Object-Template Pattern Reference (.holo)

Alternative .holo syntax using object and template keywords for reusability.

Overview

The .holo format supports two patterns:

1. Entity-Trait Pattern - Each entity unique (reference)
2. Object-Template Pattern - Reusable templates (THIS PAGE)

Basic Template

composition Scene {
  template GrabbableBall {
    mesh: {
      type: "sphere",
      radius: 0.3
    }

    grabbable: {
      enabled: true,
      grab_type: "physics"
    }

    rigidbody: {
      mass: 1.0,
      gravity_enabled: true
    }
  }

  object RedBall using GrabbableBall {
    advanced_pbr: {
      base_color: [1.0, 0.0, 0.0]
    }

    transform: {
      position: [-1.0, 1.0, 0.0]
    }
  }

  object BlueBall using GrabbableBall {
    advanced_pbr: {
      base_color: [0.0, 0.0, 1.0]
    }

    transform: {
      position: [1.0, 1.0, 0.0]
    }
  }
}

Template with Event Handlers

template InteractiveButton {
  mesh: {
    type: "box",
    width: 0.3,
    height: 0.1,
    depth: 0.3
  }

  pokeable: {
    enabled: true,
    press_depth: 0.02
  }

  on_poke_start(event) {
    this.onButtonPress();
  }

  onButtonPress() {
    // Override this in object instances
    console.log("Button pressed");
  }
}

object StartButton using InteractiveButton {
  transform: {
    position: [-1.0, 1.5, -3.0]
  }

  onButtonPress() {
    console.log("START button pressed!");
    // Custom logic for start button
  }
}

Property Overrides

Objects can override any template property:

template BaseBall {
  mesh: {
    type: "sphere",
    radius: 0.5
  }

  advanced_pbr: {
    base_color: [1.0, 1.0, 1.0],
    metallic: 0.2,
    roughness: 0.6
  }
}

object LargeRedBall using BaseBall {
  // Override mesh radius
  mesh: {
    type: "sphere",
    radius: 1.0  // Override
  }

  // Override color
  advanced_pbr: {
    base_color: [1.0, 0.0, 0.0]  // Override
  }
}

Complete Example

composition VRPlayground {
  template GrabbableBall {
    mesh: {
      type: "sphere",
      radius: 0.3
    }

    advanced_pbr: {
      base_color: [1.0, 1.0, 1.0],
      metallic: 0.2,
      roughness: 0.6
    }

    rigidbody: {
      mass: 1.0,
      gravity_enabled: true,
      linear_drag: 0.05,
      angular_drag: 0.05
    }

    collider: {
      type: "sphere",
      is_trigger: false,
      material: {
        friction: 0.5,
        bounciness: 0.7
      }
    }

    grabbable: {
      enabled: true,
      grab_type: "physics",
      haptic_on_grab: true,
      release_velocity_scale: 5.0
    }

    on_grab(event) {
      console.log("Ball grabbed");
    }

    on_release(event) {
      console.log("Ball released");
    }
  }

  object Floor {
    mesh: {
      type: "plane",
      width: 20.0,
      height: 20.0
    }

    advanced_pbr: {
      base_color: [0.16, 0.16, 0.23],
      metallic: 0.0,
      roughness: 0.9
    }

    transform: {
      position: [0.0, 0.0, 0.0]
    }

    collider: {
      type: "box",
      size: [20.0, 0.1, 20.0]
    }
  }

  object RedBall using GrabbableBall {
    advanced_pbr: {
      base_color: [1.0, 0.27, 0.27]
    }

    transform: {
      position: [-1.0, 1.0, -2.0]
    }
  }

  object GreenBall using GrabbableBall {
    advanced_pbr: {
      base_color: [0.27, 1.0, 0.27]
    }

    transform: {
      position: [0.0, 1.0, -2.0]
    }
  }

  object BlueBall using GrabbableBall {
    advanced_pbr: {
      base_color: [0.27, 0.27, 1.0]
    }

    transform: {
      position: [1.0, 1.0, -2.0]
    }
  }

  object MainLight {
    light: {
      type: "point",
      color: [1.0, 1.0, 1.0],
      intensity: 1.0,
      range: 20.0,
      cast_shadows: true
    }

    transform: {
      position: [0.0, 4.0, 0.0]
    }
  }
}

Entity vs Object Pattern

Aspect	Entity Pattern	Object Pattern
Reusability	Low	High
Clarity	High	Medium
Best for	Unique objects	Similar objects
Templates	No	Yes
Verbosity	Higher	Lower

When to Use Object Pattern

Use object+template pattern when:

• Many similar objects exist
• Template reusability is needed
• Migrating from .hsplus format
• Hybrid approach required (some templated, some unique)

Next Steps

• Entity-Trait Pattern
• Cross-Format Comparison
• Templates & Decorators (.hsplus)