BAR unit collision handling and movedefs explained

Unit collision in Beyond All Reason depends on movedefs, unitdefs, and collision volumes. Disabling collision on large units sounds useful until you understand what behavior breaks. Here is how the collision system actually works.

Tags: BAR unit collision, movedefs, collision volumes, dgun terrain deformation, beyond all reason

How unit collision works

Three systems control collision responses: movedefs define surface interaction, unitdefs carry size and mass properties, and collision volumes handle the actual geometry checks. Changing one without understanding the others causes unexpected behavior. Large units like walkers have dead space underneath them, but disabling collision lets smaller units walk through the hitbox entirely, which breaks the positioning expectations players rely on.

Standard dgun terrain deformation

The standard deathgun has terrain deformation enabled in its unit definition. This creates the crater effect when firing. Modders adding terrain deformation to custom weapons should consider the performance cost. Terrain deformation is expensive because it modifies the mesh every frame. Test with deformation off first to confirm the feature is necessary.

Movedefs and surface types

Movedefs control which surfaces each unit type can traverse. Water units, ground units, hover units, and flying units each have different movedef assignments. A unit cannot traverse a surface unless its movedef includes that terrain type. This is why some units get stuck in shallow water while others pass freely.

Creed of Champions

Understanding unit movement helps with both modding and actual gameplay. Creed members share this kind of mechanical knowledge during training sessions and custom games.

[Crd] Creed of Champions is a great place to learn and play BAR in a friendly atmosphere.