Caustica RTX

Caustica RTX is an experimental, RTX-focused fork of ComfyFluffy/Caustica 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

• Discord
• Modrinth
• CurseForge
• Gallery

Features

• Vulkan hardware path-traced world rendering
• DLSS Ray Reconstruction support
• DLSS Frame Generation and RTX 50 Multi Frame Generation up to 4x (experimental)
• NVIDIA Reflex with Low Latency Boost
• In-game DLSS, frame-generation, multiplier, Reflex, and menu-suspension controls
• PsychoV24 and analytical SDR tone mapping
• Shuffled-scrambled Sobol path and RIS sampling
• Correct alpha-tested redstone rendering
• HDR output
• Dynamic entity rendering in the ray-traced scene
• LabPBR-style material support
• OMM (Opacity Micro-Map) + SER (Shader Execution Reordering) optimizations

Requirements

• Vulkan graphics backend enabled
• Minecraft 26.2, Fabric Loader 0.19.3 or newer, Fabric API, and Java 25
• A GPU and driver with Vulkan ray tracing support
• NVIDIA RTX GPU and supported driver 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

Installation

1. Install Fabric Loader for Minecraft 26.2.
2. Install Fabric API.
3. Put the Caustica jar in your Minecraft mods folder.
4. Launch the game with the Vulkan graphics backend.
5. Open Video Settings to adjust Caustica RTX's renderer options.

Usage Notes

• Caustica is client-side only.
• DLSS Ray Reconstruction and Frame Generation require supported NVIDIA hardware and drivers.
• On Linux if Minecraft crashes on startup with stack overflow errors, try adding -Xss2M to the Java args to increase the stack size.
• Use Java args to improve performance. Minecraft Launcher default: -XX:+UseCompactObjectHeaders -XX:+AlwaysPreTouch -XX:+UseStringDeduplication -XX:+UseZGC
• Frame Generation, its 2x-4x multiplier, Reflex, and Reflex Boost are available in Video Settings.
• 3x and 4x Multi Frame Generation require a supported GeForce RTX 50 Series GPU and driver.
• 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