Slipstream Viewer

A third-party viewer for Second Life, built around a GPU-driven Vulkan renderer. Slipstream began as a fork of Alchemy Viewer (itself built on Linden Lab's viewer) and is now developed independently: the render pipeline has been rewritten from scratch, and features from other open source viewers, plus our own, are folded in.

This software is not provided or supported by Linden Lab, the makers of Second Life.

Status: beta. Linux x86_64 and Windows x64. Please report problems on the issue tracker.

• Website and downloads: https://slipstreamviewer.org
• Help wiki: https://slipstreamviewer.org/wiki/
• Privacy policy: https://slipstreamviewer.org/privacy.html (we collect no data)

Why

Second Life viewers traditionally render the way they did in 2007: the CPU walks the scene every frame, binds state and issues draw calls one face at a time. In busy places (clubs, crowds, mainland) the CPU becomes the bottleneck long before the GPU does. Slipstream moves that work onto the GPU.

On an RTX 5090, a busy scene that runs around 24 FPS in a conventional GL-based viewer runs around 90 FPS here; quieter scenes hit the monitor's refresh rate. Numbers vary a lot by scene and hardware; these are indicative, not a benchmark.

The render engine

The Vulkan renderer owns the scene on the GPU. The CPU's per-frame job shrinks to streaming changes and dispatching a handful of compute and indirect draws.

• Persistent GPU scene. Every visible face lives in a persistent instance buffer (transform, material, bounds, flags) and a shared vertex/index buffer. Objects are uploaded when they change, not every frame.
• Bindless materials and textures. One large descriptor table holds every resident texture, and materials index into it. There are no per-draw binds.
• Compute culling + multi-draw indirect. A compute pass does frustum culling, LOD selection and bucket sorting (opaque, alpha-mask, alpha-blend, rigged, …) and writes indirect draw commands. The whole world draws in a few vkCmdDrawIndexedIndirectCount calls.
• Depth pre-pass. A depth-only pass over the same indirect draws, then the lit pass with depth-equal tests, so every pixel is shaded exactly once.
• Clustered local lighting. Point lights and projectors are culled into screen-space clusters.
• GPU skinning and animation. Skin palettes and other avatars' animation are evaluated on the GPU, with a pre-skin compute pass feeding the rigged draws. Flexible prims are skinned on the GPU too.
• Streaming that follows visibility. Texture residency and quality follow what the GPU culler actually sees, with async uploads, a staging ring and a VRAM budget.
• Modern post-processing. HDR with seven tone mappers, bloom, SSR, reflection probes, planar mirrors, SSAO / GTAO ambient occlusion, depth of field, and FXAA / SMAA / TAA with temporal upscaling.

The legacy OpenGL pipeline has been removed.

Highlights

• Hardware ray tracing (RTX 20-series / RX 6000 and newer): ray-traced sun, moon and projector shadows with adjustable softness. They're exact, don't leak through walls, and keep up with moving stage lights.
• Shadow maps done properly: cascaded sun shadows with Gaussian or contact-hardening (PCSS) filtering, and a large, cached projector-shadow budget.
• Photo Studio: colour grading, curves, scopes, tone mapping, depth of field, sky effects.
• Third-person shooter camera (Preferences → Move & View), pie menus, live font switching with Add Font…, sim-wide @mentions, snapshot presets up to 10240 × 4320, and Import from Another Viewer for your old settings.

See the features page for the full list.

Requirements

• Linux: x86_64, glibc 2.38 or newer, an x86-64-v2 CPU.
• Windows: Windows 10 or 11, x64.
• GPU: a Vulkan 1.3 driver: NVIDIA GTX 750 / 900 series or newer, AMD RX 400 series or newer (any GCN Radeon on Linux), or Intel HD/UHD 500 / 600 series or newer.
• Ray-traced features need VK_KHR_ray_query (NVIDIA RTX 20-series+, AMD RX 6000+). Without it, everything else still works.

Download

Builds are published on the website and as releases, each with a SHA-256 checksum.

• Windows: run Slipstream_<version>_Setup.exe (per-user install, no admin prompt), or unzip Slipstream_<version>_win64.zip and run SlipstreamViewer.exe.
• Linux: unpack Slipstream_<version>_x86_64.tar.xz and run ./slipstream.

Building

Slipstream builds on Linux; the Windows version is cross-compiled from Linux with clang-cl and xwin.

make            # venv + dependencies + configure + build + package
make run        # launch the packaged viewer
make windows    # cross-build the Windows x64 package
make help       # every target and override

The first build downloads about 1 GB of prebuilt third-party libraries. Package lists and the Windows toolchain setup are on the wiki's building page.

Credits and license

Slipstream is built on Linden Lab's Second Life viewer and the work of the Alchemy Viewer project, and includes RLVa. Some features are ported from other open source viewers:

• Firestorm Viewer (The Phoenix Firestorm Project, Inc. and contributors, including Ansariel Hiller, Cinder Roxley and Techwolf Lupindo): area search, teleport history, LSL preprocessor, virtual trackpad, pie menus, the Contacts window. The LSL preprocessor is Copyright (c) 2010 Modular Systems (BSD license; see indra/newview/licenses-*.txt).
• Black Dragon Viewer by NiranV Dean: camera tools, camera recording and playback, bone camera and head tracking, depth of field focus modes, right-click-drag orbit.

Original copyright headers are kept in the ported files. Source is licensed under the LGPL 2.1; see doc/LICENSE-source.txt and doc/LGPL-license.txt. Second Life and related marks belong to Linden Research, Inc. Slipstream is not affiliated with or endorsed by Linden Lab.