OpenDLSS-NR

A Vulkan reimplementation of NVIDIA's DLSS 5 Neural Rendering network, bit-exact against the original.

The same 71-block Swin / ViT network as DLSS-NR build 310.8.0, running FP8 on the tensor cores. The intermediates match too, not just the final image: all 75 block boundaries, byte for byte.

ports/browser-webgpu/ is a second, independent implementation: the same bytes in a browser, with no tensor cores and no FP8.

You supply the weights, as a model directory in the layout described below.

The network

A U-net of shifted-window transformer blocks with a global ViT at the bottom: 71 blocks over six pooling levels, FP8 (E4M3) activations with FP16 accumulation, 141 MiB of weights. It is a generative neural rendering network (NVIDIA's term): it re-renders the frame the engine already drew, generating detail from injected noise and adjusting tone, structure and skin under a style setting. Input and output are the same resolution; it is not an upscaler.

The WebGPU port at 2048x1152, NR off on the left and on on the right. Scene: Cowboy Gramps by Muhammed Ismayil, CC0.

It takes one rendered frame (a low dynamic range proxy of it, three lanes of Gaussian noise, the previous frame's output reprojected, and five conditioning scalars) and produces four f32 channels per pixel: an RGB residual and one temporal-blend logit. docs/network.md is the graph in full. NVIDIA describes the model in its report, DLSS 5: Generative Neural Rendering (project page).

Build and run

powershell -File scripts\fetch_tools.ps1 [-Npm]     # once: tools\ (glslang, Vulkan-Headers, volk, CMake, Ninja)
powershell -File scripts\build.ps1                  # shaders, PTX, build\dlss5vk.exe
powershell -File scripts\fetch_filament.ps1         # once, for the demo: third_party\filament (+ the patch)
powershell -File scripts\build_filament.ps1         # once, for the demo: third_party\filament-install
powershell -File scripts\build_demo.ps1             # build\demo\dlss5-demo.exe

build\dlss5vk.exe bench   --model <dir> --width 768 --height 768
build\dlss5vk.exe profile --model <dir> --width 768 --height 768   # per-dispatch timings
build\dlss5vk.exe parity  --model <dir> --fixture <dir>            # bit-exactness against a fixture
build\dlss5vk.exe verify  --model <dir> --fixture <dir>            # block-0 kernel-by-kernel bisect
python scripts\ptx\test_fast_divmod.py                             # the PTX divider, over every n < 2^24 (numpy)

The demo can be double-clicked. It lists every scene under build\scenes in the Demo scene dropdown and starts on the first one, or loads the glTF given on the command line. The model directory is --model <dir>, else DLSS5VK_MODEL, else models\nr next to this README. See demo/README.md for the renderer, the keys, the scenes and view.json.

Performance

RTX 4070 SUPER, whole network per frame, minimum over 40 frames. 241 dispatches at every resolution.

The GPU alternates between two clock states under sustained load, so medians run a few percent higher. Compare minima.

What is here

Not implemented: DLSS-SR, which is a different network. The temporal path is implemented, but in the demo: the network's history input lanes and its per-pixel blend logit drive a reprojected feedback loop (docs/frame.md). The dlss5vk tool runs single frames with no history, which is what the reference captures were made with.

Requirements

• Windows, an NVIDIA Ada (or newer) GPU and a driver exposing VK_KHR_cooperative_matrix, VK_NV_cooperative_matrix2, VK_EXT_shader_float8 and VK_NV_cuda_kernel_launch.
• Visual Studio 2022 or later with the C++ x64 toolset (any edition or the Build Tools; found through vswhere, or set VCVARS64 to your vcvars64.bat), git, Python 3 for the PTX generators, and Node.js + npm and Pillow for the scene converter.
• The portable toolchain under tools/ (git-ignored): scripts\fetch_tools.ps1 downloads glslang 16.6.0, Vulkan-Headers v1.4.363, volk (pinned tags), CMake 3.31 and Ninja 1.13. No Vulkan SDK install is needed. -Npm also installs the scene converter's modules into tools\gltf.
• For the demo: Filament v1.77.0, cloned and patched by scripts\fetch_filament.ps1 and built once by scripts\build_filament.ps1 (both git-ignored; about 15 minutes and 6 GB of build tree, placed in %LOCALAPPDATA%\dlss5-vulkan or DLSS5_FILAMENT_BUILD_DIR; DLSS5_BUILD_JOBS caps the parallel compiles, default 8, because MSVC takes up to a GB per job on Filament).

