Ok, let’s get some math going…
let’s implement the case where sunset and dusk is cut out from the nighttime, so we get longer days like in minecraft. here’s a sketch:
For ease of calculation we keep TimeOfDay between 0.0 and 1.0 - 0.0 is the start of day when the sun is directly at the horizont, 0.25 is midday, at 0.5 the sun touches the horizont again and the other half of the day begins - the half that includes dusk/nighttime/sunset.
And while we’re at it, let’s also calculate a sky color by blending between colors assigned to daytime, midday, nighttime.
I’m also creating a moon and sun object, a floor and the lights in this example code, so you can drop it onto a Cube representing the player in an empty scene to test it.
The radius is the distance of the sun/moon from the player and is kept small here, so the positions can be inspected while testing without the need for a first person controller or the like to look around.
Users of Unity Free will only see one light/shadow while testing this script - they need to disable one of the lights to see the other take effect.
I’m attaching the lights to the moon/sun, which is not really needed as the position of directional lights don’t matter.
using UnityEngine;
using System.Collections;
public class DayNight : MonoBehaviour {
void Start()
{
// Creating everything needed to demonstrate this from a single cube
player = this.transform;
GameObject floor = GameObject.CreatePrimitive(PrimitiveType.Plane);
floor.transform.position = player.position + 0.5f*Vector3.down;
sun = GameObject.CreatePrimitive(PrimitiveType.Sphere);
sun.name = "sun";
sun.renderer.material.color=Color.yellow;
sun.AddComponent<Light>().type = LightType.Directional;
sun.light.shadows = LightShadows.Hard;
sun.light.color = new Color(1,1,0.5f);
sun.renderer.castShadows = false;
moon = GameObject.CreatePrimitive(PrimitiveType.Sphere);
moon.name = "moon";
moon.renderer.material.color=new Color(0.75f,0.75f,0.75f);
moon.AddComponent<Light>().type = LightType.Directional;
moon.light.shadows = LightShadows.Hard;
moon.light.color = new Color(0.5f,0.5f,0.5f);
moon.light.intensity = 0.1f;
moon.renderer.castShadows = false;
}
public Transform player;
public GameObject sun;
public GameObject moon;
public float radius = 6;
public Color daytimeSkyColor = new Color(0.31f, 0.88f, 1f);
public Color middaySkyColor = new Color(0.58f, 0.88f, 1f);
public Color nighttimeSkyColor = new Color(0.04f, 0.19f, 0.27f);
// implementing minecraft PC defaults
public const float daytimeRLSeconds = 10.0f * 60;
public const float duskRLSeconds = 1.5f * 60;
public const float nighttimeRLSeconds = 7.0f * 60;
public const float sunsetRLSeconds = 1.5f * 60;
public const float gameDayRLSeconds = daytimeRLSeconds + duskRLSeconds + nighttimeRLSeconds + sunsetRLSeconds;
public const float startOfDaytime = 0;
public const float startOfDusk = daytimeRLSeconds / gameDayRLSeconds;
public const float startOfNighttime = startOfDusk + duskRLSeconds / gameDayRLSeconds;
public const float startOfSunset = startOfNighttime + nighttimeRLSeconds / gameDayRLSeconds;
private float timeRT = 0;
public float TimeOfDay // game time 0 .. 1
{
get { return timeRT/gameDayRLSeconds; }
set { timeRT = value*gameDayRLSeconds; }
}
void Update () {
timeRT = (timeRT+Time.deltaTime) % gameDayRLSeconds;
Camera.main.backgroundColor = CalculateSkyColor();
float sunangle = TimeOfDay * 360;
float moonangle = TimeOfDay * 360 + 180;
Vector3 midpoint = player.position; midpoint.y -= 0.5f; //midpoint = playerposition at floor height
sun.transform.position = midpoint + Quaternion.Euler(0,0,sunangle)*(radius*Vector3.right);
sun.transform.LookAt(midpoint);
moon.transform.position = midpoint + Quaternion.Euler(0,0,moonangle)*(radius*Vector3.right);
moon.transform.LookAt(midpoint);
}
Color CalculateSkyColor()
{
float time = TimeOfDay;
if (time <= 0.25f)
return Color.Lerp(daytimeSkyColor, middaySkyColor, time/0.25f);
if (time <= 0.5f)
return Color.Lerp(middaySkyColor, daytimeSkyColor, (time-0.25f)/0.25f);
if (time <= startOfNighttime)
return Color.Lerp(daytimeSkyColor, nighttimeSkyColor, (time-startOfDusk)/(startOfNighttime-startOfDusk));
if (time <= startOfSunset) return nighttimeSkyColor;
return Color.Lerp(nighttimeSkyColor, daytimeSkyColor, (time-startOfSunset)/(1.0f-startOfSunset));
}
void OnGUI()
{
Rect rect = new Rect(10, 10, 120, 20);
GUI.Label(rect, "time: " + TimeOfDay); rect.y+=20;
GUI.Label(rect, "timeRT: " + timeRT);
rect = new Rect(120, 10, 200, 10);
TimeOfDay = GUI.HorizontalSlider(rect, TimeOfDay, 0, 1);
}
}