Soft zones

A body is not equally stiff everywhere. A front crumple zone should fold, and a cabin should keep its shape. A stiffness zone says where. It is a box on the body that divides the dent of every hit that lands inside it. The zones live in the dent profile, and the Zone Editor draws and shapes them in the Blueprint editor. Zones divide dents, not paint: the paint wears as the metal moves, whatever the zone.

What it does

Each zone is a box. A hit inside it pushes the metal less, or more, than the rest of the body. A stiffer zone also holds a sill or a roof rail in place while the door between two of them caves in. A crush press ignores zones.

The Zone Editor in the Blueprint viewport, with three zones added to the body for this shot.

How it works

• The box. The box is in the root component’s space, in cm. Outside it, the zone changes nothing. A face on the body’s collision, or past it, counts as the skin: the zone holds full strength up to it. Part of the box past the lattice is ignored.
• Stiffness. At 1 the zone dents like the rest of the body. At 3 a hit dents a third as deep. At 0.5 it dents twice as deep. Higher is stiffer, so higher is shallower.
• Edge Width. The zone fades in over a band along its inner faces, so two zones that run into each other blend. Two zones that only touch both fade out at the shared face.
• Max Depth. The deepest any hit pushes the body inside the box, however many hits come. 0 uses the profile’s Max Displacement.
• Mirrored. The zone also applies reflected across the body’s centre line, so one zone covers a left and a right door.
• Overlap. Where boxes overlap, the stiffer one wins.

The Zone Editor draws each zone as the game paints it. H cycles the lattice heatmap: off, around the selected zone, or every node. The editor’s hint line lists the rest: LMB selects, RMB opens the menu, Ctrl+D duplicates, Del deletes, M mirrors, F focuses and Esc deselects.

The editor draws and edits zones only in the Blueprint editor’s viewport, for a selected deform or vehicle adapter component. A level and Play In Editor show nothing. Presets for the menu come from Project Settings > Plugins > Crushform Zone Editor.

Set it up

1. Make the profile as in Dents and the lattice, steps 1 and 2. On a vehicle, set the adapter’s Deform Profile and keep Dirt and Dents on. With Deform Profile empty, the vehicle uses the project’s default profile, and the editor has nothing of its own to edit. The plugin’s sedan profile, DA_CF_Profile_Sedan, ships with no zones, so the zones below are the ones you add.
2. Open the vehicle’s Blueprint and select the adapter component in the viewport or in the Components list.
3. In the Details panel, find the Stiffness Zones section and click Add Zone. The new zone sits in the middle of the lattice, a quarter of its size.
4. Drag the zone’s faces in the viewport until its box covers the part you want to stiffen or soften. Set Stiffness, Edge Width and Max Depth on the zone’s card or in its row.

Stiffness Zones
DA_CF_Profile_Sedan · used by 1 asset	Add Zone
Stiffness Zones	2 Array elements
Index [ 0 ]	Neutral
Index [ 1 ]	Cabin
Box
Stiffness	2.0
Edge Width	20.0
Max Depth	12.0
Mirrored
Name	Cabin

The Stiffness Zones group of a dent profile, with one zone expanded.

5. For a part that comes in pairs, such as the doors, choose Mirror Left and Right from the menu. The zone then covers its reflection across the centre line too.
6. Save the profile asset. Every edit goes to the profile, and every asset that uses the profile gets the same zones.

Plugins - Crushform Zone Editor

The stiffness zone editor's presets: Project Settings > Plugins > Crushform Zone Editor, kept in DefaultEditor.ini for the team.

Zones
Zone Presets	4 Array elements
Index [ 0 ]	Frame
Name	Frame
Stiffness	3.0
Max Depth	0.0
Edge Width	20.0
Index [ 1 ]	Cabin
Name	Cabin
Stiffness	2.0
Max Depth	12.0
Edge Width	20.0
Index [ 2 ]	Crumple
Name	Crumple
Stiffness	0.5
Max Depth	0.0
Edge Width	20.0
Index [ 3 ]	Neutral
Name	Neutral
Stiffness	1.0
Max Depth	0.0
Edge Width	20.0

The zone presets in Project Settings, under Plugins > Crushform Zone Editor.

Use it

No Blueprint or C++ call changes zones at run time. Zones are data in the profile. The only C++ helper is FCFStiffnessZone::MirrorBox, which gives the box of a zone’s reflected twin:

// The twin of a mirrored zone: its box reflected across Y = 0 of the root component's space.
const FBox Twin = FCFStiffnessZone::MirrorBox(Zone.Box);

Zone is an FCFStiffnessZone from the profile’s UCFProfile::StiffnessZones.

Key settings

Property	What it does	Default
UCFProfile::StiffnessZones	The zones of the profile, shown as Stiffness Zones.	Empty
FCFStiffnessZone::Box	The zone’s box, root component space, cm.	Invalid until set
FCFStiffnessZone::Stiffness	Hits push this much less here: 1 is the body, higher is stiffer.	1
FCFStiffnessZone::EdgeWidth	Width, cm, of the band along the inner faces where the zone fades in.	20
FCFStiffnessZone::MaxDepth	Deepest a hit pushes inside the box, cm. 0 uses the profile’s Max Displacement.	0
FCFStiffnessZone::bMirrored	Also applies reflected across Y = 0.	Off
UCFEditorSettings::ZonePresets	Presets in the zone menu: Frame (stiffness 3), Cabin (2, depth 12 cm), Crumple (0.5) and Neutral (1).	The four above

Check that it works

1. Open the proving ground in Play In Editor with a car whose profile has the zones you made above.
2. Type Crushform.ShowZones 1. Each zone draws as a box coloured by its stiffness on a log scale: green at x1, through yellow and orange toward red, which is full red from x4 up. Below x1 the colour turns toward blue, and x0.25 and lower are full blue. Each box is labelled with its stiffness multiplier and, where it has one, its depth cap.

Crushform.ShowZones 1 in Play In Editor: each zone's box, coloured and labelled by its stiffness.

3. With a second car that has these zones in view, aim your car’s camera at a soft zone and type Crushform.DebugImpact 15. Then aim at a stiff zone and type it again at the same speed. The soft zone dents deeper. The command skips the car you drive, so your own car cannot be the target.

Crushform.ShowZones and Crushform.DebugImpact are cheats: they work in every build except Shipping, and in the editor.

Troubleshooting

The Zone Editor shows nothing in the level or in Play In Editor

Cause. The editor draws zones only in the Blueprint editor’s viewport. A selection on a level or in a running game draws nothing.

Fix. Open the vehicle’s Blueprint and select the component there.

The vehicle has no Stiffness Zones section to edit

Cause. The adapter’s Deform Profile is empty, or Dirt and Dents is off. The editor edits only the profile set on the adapter. Without it, the vehicle uses the project’s default profile, which is not the Blueprint’s to edit.

Fix. Set Deform Profile on the adapter, with Dirt and Dents on.

A zone shows “outside the lattice”

Cause. Part of the zone’s box lies past the lattice. The part past the lattice is ignored.

Fix. Move the box onto the body. If the body’s collision is larger than the lattice, widen Lattice Margin in the profile, or turn on Use Explicit Bounds and set Explicit Bounds.

A zone has no effect on a crush press or on the paint

Cause. A crush press ignores zones, by design. Zones divide the dent push of a hit only, and the paint wears as the metal moves inside a zone.

Fix. Nothing for the crush press. For the dents, change the zone’s Stiffness.