux.mak
Makefile.testbed.windows.mak		Makefile.testbed.windows.mak
README.md		README.md
build-all.bat		build-all.bat
build-all.sh		build-all.sh
clean-all.bat		clean-all.bat
clean-all.sh		clean-all.sh
post-build.bat		post-build.bat
post-build.sh		post-build.sh

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Koru

🧠 What Is Koru?

External libs (/engine/src/vendor/)

🚀 Features:

🖼 Architecture

1. Platform Layer

2. Core

3. Resource Management

4. Application Layer

📋 Feature List

Core Features

Planned Features

🎨 Visuals

📁 Project Structure

⚙️ Build Scripts/Instructions

Linux

Windows

Building Docs

🔮 Roadmap

💡 Want to Help?

📄 License

🎮 Koru Engine – Rendering System (Vulkan)

🧠 Why Use Vulkan?

📦 High-Level Architecture (Render Layer)

🛠️ The Full Rendering Setup Process

1. 🧱 Create Vulkan Instance

2. 🖥 Create Window Surface

3. 🔍 Query Physical Devices

4. 🔄 Create Logical Device

5. ⏱ Get Queues

6. 🔄 Query Swapchain Support

7. 🔁 Create Swapchain

8. 🖼 Create Image Views

9. 🧊 Detect Depth Format

10. 🎨 Create Render Pass

11. 🖼 Create Framebuffers

12. 🗂 Command Buffers and Submission

🧩 Diagram: Full Rendering Flow

🧰 Key Structures Used

vulkan_context

vulkan_device

vulkan_swapchain

vulkan_renderpass

💡 Why All This Is Needed

🧱 Summary Table

🧪 Bonus: Sample Code for Acquiring an Image

🚫 Common Errors and Fixes

❌ VK_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_EXT: No cache file

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`vulkan_context`

`vulkan_device`

`vulkan_swapchain`

`vulkan_renderpass`

❌ `VK_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_EXT`: No cache file

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