[Immersive Vehicle/IV/MTS] Better Collisions

IV Better Collisions

  The Problem

  If you've ever used Immersive Vehicles (MTS), you know the pain: vehicles clip through walls, get
  stuck inside blocks, and break pathfinding. Once a vehicle is lodged in a wall, there's often no way
   to get it out without creative mode or commands.

  MTS has its own collision system, but it can fail in certain edge cases - high speeds, tight angles,
   or specific block shapes. When it does, vehicles phase right through solid blocks.

  The Solution

  IV Better Collisions acts as a post-tick safety net. After MTS has done its own collision checks
  each game tick, this addon scans every vehicle's collision boxes against the world's solid blocks.
  If any overlap is detected, the vehicle is pushed out using the Minimum Translation Vector (MTV)
  algorithm.

  The result: vehicles slide along walls instead of going through them, just like you'd expect from a
  real vehicle hitting a surface at an angle.

  How It Works

  - Wall Sliding: When a vehicle hits a wall at an angle, only the motion component going into the
  wall is cancelled. The tangential motion is preserved, creating a natural sliding effect along the
  surface.
  - Per-Axis Correction: The addon calculates penetration depth on X and Z axes independently and
  pushes the vehicle out on whichever axis has the smallest overlap. This produces realistic
  deflection.
  - Ground Device Compatible: Y-axis (vertical) collisions are intentionally left to MTS's ground
  device system. This addon only handles horizontal wall collisions - it won't interfere with wheels,
  suspension, or terrain following.
  - Safety Thresholds: Corrections are capped at 0.9 blocks to avoid teleporting vehicles that were
  legitimately placed inside terrain. Newly spawned vehicles are also given a grace period (2 seconds)
   so MTS's own placement logic isn't disrupted.

  Features

  - Zero configuration - drop the jar in your mods folder and it works
  - Server-side only - no client installation needed (works on both sides too)
  - Lightweight - only processes vehicles with active block collision boxes
  - Non-destructive - doesn't modify MTS code; uses reflection to read vehicle state
  - Compatible - works with all MTS/IV vehicle packs (cars, trucks, planes on ground, etc.)

  Installation

  1. Requires Forge 1.20.1 (47.x)
  2. Requires Immersive Vehicles (MTS) 22.0.0+
  3. Drop IVBetterCollisions-1.0.0.jar into your mods/ folder
  4. Done. No config files, no setup.

  Technical Details

  The addon hooks into Forge's LevelTickEvent at the END phase, after all entities (including MTS
  vehicles) have completed their tick updates. For each vehicle:

  1. Reads the vehicle's block collision boxes (the red debug boxes in MTS)
  2. Checks each box against surrounding solid blocks using Minecraft's VoxelShape system
  3. Computes the MTV (smallest push direction) on horizontal axes
  4. Applies position correction and zeroes out the blocked motion component
  5. Updates collision box positions for consistency

  All MTS internals are accessed via cached reflection - no compile-time dependency, no mixins, no
  access transformers.

  FAQ

  Q: Does this work with [vehicle pack name]?
  A: Yes. It works with all vehicle packs because it uses MTS's own collision box definitions (the
  ones marked as BLOCK collision type in the vehicle JSON).

  Q: Will this affect performance?
  A: Minimal impact. The addon only iterates blocks within each collision box's bounds - typically
  just a few blocks per vehicle. Reflection fields are cached at startup.

  Q: Does this fix vehicles getting stuck in walls that are already there?
  A: It will push vehicles out if the penetration is less than 0.9 blocks. Vehicles deeply embedded in
   terrain (e.g., from world edits) won't be affected to avoid unintended teleportation.

  Q: Server-side only?
  A: The collision logic runs server-side. Position corrections are synced to clients via MTS's
  existing rubberbanding system. You can install it on both sides safely.

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