Boolean-breakable trees technology is a dynamic procedural breaking method that allows you to break trees precisely at the impact point. It subtracts a Boolean cut mesh from the main mesh (both render and physics) at the impact point.
This separates the tree parts that are cut as a result (the cut shape is generally expected to be large enough to be able to cut through the trunk in a single operation). Non-breakable tree pieces, like patches of foliage, are then assigned to the broken parts and have their touch-bending activated if they have it set up.
Pic01: Boolean breakage in action (with p_draw_helpers = 1 active)
The boolean cutter meshes are defined within the physics.lua file found in:
<Your_Project>\
Scripts\physics.lua
Within this file you define the geometry and params on how you want the cut to happen when requested by the system.
Boolean breakability is activated via surface type scripts and can be applied to any physicalized object that has a Boolean-friendly physicalized render mesh (i.e. its physics proxy is also the render mesh).
Example surface type (mat_wood_breakable), with boolean breakage params active:
<Your_Project>\
Libs\MaterialEffects\Surfacetype.xml
<SurfaceType name="mat_wood_breakable" type="wood">
<Physics friction="0.5" elasticity="0.05" breakable_id="2" pierceability="7" break_energy="7000" hole_size="1.4" hit_points="10" hit_radius="0.4" hit_maxdmg="10" can_shatter="1" sound_obstruction="0.5" />
<BreakageParticles type="joint_break" effect="breakable_objects.tree_break.small" />
<BreakageParticles type="joint_shatter" effect="breakable_objects.tree_break.small" />
<BreakageParticles type="destroy" effect="breakable_objects.tree_break.small" count_per_unit="1" count_scale="1" scale="1" />
<AI fImpactRadius="2.5" fImpactSoundRadius="30" fFootStepRadius="20" proneMult="0.2" crouchMult="0.5" movingMult="2.5" />
</SurfaceType>
Trees, however, can do some additional processing, such as
Pic03: Auto generated capsule at the end of the broken trunk part.
Depending on the DCC tool used - the links below show you how to setup vegetation assets for breaking.