IVMI-builder

(work in progress)

IVMI-builder is a free-software framework that facilitates the design of Immersive Virtual Musical Instruments. It relies on the Godot game engine and the PureData audio programming language.

Prerequisites

• PureData from https://puredata.info
• Godot 4.x from https://godotengine.org/, with OpenXR activated
• If you want to be able to integrate the audio when releasing your instrument (e.g. in a binary or as an app), install the Gdpd addon

A first example

Scene creation

Patch creation

Design process

Release

Creating your instrument

Godot IvmiScene

The root of your scene must extend from the IvmiScene class/script. Attach a script to it and start it with :

extends IvmiScene

func _ready() :
	super._ready()


func _process(delta) :
	super._process(delta)

Then your scene tree can look like :

• Main (with attached script extending IvmiScene)
  • XROrigin
    • XRCamera
    • XRController
    • MeshInstance

You can also directly attach the script extending IvmiScene to the ARVROrigin node.

IvmiScene provides a number of settings to help you design immersive instruments , such as :

• Pd Mode
• Pd Patch
• XR Mode
• ...

Godot IvmiNode

IVMI-node are the main components of any IVMI instruments. IVMI-node contains IVMI-properties. By inheriting IVMI-node.gd you are able to define a specific behavior/feedback for each IVMI-property change that occur within the node. You can for example write a code that change the size of the node's mesh when the node is selected.

extends IvmiNode

func _ready():
    # Call default IvmiNode constructor
    super._ready()

	# Optionally define a node type
	_set_ivmi_type("my_node")
	
	# Add custom properties with array of values
	_add_property("selected", [0])
    
    # Properties are sent by default, optionnally deactivate sending
    _properties["selected"].set_listen(false)
	
    
func process(delta) : 
    # Call default IvmiNode processing, required for updates
    super._process(delta)
    

func _set_property(prop, vals) :
	# Call default properties handling
	super._set_property(prop, vals)
	
	# Handle custom properties
	match prop:
        "selected":
            get_node("MeshInstance").scale.x = 2.0*vals[0]+1.0

IvmiProperty

IvmiProperties are composed of :

• A name : A string
• Values : An array of values (floats, ints, bools, strings, ...)

Each property change is sent to Pure Data, when their _listen variable is set to true, which is the case by default.

# Add a new property
_add_property("radius", [1])
# Retrieve property values
radius = _get_property("radius")[0]
# Set a property
set_property("radius",[0.5])

PureData ivmi_scene

PureData ivmi_node

PureData ivmi_property

Rendering

Mono

SteamVR headsets

TODO

Android based headset

TODO

Stereoscopic displays

Multi-user Instruments

Using 3D Interaction Techniques

Using PureData abstractions