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Add a loot item

A loot item is two assets: a DA_Loot_* Data Asset that holds its price and how fragile it is, and a BP_Loot_* actor that holds its mesh and its weight. Copy the toolbox, change both, and add the actor to a loot table. It then spawns, gets damaged, sells and shows on the recap.

If you have not read How a run works, start there.

  • The Data Assets: Content/MPFriendslop/Blueprints/DataAssets/Loot/Childs/
  • The actors: Content/MPFriendslop/Blueprints/Environments/Loot/Childs/
  • The meshes: Content/MPFriendslop/Meshes/Props/Loot/
  • The loot tables: Content/MPFriendslop/Blueprints/DataAssets/LootTable/Childs/

Before you start

Import your mesh into Meshes/Props/Loot/ as SM_Loot_<Name>. Open it and give it a simple collision (a box, a sphere or a convex from the Collision menu). Loot is a physics object, and a mesh with no simple collision cannot simulate physics.

Step 1, the Data Asset

  1. In Blueprints/DataAssets/Loot/Childs/, duplicate DA_Loot_Toolbox.
  2. Name it DA_Loot_<Name>.
  3. Fill in the fields below.
Field What it does Shipped in DA_Loot_Toolbox
Base Value The price in perfect condition 120
Fragility The share of the value that one very hard hit removes, from 0 to 1. 0 means the item never loses value 0.1
Impact Speed Threshold Below this impact speed, in cm/s, a hit costs nothing 250
Reference Impact Speed The impact speed, in cm/s, that costs exactly Fragility 800
Impact Sound Played where the item hits, on every hit that costs value CUE_Impact_Metal
Display Name The name on the recap TOOLBOX

The shipped items all keep 250 and 800 and only change Base Value and Fragility: 0.03 on the hammer, 0.3 on the sample jar, 1.0 on the glass vase. The Settings|Breaking fields are for items that shatter, see Make a loot item breakable.

Impact Sound is played on the surface it hits. Give it an attenuation with occlusion off, like ATT_Impact on the shipped cues, or the surface muffles it to nothing.

Every DA_Loot_* is a BP_LootDataAsset. To start from an empty one instead of a copy, right click in Blueprints/DataAssets/Loot/Childs/, then Miscellaneous, then Data Asset, and pick BP_LootDataAsset. Its fields then start at the class defaults, so fill in every row of the table above.

Step 2, the actor

  1. In Blueprints/Environments/Loot/Childs/, duplicate BP_Loot_Toolbox.
  2. Name it BP_Loot_<Name>.
  3. Select Mesh and set its Static Mesh to your SM_Loot_<Name>.
  4. On Mesh, in the Physics section, type the weight in Mass (kg). Its override is already ticked.
  5. Select BP_LootValueComponent and set Loot Data to your DA_Loot_<Name>.

That is the whole actor. BP_Loot_Toolbox sets only those three things. Everything else comes from BP_LootBase: the physics and collision, the grab, the outline, and the noise enemies hear when a hit costs value.

The mass is what makes an item hard to carry. See How grabbing works, and tuning the weight.

Step 3, a loot table

  1. Open DA_LootTable_Salvage or DA_LootTable_Shelf.
  2. Add an element to Entries.
  3. Set Loot Class to BP_Loot_<Name> and give it a Weight.

A weight of 3 is three times as likely as a weight of 1. DA_LootTable_Salvage is used by the points on the floor. DA_LootTable_Shelf is used by the points on furniture and shelves, and leaves out the heavy items. An item that is in no table only appears where you drop it in the level by hand. More on tables in Place loot spawn points and loot tables.

Changing the feedback

The red flash, the -$N number and the timing are on BP_LootValueComponent. Change them on the component of your actor, or on BP_LootBase for every item.

Field What it does
Impact Cooldown The minimum time between two hits that cost value. 0.25 seconds, so an item landing flat is not charged once per corner
Impact Flash Material The overlay flashed on the item when it loses value. Ships as M_ImpactFlash
Impact Flash Duration How long the flash stays. 0.45 seconds
Impact Value Popup Class The actor spawned at the hit point to show the loss. Ships as BP_ImpactValuePopup

To replace the -$N number with your own effect, make an actor that implements BPI_ImpactValue, fill its Show Impact Value event (it receives the dollars lost as Value), and set it as Impact Value Popup Class.

To react in your own Blueprints, bind these on BP_LootValueComponent:

Dispatcher When it fires Fires on
OnConditionChanged The condition changed. Gives New Condition, from 0 to 1 every player
OnImpact A hit cost value. Gives the Hit, the Impact Speed and the Condition Loss. A hit that costs nothing does not fire it every player
OnBroken The item shatters, just before it is destroyed every player
OnExtracted The item is sold in the chute, just before it is destroyed. Gives the Value every player

Get Current Value and Get Display Name on the same component give you the price right now and the name, on any machine.

Warning

Fragility at 0 also means silent. The impact sound, the flash, the number and OnImpact only happen when a hit costs value, so an item with Fragility 0 never makes an impact sound. There is no error.

Make it glow

BP_Loot_WardenHead and the arena crown wear an aura: a golden halo, sparkles that rise from it, and a warm light around the item. Any loot item can wear it.

  1. Open your loot Blueprint. Click Add, then pick Niagara Particle System Component. Name it Aura.
  2. Set its Niagara System Asset to NS_Loot_Aura, found in Content/MPFriendslop/Niagara/Loot/.
  3. Move it to the centre of your mesh.

Two parameters change the look, per item, under User Parameters in the Details panel of the component:

Parameter What it does Default
AuraTint The colour of the halo and the sparkles. Values above 1 brighten them gold, (1, 0.55, 0.06)
LightColor The colour and strength of the light around the item (60, 33, 3.6)

The light of a particle system goes out as soon as the item leaves the screen, even on the walls you still see. For a light that stays, set LightColor to black and add a Point Light component, as BP_Crown does with its Glow light.

Giving a value to your own actor

Any actor can be sold, not only children of BP_LootBase.

  1. Make it grabbable first, with a mesh that has Simulate Physics ticked and the actor set to Replicates: see Make any actor grabbable.
  2. Add a BP_LootValueComponent and set its Loot Data.
  3. Keep Component Replicates ticked on the component. It is ticked by default.

The component only listens to meshes that simulate physics when the game starts. A mesh that starts frozen and turns physics on later never takes damage.

Selling in the chute only needs the component. Two other checks need more:

  • To be counted as left behind on the recap, the actor also needs BPI_Grabbable.
  • To be seen as dropped on the trap, it needs BPI_Grabbable and a collision object type from the trap's Detection Object Types. These are WorldDynamic, Pawn and PhysicsBody by default.

Warning

Without Replicates on the actor, or with Component Replicates unticked, the server still damages and sells the item, but no other player ever sees its condition change, the flash or the number. There is no error.

To make your item shatter, see Make a loot item breakable.

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