Lesson 2.10: Project - Biome Encounters

In this final lesson of Level 2, we’ll combine everything you’ve learned—traits, state, logic, NPCs, and zones—to create a dynamic environment that changes its inhabitants based on where you are.

The Goal

Build an environment with two biomes: a Lush Forest and a Dead Desert.

• Entering the Forest biome spawns "Deer" NPCs.
• Entering the Desert biome spawns "Scorpion" NPCs.
• The player's movement speed decreases in the Desert.

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Step 1: Define the Biome Zones

We use the zone block to define physical areas and the state block to track the current active biome.

composition "Biome Demo" {
    state {
        currentBiome: "none"
    }

    // Forest Zone
    zone "ForestBiome" {
        position: [-20, 0, 0]
        size: [20, 10, 20]
        color: "#228B22"

        on_enter {
            state.currentBiome = "forest"
            emit "ui_overlay" "Entering Lush Forest"
        }
    }

    // Desert Zone
    zone "DesertBiome" {
        position: [20, 0, 0]
        size: [20, 10, 20]
        color: "#EDC9AF"

        on_enter {
            state.currentBiome = "desert"
            emit "ui_overlay" "Entering Scorched Desert"
            Player.walkSpeed = 1.0  // Slow down
        }
        on_exit {
            Player.walkSpeed = 2.0  // Resume speed
        }
    }
}

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Step 2: Create the Dynamic Spawner

We'll use a logic block with an on_tick or a custom event to spawn NPCs based on the state.currentBiome.

logic {
    on_biome_pulse() {
        if (state.currentBiome == "forest") {
            spawn_npc("Deer", random_pos_in_zone("ForestBiome"))
        } else if (state.currentBiome == "desert") {
            spawn_npc("Scorpion", random_pos_in_zone("DesertBiome"))
        }
    }

    // Run every 5 seconds
    timeline "SpawnerTimer" {
        autoplay: true
        loop: true
        5.0: { call: "on_biome_pulse()" }
    }
}

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Step 3: Define the NPCs

We need to define the templates for our NPCs so the engine knows what to create.

template "Deer" {
    @spatial_agent @passive
    model: "models/deer.glb"

    behavior "Wander" {
        trigger: "idle"
        actions: [{ move: { target: random_pos(10), speed: 1.0 } }, { wait: 2.0 }]
    }
}

template "Scorpion" {
    @spatial_agent @hostile
    model: "models/scorpion.glb"

    behavior "Hunt" {
        trigger: "on_vision"
        target: "Player"
        actions: [{ move: { target: "Player", speed: 2.5 } }]
    }
}

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Step 4: Adding Environmental Effects

To make the biomes feel real, add environment properties that change with the state.

environment {
    @bind(state.currentBiome, "getBiomeColor") : backgroundColor
}

// In your helper scripts:
function getBiomeColor(biome) {
    if (biome == "forest") return "#1a3300";
    if (biome == "desert") return "#5a4d00";
    return "#80c5de"; // default sky
}

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Summary

By completing this project, you’ve mastered:

• Spatial Awareness: Using zone to trigger logic based on player location.
• Global State: Tracking environment states across multiple objects.
• Dynamic Entities: Spawning npc templates via logic and timeline.
• Environmental Feedback: Changing player stats and visuals based on the biome.

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🎉 Congratulations!

You have completed Academy Level 2 (Intermediate).

What's Next?

In Level 3 (Advanced), we will dive into:

• Custom Shader Traits (@shader).
• Cross-Domain Logic Federation.
• Decentralized World Management with ZK-Privacy.

Keep building!

Next Lesson

In Lesson 2.11: Publishing to HoloHub, you'll package your compositions for the HoloHub registry — metadata traits, versioning, and portfolio scenes.

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Estimated time: 60 minutes Difficulty: ⭐⭐⭐ Intermediate+