Minimal SDL3 GPU example

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Learning how to use new SDL3-GPU features with C++.

Project Setup

Uses CMake with presets and C++23 with std modules. Ninja is build tool.

• All the C++ code is in src folder.
  • .cppm files are C++ Module files.
  • main function is in main.cpp, this file also contains application state.
  • colors.cppm contains some static variables to print with ANSI colors to terminal
  • io.cppm contains file operations, reading shaders, and textures, as well as, making std::span from memory location.
  • sdl3-init.cppm contains logic to initialize SDL3 GPU.
  • sdl3-scene.cppm contains per-frame logic for drawing using SDL3 GPU API.
• Shaders, written in HLSL 6.4, are in shaders folder.
• Textures, in DDS format, are in textures folder.

External dependencies are managed via vcpkg. SDL3 is consumed as an dependency via vcpkg. .clang-tidy and .clang-format to maintain code formatting rules. .clangd to experiment with using clangd as lsp, it doesn't like modules.

Project uses CMakePresets json file to control platform some specific compiler configuration. As well as build (ninja) and external dependency (vcpkg) configuration.

Primary CMake file is in project root called CMakeLists.txt. There is only one of these.

Windows only for the moment, but it shouldn't have issues compiling on linux with some tweaks. e.g. adding Linux build presets.

Shader Compilation

CMake script uses a custom function to take list of shader source files and output compiled bytecode to bin/shaders directory. It also makes shader bytecode output a dependency of the application. So compilation error in shader will stop the build process.

As mentioned above, by default, code expects Windows. As it uses DirectX's DXC compiler to convert HLSL to DXIL bytecode. Application prefers DX12 over Vulkan. I suppose if the order were changed, it would need SPIR-V bytecode. Which would require changing shader complier from DirectX's DXC to Vulkan's DXC which is shipped with Vulkan SDK. Windows SDK's DXC cannot compile to SPIR-V, and Vulkan SDK's DXC cannot compile to DXIL. At least I wasn't able to make this work with versions I have installed on system.

Prerequisites

Build Tools

• CMake 3.31+
• vcpkg
• ninja 1.12+
• Windows SDK & MSVC build tools
• clang-tidy & clang-format

Depends on

Apart from prerequisite tools above, this project also depends on follow libraries; all loaded via vcpkg.

• SDL3: SDL 3.2, main focus of this repo.
• DDS-KTX: DDS/KTX image file loader via vcpkg project overlay functionality, as this library is not available in vcpkg repo.
• GLM: OpenGL Math Library, not just for OpenGL.

Configure and Build

In project root, from VS command prompt

# to configure the project
cmake --preset windows-default

# to build the project
cmake --build --preset windows-debug

# to clean the project outputs
cmake --build --preset windows-debug --target clean

Learning Progress

Each tag, modifies previous tag's sources.

• Clear Screen: Clear window with specified color.
• Basic Triangle: Draw a simple colored triangle. Press 1, 2, or 3, to change pipeline type, viewport, and scissor respectively
• Vertex Buffer Triangle: Draw a triangle using vertex buffer.
• Cull Modes: Draw triangle with Backface/Frontface Culling, Clockwise/Counter-Clockwise vertex ordering. Press 1-6 to toggle cull-mode + vertex-order combinations.
• Basic Stencil: Basic stencil operation. Substract mask from triangle.
• Index Buffer Shape: Draw a shape using Index Buffer.
• Instance Shapes: Slight tweak of previous, simple change to vertex shader and increase instance count in cpp.
• Basic Texture: Load a texture with mipmaps and use it with previous. Change Sampler type with key 1-6.
• Instanced Cubes with depth testing: Draw multiple textured cubes with perspective projection, with depth buffer testing.

At this point code is refactored to move some of basic complexity out, per project setup block above.

• Refactored Code: Same visually as before, but code is refactored into multiple files.
• Shader Grid: Draw a grid using shaders.

References

• https://github.com/TheSpydog/SDL_gpu_examples : my code is basically following this repo as example/source. But without "framework" portion so I can understand it better.
• https://asliceofrendering.com/scene%20helper/2020/01/05/InfiniteGrid/ : Grid shader article.