Unity SteamVR Simple 3D Sketching Tool

VRSimpleSketch.cs

// Instructions:
// Just attach this script to your SteamVR Controller (left or right) and then you can draw in 3D.
// After you attach it, a new GameObject called "Sketch Line" will be added as a child.
// You'll want to adjust the material and width of the line renderer to make it look nice.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class VRSimpleSketch : MonoBehaviour {

	// Keep track of our child object that holds the current line
	private GameObject _currentChildObject;
	// ...and the LineRenderer on it.
	private LineRenderer _lineRenderer;
	
	private SteamVR_TrackedController _controller;

	public bool justOneLine = false;
	public bool pretendPenDown = false;
	
	private bool penDown;
	private bool penWasDown;

	// This is called in the Editor when this script is 1st attached to a GameObject
	void Reset() {
		if (_currentChildObject == null) {
			var lines = GetComponentsInChildren<LineRenderer>();
			if (lines.Length > 0) {
				// We already have one (or more) so pick one
				_lineRenderer = lines[0];
				_currentChildObject = _lineRenderer.gameObject;
			}else{
				MakeNewLineObject();
			}
		}
		_controller = GetComponent<SteamVR_TrackedController>();
	}

	void OnEnable () {
		Reset();
	}

	void MakeNewLineObject() {
		if (_currentChildObject != null) {
			// Copy the previous one
			_currentChildObject = Instantiate(_currentChildObject);
			_lineRenderer = _currentChildObject.GetComponent<LineRenderer>();
		}else{
			// Make a brand new one
			_currentChildObject = new GameObject("Sketch Line");
			_lineRenderer = _currentChildObject.AddComponent<LineRenderer>();
		}
		_currentChildObject.transform.position = transform.position;
		_currentChildObject.transform.parent = transform;
	}
	
	void Update () {
		// If there is no _controller, you can use pretendPenDown to simulate it
		penDown = (_controller != null && _controller.triggerPressed) || pretendPenDown;

		if (penDown) {
			if (penWasDown) {
				ExtendLine(transform.position);
			}else{
				if (!justOneLine) MakeNewLineObject();
				StartLine(transform.position);
			}
		}else{
			if (penWasDown) {
				// The pen was just released.
			}
		}

		penWasDown = penDown;
	}

	public void StartLine(Vector3 startPoint) {
		var points = new Vector3[1];
		points[0] = startPoint;
		_lineRenderer.positionCount = 1;
		_lineRenderer.SetPositions(points);
	}

	public void ExtendLine(Vector3 newPoint) {
		int oldPointCount = _lineRenderer.positionCount;

		// Make an array with enough room for one more point
		var points = new Vector3[oldPointCount+1];
		
		// Get all the old points
		_lineRenderer.GetPositions(points);

		// Add the new one
		points[oldPointCount] = newPoint;

		_lineRenderer.positionCount = oldPointCount+1;
		_lineRenderer.SetPositions(points);
	}
}