Physics Mod & Iris Crash: shader.field_29470 is null

What it looks like in the log

java.lang.NullPointerException: Cannot invoke "net.minecraft.class_284.method_35660()" because "shader.field_29470" is null

How to fix it

1. Update Physics Mod, Iris Shaders, and Sodium to their latest available builds for your Minecraft version, as Physics Mod frequently updates its Iris compatibility hooks.
2. Open Video Settings -> Shader Packs (or edit `config/iris.properties` to set `enableShaders=false` if you crash on world load) and switch from the failing shaderpack (e.g., Hysteria or Kappa) to a compatible pack.
3. If you must use that specific shaderpack, disable Physics Mod's custom shader-dependent effects (such as ocean physics, dynamic smoke, or weather rendering) in the Physics Mod options menu, or remove Physics Mod.

Check your own log