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= Hello Triangle with Vulkan 1.3 Features using Vulkan-Hpp
ifdef::site-gen-antora[]
TIP: The source for this sample can be found in the https://github.com/KhronosGroup/Vulkan-Samples/tree/main/samples/api/hpp_hello_triangle_1_3[Khronos Vulkan samples github repository].
endif::[]
NOTE: A transcoded version of the API sample https://github.com/KhronosGroup/Vulkan-Samples/tree/main/samples/api/hello_triangle_1_3[Hello Triangle 1.3] that illustrates the usage of the C{pp} bindings of Vulkan provided by Vulkan-Hpp.
This sample demonstrates how to render a simple triangle using Vulkan 1.3 core features. It modernizes the traditional "Hello Triangle" Vulkan sample by incorporating:
- **Dynamic Rendering**
- **Synchronization2**
- **Extended Dynamic State**
- **Vertex Buffers**
## Overview
The sample renders a colored triangle to the screen using Vulkan 1.3. It showcases how to:
- Initialize Vulkan with Vulkan 1.3 features enabled.
- Use dynamic rendering to simplify the rendering pipeline.
- Employ the Synchronization2 API for improved synchronization.
- Utilize extended dynamic states to reduce pipeline complexity.
- Manage vertex data using vertex buffers instead of hard-coded vertices.
## Key Features
### 1. Dynamic Rendering
**What is Dynamic Rendering?**
Dynamic Rendering is a feature introduced in Vulkan 1.3 that allows rendering without pre-defined render passes and framebuffers. It simplifies the rendering process by enabling you to specify rendering states directly during command buffer recording.
**How It's Used in the Sample:**
- **No Render Passes or Framebuffers:** The sample does not create `vk::RenderPass` or `vk::Framebuffer` objects.
- **`vk::CommandBuffer::beginRendering()` and `vk::CommandBuffer::endRendering()`:** These functions are used to begin and end rendering operations dynamically.
- **Pipeline Creation:** Uses `vk::PipelineRenderingCreateInfo` during pipeline creation to specify rendering details.
**Benefits:**
- Simplifies code by reducing boilerplate associated with render passes and framebuffers.
- Increases flexibility by allowing rendering to different attachments without recreating render passes.
### 2. Synchronization2
**What is Synchronization2?**
Synchronization2 is an improved synchronization API introduced in Vulkan 1.3. It provides more granular control over synchronization primitives and simplifies the synchronization process.
**How It's Used in the Sample:**
- **`vk::CommandBuffer::pipelineBarrier2()`:** Replaces the older `vk::CommandBuffer::pipelineBarrier()` for more detailed synchronization.
- **`vk::DependencyInfo` and `vk::ImageMemoryBarrier2`:** Used to specify precise memory dependencies and image layout transitions.
**Example Usage:**
```cpp
vk::ImageMemoryBarrier2 image_barrier = {
// ... members ...
};
vk::DependencyInfo dependency_info = {
.imageMemoryBarrierCount = 1,
.pImageMemoryBarriers = &image_barrier,
};
cmd.pipelineBarrier2(dependency_info);
```
**Benefits:**
- Provides more expressive and flexible synchronization.
- Reduces the potential for synchronization errors.
- Simplifies the specification of pipeline stages and access masks.
### 3. Extended Dynamic State
**What is Extended Dynamic State?**
Extended Dynamic State allows more pipeline states to be set dynamically at command buffer recording time rather than during pipeline creation. This reduces the number of pipeline objects needed.
**How It's Used in the Sample:**
- **Dynamic States Enabled:** The sample enables dynamic states like `vk::DynamicState::eCullMode`, `vk::DynamicState::eFrontFace`, and `vk::DynamicState::ePrimitiveTopology`.
- **Dynamic State Commands:** Uses `vk::CommandBuffer::setCullMode()`, `vk::CommandBuffer::setFrontFace()`, and `vk::CommandBuffer::setPrimitiveTopology()` to set these states dynamically.
