Galaxy1Controller.cs

#region Copyright

// Copyright 2014 Michael A. R. Duncan
// You are free to do whatever you want with this source
// File: Galaxy1Controller.cs

#endregion

#region

using Assets.MickyD.Scripts;
using UnityEngine;

#endregion

public class Galaxy1Controller : MonoBehaviour
{
	private const int GroupSize = 128;
	private const int QuadStride = 12;

	#region Fields

	/// <summary>
	///     The galaxy radius
	/// </summary>
	/// <remarks>This will appear as a Property Drawer in Unity 4</remarks>
	[Range(10, 1000)]
	public float GalaxyRadius = 200;

	public Texture2D HueTexture;

	public int NumStars = 10000;

	public ComputeShader StarCompute;
	public Material StarMaterial;

	private GameManager _manager;
	private ComputeBuffer _quadPoints;
	private Star[] _stars;
	private ComputeBuffer _starsBuffer;
	private int _updateParticlesKernel;

	#endregion

	// Use this for initialization

	#region Properties

	private Vector3 StartPointA
	{
		get { return new Vector3(GalaxyRadius, 0, 0); }
	}

	private Vector3 StartPointB
	{
		get { return new Vector3(-GalaxyRadius, 0, 0); }
	}

	#endregion

	#region Methods

	private void CreateStars(int offset, int count, Vector3 T, Vector3 V)
	{
		for (var i = offset; i < offset + count; i++)
		{
			var star = _stars[i];
			star.color = Vector3.one; // white
			star.position = Random.insideUnitSphere*GalaxyRadius + T;
			star.velocity = V;

			_stars[i] = star;
		}
	}

	private void OnDestroy()
	{
		// must deallocate here
		_starsBuffer.Release();
		_quadPoints.Release();
	}

	private void OnDrawGizmos()
	{
		Gizmos.color = Color.yellow;
		Gizmos.DrawWireSphere(transform.position, GalaxyRadius);
		Gizmos.DrawWireSphere(transform.position + StartPointA, GalaxyRadius);
		Gizmos.DrawWireSphere(transform.position + StartPointB, GalaxyRadius);
	}

	private void OnRenderObject()
	{
		if (!SystemInfo.supportsComputeShaders)
		{
			return;
		}

		// bind resources to material
		StarMaterial.SetBuffer("stars", _starsBuffer);
		StarMaterial.SetBuffer("quadPoints", _quadPoints);

		// set the pass
		StarMaterial.SetPass(0);

		// draw
		Graphics.DrawProcedural(MeshTopology.Triangles, 6, NumStars);
	}

	private void Start()
	{
		_updateParticlesKernel = StarCompute.FindKernel("UpdateStars");
		if (_updateParticlesKernel == -1)
		{
			Debug.LogError("Failed to find UpdateStars kernel");
			Application.Quit();
		}

		_starsBuffer = new ComputeBuffer(NumStars, Constants.StarsStride);

		_stars = new Star[NumStars];
		var n = NumStars/2;
		var offset = 0;
		CreateStars(offset, n, StartPointA, new Vector3(-10, 5, 0));
		offset += n;

		CreateStars(offset, n, StartPointB, new Vector3(10, -5, 0));

		_starsBuffer.SetData(_stars);

		_quadPoints = new ComputeBuffer(6, QuadStride);
		_quadPoints.SetData(new[]
		{
			new Vector3(-0.5f, 0.5f),
			new Vector3(0.5f, 0.5f),
			new Vector3(0.5f, -0.5f),
			new Vector3(0.5f, -0.5f),
			new Vector3(-0.5f, -0.5f),
			new Vector3(-0.5f, 0.5f),
		});

		_manager = FindObjectOfType<GameManager>();
	}

	private void Update()
	{
		// bind resources to compute shader
		StarCompute.SetBuffer(_updateParticlesKernel, "stars", _starsBuffer);
		StarCompute.SetFloat("deltaTime", Time.deltaTime*_manager.MasterSpeed);
		StarCompute.SetTexture(_updateParticlesKernel, "hueTexture", HueTexture);

		// dispatch, launch threads on GPU
		var numberOfGroups = Mathf.CeilToInt((float) NumStars/GroupSize);
		StarCompute.Dispatch(_updateParticlesKernel, numberOfGroups, 1, 1);
	}

	#endregion
}