Create the Soldier

Complete Create the First Level first. You now have a running scene and camera controls. This chapter adds a Soldier you can see and select. You will give it a movement ability next.

1. Create the unit Blueprint

In Content/Demo/Blueprints, right-click and choose SeinARTS Entity Blueprint from the SeinARTS asset category. Choose Generic Entity in the parent picker and name the asset SU_Soldier.

Open it. Its parent is the native SeinActor, and it already has an inherited EntityBridge component. The bridge connects this actor to its simulation entity. Add the unit’s data through the Blueprint’s Components panel.

Add Sein Identity, select it, and enter:

Field	Value
Display Name	Soldier
Description	A basic soldier unit.

The entity factory generates SeinARTS.Unit.Soldier from the asset name. This tag identifies the unit type; Display Name is the readable label you will use in the UI.

Compile and save.

2. Add the mannequin mesh

Use Unreal’s Third Person content for the Soldier’s model and animations. In the Content Browser, choose Add > Add Feature or Content Pack, select Third Person in the Blueprint category, and choose Add to Project.

The pack adds its mannequin assets under Content/Characters/Mannequins. Your existing demo game mode and controller remain the classes used by LVL_DemoSkirmish.

Return to SU_Soldier. Add a Skeletal Mesh component, name it SoldierMesh, and assign SKM_Manny_Simple from Content/Characters/Mannequins/Meshes.

Set the mesh’s relative Yaw to -90.

This keeps the feet at the actor’s origin and aligns the mannequin with the unit’s forward direction.

3. Create the idle animation Blueprint

Create Content/Demo/Animations now. Inside it, create an Animation Blueprint, choose the imported mannequin’s SK_Mannequin skeleton, and name it ABP_Soldier.

Open its AnimGraph. In the Asset Browser, find MM_Idle, drag it into the graph as an animation sequence player, and connect its pose output to Output Pose. Select the sequence player and enable Loop Animation.

Compile and save ABP_Soldier.

Return to SU_Soldier and select SoldierMesh. Set Animation Mode to Use Animation Blueprint, then assign ABP_Soldier as Anim Class. The preview should show the mannequin standing in its idle animation.

This is the starting pose graph. When you add movement, you will extend this Animation Blueprint to read the unit’s simulation movement state and animate its locomotion.

4. Give the unit a selection shape

In SU_Soldier, add Sein Extents. Select it and add one entry to Shapes. The new entry is a capsule with radius 40 and height 180.

The capsule describes the unit’s body for the framework’s spatial queries, including selection. Its Height extends upward from Local Offset Z, so this shape starts at the Soldier’s feet.

The default Unrestricted selection policy allows normal selection, and Include in Drag Selection includes the unit in a marquee. You can select this Soldier without adding an Unreal collision capsule to the actor.

5. Add sight

Add Sein Vision to the Blueprint. Its Vision Stamps array starts with one enabled radial stamp with radius 1000 on the normal sight layer. That stamp makes the Soldier a source of vision for its owning player. You can adjust its radius and shape in Vision Stamps as you develop the unit.

Compile and save SU_Soldier.

6. Set the player’s starting entity

Open LVL_DemoSkirmish and select the Sein Player Start you created earlier. Set Spawn Entity to SU_Soldier. Its Player Slot remains 1.

Position the start inside the baked playable bounds, with its actor origin at the floor’s top surface. If the floor surface is at Z 0, set the start’s Location Z to 0. The Soldier’s feet are at its origin, and the starting entity uses the start’s saved transform directly. Use zero rotation and unit scale for this checkpoint.

Save the map. When the match starts, the framework spawns the Soldier at this start and assigns it to Player Slot 1. The map defines the player’s starting presence through Spawn Entity; subsequent units will come from gameplay such as production.

7. Test selection

Compile and save the unit and animation Blueprints, then save the map.

Run the scene with one player in Play Standalone, as in the previous chapter. Pan to the Soldier and confirm that it stands on the floor and plays its idle animation.

To check selection before building a selection display, open the Unreal console and run these two toggle commands once each:

Sein.Commands.ShowLog
Sein.Commands.ShowLog.Observer

The first shows the command log overlay. The second includes observer commands, which contain local selection changes.

Close the console, then:

1. Left-click the Soldier. The overlay should report SelectionChanged with 1 ents.
2. Left-click clear ground. It should report SelectionChanged with 0 ents.
3. Drag a marquee around the Soldier and release. Selection should return to 1 ents.

These commands toggle their settings, so run them again to turn the diagnostics off after the check. The Soldier has no movement ability yet; this chapter’s test is selection.

Checkpoint

• SU_Soldier is your own Blueprint derived from SeinActor.
• Its mesh uses the imported mannequin and your ABP_Soldier idle graph.
• Sein Extents contains a capsule, and Sein Vision contains a radial stamp.
• The Sein Player Start references SU_Soldier as Spawn Entity, and the match spawns it for Player Slot 1 at the start’s saved transform.
• Clicking, clearing selection, and marquee selection produce the expected selection counts.

Continue with Add Movement to author SA_Move, connect right-click commands, and animate locomotion.