Model directory

nr::Model reads manifest.json: a stages array (each entry: id, file relative to the directory, packedByteLength, sha256) and a tensors array (each entry: name, block, layer, parameter, stage, stageOffset, byteLength). Stage files hold the E4M3 weights as packed bytes; the host re-lays them out into the matrix forms the kernels consume (src/nr_model.cpp). Nothing in this repository produces such a directory.

The graph is the 71-block network of 310.8.0 and nothing else: a model with a different block count is refused at load.

Fixtures

parity compares against recorded captures of the original, which are not part of this repository. A fixture is a directory with a manifest.json:

Everything is validated before the GPU runs, and a fixture that fails any of it is refused: a declared check without its reference, a reference that is missing, short or names nothing in the graph, a reference no declared check uses, or a comparable boundary (blocks 0-69, the five encoder transitions) with neither a reference nor a reason. Verdicts are bit-exact (the pass), equal only up to the sign of zero (a failure), within one code (the 8-bit capture only, reported apart) or a mismatch; see docs/numerics.md. The head and the output are compared on the production schedule, resubmitted --repeat times (default 3), which must also agree with the same graph under barriers; the boundaries come from an instrumented run, whose head must agree with production's. verify additionally needs inputFeatures and a block-0 reference.

Tuning switches

All default to the fast, exact route. Every switch keeps the output byte-identical, and parity under each of them is part of the gate. Any switch that sends a kernel back to GLSL also turns counter chaining off, because only the PTX kernels take part in it.

• DLSS5VK_UNFUSED=1 runs the GLSL reference route, up to 2560x1440: it materializes every intermediate.
• DLSS5VK_PTX_DIR is the PTX directory, default build/ptx.
• DLSS5VK_CHAIN=0 puts barriers between every launch instead of counter chaining.
• DLSS5VK_PTX_GEMM, GEMMT, GEMMV, BLOCK32, FFN, QKV and ATTN set to 0 take one kernel family back to its GLSL spelling.
• DLSS5VK_ATTN_STREAM forces streamed global attention off (0) or on (1).
• DLSS5VK_SPLITK=0, DLSS5VK_VIT_CHAIN=0 and DLSS5VK_NO_PTX_MLP=1 disable split-K, the ViT chain and the PTX MLP.
• DLSS5VK_NO_FUSE_PRE, POOL, UPRES and POST set to 1 drop one fusion each.
• DLSS5VK_CHAIN_MASK is a bit mask: 1 expert stages, 2 c32 blocks, 4 split GEMMs. Default 3.
• DLSS5VK_DEFER_MAX is the widest stage whose projection GEMM is fused. Default 128.
• DLSS5VK_VALIDATION=1 runs under the Khronos validation layer (refused if it is not installed: a Vulkan SDK, or VK_LAYER_PATH at a build of Vulkan-ValidationLayers); an error it reports fails the run. DLSS5VK_DEBUG=1 only prints the driver's own messages (the PTX compiler's among them). DLSS5VK_LIST_EXTENSIONS=1 lists extensions.

Documentation

docs/README.md is the index: network.md is the graph, numerics.md the exactness contract, weights.md the layouts, execution.md the scheduling, and frame.md the demo's frame.

Not affiliated with NVIDIA

This project is not affiliated with, endorsed by, or supported by NVIDIA. It contains no NVIDIA software, weights, headers, or instructions for obtaining them. No rights under any NVIDIA intellectual property are granted or implied by this repository or its license, and you are responsible for the licenses that apply to whatever model data you use with it.

License

MIT for everything in this repository (LICENSE). Third-party components are listed in NOTICE.