Caustica

Caustica is a ray-traced renderer for Minecraft 26.2's Vulkan backend. It replaces the vanilla world view with hardware ray tracing and NVIDIA DLSS features while keeping Minecraft's familiar UI and gameplay intact.

Caustica is early software. Expect bugs, missing visual cases, and frequent changes while the renderer is being built.

Links

• Upstream project
• Discord
• Upstream Modrinth releases
• Upstream CurseForge releases
• Gallery

Features

• Vulkan hardware path-traced world rendering
• DLSS Ray Reconstruction support
• Streamline DLSS Frame Generation and Multi Frame Generation support
• HDR output
• Dynamic entity rendering in the ray-traced scene
• LabPBR-style material support
• OMM (Opacity Micro-Map) + SER (Shader Execution Reordering) optimizations

Fork Improvements

This fork adds an energy-preserving EON rough-diffuse BRDF, corrected Kulla-Conty GGX multiscattering, linear-light material ingestion, and selectable SDR/HDR tone mapping with a shared PsychoV implementation. HDR and SDR retain separate output gamut and transfer handling while sharing the same traced scene radiance.

Requirements

• Minecraft 26.2, Fabric Loader 0.19.3 or newer, and Fabric API
• Java 25 with a larger main-thread stack (-Xss16m recommended)
• Vulkan graphics backend enabled
• A GPU and driver with Vulkan ray tracing support
• Windows 10 RS3 64-bit or newer for the bundled Streamline 2.12 runtime
• Current NVIDIA driver and a supported GeForce RTX GPU for DLSS features
• HDR-capable display and OS HDR mode for HDR output
• On Linux, an HDR-capable Wayland compositor and a native Wayland session for HDR output
• Install LabPBR resource pack like SPBR for better visuals

The current production JAR bundles Streamline for Windows x64. Ray Reconstruction is available on GeForce RTX GPUs when the driver reports support. Frame Generation requires GeForce RTX 40 or 50 Series; Multi Frame Generation above 2x requires a supported GeForce RTX 50 Series GPU.

Installation

1. Install Fabric Loader for Minecraft 26.2.
2. Install Fabric API.
3. Put the Caustica jar in your Minecraft mods folder.
4. Select Java 25 and add -Xss16m to the instance's Java arguments. Adding --enable-native-access=ALL-UNNAMED is recommended for Java's native-access API.
5. Launch the game with the Vulkan graphics backend.
6. Open Video Settings to adjust Caustica's renderer options.

Do not download or install Streamline separately. The production JAR contains the required signed Streamline 2.12 plugins and extracts them into minecraft/caustica-streamline/natives on first launch. The NVIDIA binaries remain separately licensed and are not covered by Caustica's LGPL license; see the distribution notice and third-party notices.

Using DLSS

Ray Reconstruction

Open Options → Video Settings → Ray Tracing and enable DLSS Ray Reconstruction. Select the desired DLSS Quality mode next to it. Ray Reconstruction is enabled by default; when it is off or unavailable, Caustica traces at native output resolution.

Frame Generation and Multi Frame Generation

Open Options → Video Settings → Ray Tracing → DLSS Frame Generation:

1. Set Frame Generation Mode to Fixed.
2. Select the desired multiplier. 2x generates one frame; higher multipliers require GPU support.
3. Leave UI Recomposition and Menu Suspension enabled for normal play.
4. Use NVIDIA Reflex: On or On + Boost. Frame Generation forces effective Reflex On.
5. Enable VSync for tear-free MAILBOX presentation, or disable it for uncapped IMMEDIATE presentation.
6. Close the screen so Minecraft can recreate the swapchain when required.

If MAILBOX presentation is unavailable, Caustica fails closed to ordinary FIFO VSync without Frame Generation. Dynamic MFG is not available in Caustica's Vulkan renderer; all exposed multipliers are fixed.

Usage Notes

• Caustica is client-side only.
• DLSS Ray Reconstruction and Frame Generation require supported NVIDIA hardware and drivers.
• If Minecraft crashes during NVIDIA initialization, confirm Java 25 and -Xss16m are active.
• Use Java args to improve performance. Minecraft Launcher default: -XX:+UseCompactObjectHeaders -XX:+AlwaysPreTouch -XX:+UseStringDeduplication -XX:+UseZGC
• Advanced Streamline counters and the VRAM estimate are available from the Frame Generation screen's Advanced Diagnostics page.
• HDR output requires an HDR swapchain and a correctly configured HDR display.
• When HDR is enabled on Linux, Caustica selects GLFW's native Wayland backend automatically. X11/XWayland surfaces generally do not expose the required HDR10/PQ format.
• If Minecraft falls back to OpenGL after a crash, re-enable the Vulkan backend before using Caustica again.

Compatibility

Caustica takes over the world renderer, so other mods that heavily modify world rendering, shader pipelines, post-processing, or the Vulkan backend may conflict. UI-only mods are more likely to work.

Status

Caustica is not a finished renderer yet. Current work focuses on visual correctness, world coverage, stability, and making the SDR/HDR presentation paths behave consistently.

License

Caustica's project-owned source code and documentation are licensed under the GNU Lesser General Public License v3.0 or later. See LICENSE.md, COPYING, and COPYING.LESSER.

Release artifacts may bundle NVIDIA DLSS/NGX SDK components under NVIDIA's own license terms. See THIRD_PARTY_NOTICES.md.

TODO List

• Nether/End sky, weather, volumetric fog/clouds
• NRD + FSR for non-NVIDIA GPUs
• LOD
• ReSTIR