**Example Usage:**
```cpp
cmd.setCullMode(vk::DynamicState::eCullMode);
cmd.setFrontFace(vk::FrontFace::eClockwise);
cmd.setPrimitiveTopology(vk::PrimitiveTopology::eTriangleList);
```
**Benefits:**
- Reduces the need to create multiple pipelines for different state configurations.
- Enhances flexibility by allowing state changes without pipeline recreation.
### 4. Vertex Buffers
**What Changed?**
Unlike the original sample, which used hard-coded vertices in the shader, this sample uses a vertex buffer to store vertex data.
**How It's Used in the Sample:**
- **Vertex Structure Defined:**
```cpp
struct Vertex {
glm::vec2 position;
glm::vec3 color;
};
```
- **Vertex Data Stored in a Buffer:**
```cpp
std::vector<Vertex> vertices = {
{{0.5f, -0.5f}, {1.0f, 0.0f, 0.0f}}, // Red Vertex
// ... other vertices ...
};
```
- **Buffer Creation and Memory Allocation:**
```cpp
vk::BufferCreateInfo buffer_info = { /* ... */ };
vertex_buffer = device.createBuffer(buffer_info);
vk::MemoryAllocateInfo alloc_info = { /* ... */ };
vertex_buffer_memory = device.allocateMemory(alloc_info);
```
- **Binding the Vertex Buffer:**
```cpp
cmd.bindVertexBuffers(0, vertex_buffer, offset);
```
**Benefits:**
- **Flexibility:** Easier to modify vertex data without changing shaders.
- **Performance:** Potentially better performance due to efficient memory usage.
- **Scalability:** Simplifies rendering more complex geometries.
## How the Sample Works
1. **Initialization:**
- **Instance Creation:** Initializes a Vulkan instance with Vulkan 1.3 API version and required extensions.
- **Device Selection:** Chooses a physical device that supports Vulkan 1.3 and required features.
- **Logical Device Creation:** Creates a logical device with enabled Vulkan 1.3 features like dynamic rendering, synchronization2, and extended dynamic state.
- **Surface and Swapchain Creation:** Sets up the window surface and initializes the swapchain for presenting images.
2. **Vertex Buffer Setup:**
- **Vertex Data Definition:** Defines vertices with positions and colors.
- **Buffer Creation:** Creates a buffer to store vertex data.
- **Memory Allocation:** Allocates memory for the buffer and maps the vertex data into it.
3. **Pipeline Setup:**
- **Shader Modules:** Loads and compiles vertex and fragment shaders.
- **Pipeline Layout:** Creates a pipeline layout (empty in this case as no descriptors are used).
- **Dynamic States Specification:** Specifies which states will be dynamic.
- **Graphics Pipeline Creation:** Creates the graphics pipeline with dynamic rendering info and dynamic states enabled.
4. **Rendering Loop:**
- **Acquire Swapchain Image:** Gets the next available image from the swapchain.
- **Command Buffer Recording:**
- **Begin Rendering:** Uses `vk::CommandBuffer::beginRendering()` with dynamic rendering info.
- **Set Dynamic States:** Sets viewport, scissor, cull mode, front face, and primitive topology dynamically.
- **Bind Pipeline and Vertex Buffer:** Binds the graphics pipeline and the vertex buffer.
- **Draw Call:** Issues a draw call to render the triangle.
- **End Rendering:** Uses `vk::CommandBuffer::endRendering()` to finish rendering.
- **Image Layout Transition:** Transitions the swapchain image layout for presentation using `vk::CommandBuffer::pipelineBarrier2()`.
- **Queue Submission:** Submits the command buffer to the graphics queue.
- **Present Image:** Presents the rendered image to the screen.
5. **Cleanup:**
- **Resource Destruction:** Cleans up Vulkan resources like pipelines, buffers, and swapchain images upon application exit.
## Dependencies and Requirements
- **Vulkan SDK 1.3 or Later:** Ensure you have the Vulkan SDK that supports Vulkan 1.3.
- **Hardware Support:** A GPU that supports Vulkan 1.3 features, including dynamic rendering, synchronization2, and extended dynamic state.
- **GLM Library:** Used for vector and matrix operations.
- **Shader Compiler:** GLSL shaders are compiled at runtime using a GLSL compiler.
