Sascha Willems' Vulkan Samples — Ported to Flax

Credits to Sascha Willems for writing the original Vulkan samples. This repository ports a selection of them to the Flax Engine while keeping the original rendering logic (camera math, GLSL-equivalent shaders, glTF scenes) intact.

A collection of classic real-time rendering samples — a spinning triangle, animated gears, omni/directional shadow mapping, and hardware ray-traced shadows — rebuilt as standalone Flax projects.

Objective

• Learn the Flax graphics abstraction layer by porting well-understood samples to it.
• Build tech demos that auto-port across backends — the same code targets DirectX 11, DirectX 12, Vulkan, and WebGPU.
• Feed the lessons back into the engine — use the experience gained here to potentially extend or modify the full Flax renderer.

Sample Compatibility

Every sample targets Flax 1.13. Some need a small engine patch applied on top of 1.13. The patches ship inside FlaxPatches.zip in this repository — see Applying a Patch.

Sample	Patch required	What it shows
triangle	—	Minimal "hello triangle"
gears	—	Animated mechanical gears
shadowmapping	—	Directional/spot shadow maps
shadowmappingomni	—	Omni-directional (point light) cube shadow maps
texture	KTX.diff	KTX texture loading
parallaxmapping	KTX.diff	Parallax-occlusion mapping
shadowmappingAddRT	HWRT_D3D12_VK.diff	Hardware ray-traced shadows (directional)
shadowmappingomniAddRT	HWRT_D3D12_VK.diff	Hardware ray-traced omni shadows

• No patch → runs on a stock Flax 1.13 build.
• KTX.diff → adds KTX texture support: texture, parallaxmapping.
• HWRT_D3D12_VK.diff → adds hardware ray tracing on DirectX 12 and Vulkan: shadowmappingAddRT, shadowmappingomniAddRT. Running these on Vulkan also needs a SPIR-V-enabled DXC — see Ray Tracing on Vulkan: SPIR-V Shader Compiler.

Requirements

• Windows x64
• Flax Engine 1.13 (built from source — see below)
• For the ray tracing samples: a GPU + driver supporting DirectX 12 or Vulkan hardware ray tracing
• For the ray tracing samples on Vulkan: a SPIR-V-enabled DirectX Shader Compiler (see Ray Tracing on Vulkan: SPIR-V Shader Compiler)

Getting Flax 1.13

Clone the engine and check out the 1.13 branch (the -b 1.13 flag is required to get the right branch):

git clone -b 1.13 https://github.com/FlaxEngine/FlaxEngine.git

Applying a Patch

Some samples require an engine patch. The patches are distributed as FlaxPatches.zip in this repository, which contains KTX.diff and HWRT_D3D12_VK.diff.

Why a zip? A .diff is byte-sensitive — Git apply fails if even the line endings change. When raw .diff files are committed to GitHub, Git's automatic line-ending normalization (and, for some files, LFS handling) rewrites them on checkout, so the copy you clone no longer matches the original and git apply rejects it. Packing them inside FlaxPatches.zip keeps the bytes exactly as authored, so the extracted files apply cleanly. Unzip FlaxPatches.zip first — don't try to use any loose .diff from the repo tree.

Important: these .diff files patch the FlaxEngine repository (branch 1.13) — not this samples repository. Apply them inside your cloned engine source tree, then rebuild the engine.

Extract FlaxPatches.zip, copy the .diff you need into the root of your Flax 1.13 engine clone (or reference it by full path), apply it there, then rebuild the engine:

# 1. Unzip FlaxPatches.zip to get KTX.diff and HWRT_D3D12_VK.diff.
# 2. Run these from inside your FlaxEngine clone (the 1.13 branch), NOT from the samples repo.

# KTX texture support — needed for: texture, parallaxmapping
git apply KTX.diff

# Hardware ray tracing (DirectX 12 / Vulkan) — needed for: shadowmappingAddRT, shadowmappingomniAddRT
git apply HWRT_D3D12_VK.diff

Apply only the patch(es) for the sample(s) you intend to run. The patches are independent.

Ray Tracing on Vulkan: SPIR-V Shader Compiler

Only needed for the ray tracing samples (shadowmappingAddRT, shadowmappingomniAddRT) when running on Vulkan. DirectX 12 works without this step.

The ray tracing samples compile their inline ray-query shaders with the DirectX Shader Compiler (DXC). On Vulkan these shaders must be emitted as SPIR-V, but the dxcompiler.dll that ships with the Windows SDK is built without SPIR-V code generation. Using it produces:

Failed to compile 'Shadowmapping'. SPIR-V CodeGen not available. Please recompile with -DENABLE_SPIRV_CODEGEN=ON.

To fix this, swap in a SPIR-V-enabled build of DXC:

1. Download the latest release from the official DirectX Shader Compiler releases.
2. From the downloaded package, open bin/x64.
3. Copy dxcompiler.dll and dxil.dll into your engine's third-party binaries folder:

FlaxEngine\Source\Platforms\Windows\Binaries\ThirdParty\x64

Overwrite the existing files, then rebuild/relaunch the editor. DirectX 12 ray tracing is unaffected by this swap.

Running a Sample

1. Build the Flax Editor from your 1.13 engine source.
2. Open the sample as a project in the Flax Editor (open its *.flaxproj).
3. In the Content Browser, search for Main and open the Main scene.
4. Press Play in the editor.

You can also cook the project to produce a standalone build.

Debugging the Ray Tracing Samples

The ray tracing demos (shadowmappingAddRT, shadowmappingomniAddRT) can only be GPU-debugged with NVIDIA Nsight Graphics. They will not work in RenderDoc.