extensions

Sky


Table of contents

Sky material

Sky Material

Introduction

The sky material allows to create dynamic and texture free effects for skyboxes.

This work is based on "A Practical Analytic Model for Daylight". First implemented by Simon Wallner, improved by Martin Upitis and finally implmented in Three.js by zz85

The challenge for skyboxes is to reproduce and configure the sky taking care of the atmosphere state. In other words, for example, determine how the light (from sun) is scattered by particles.

Playground example

A Playground example can be found here: Animate the sky -


Just press the following keys:

  • 1: Set Day
  • 2: Set Evening
  • 3: Increase Luminance
  • 4: Decrease Luminance
  • 5: Increase Turbidity
  • 6: Decrease Turbidity

How to use?

Simply create a skybox and assign a new instance of the Sky Material:

var skyMaterial = new BABYLON.SkyMaterial("skyMaterial", scene);
skyMaterial.backFaceCulling = false;

var skybox = BABYLON.Mesh.CreateBox("skyBox", 1000.0, scene);
skybox.material = skyMaterial;

That's all!

Configuring the Sky Material

The aspect of the sky can be customized, including the day/night time. The properties are:

skyMaterial.turbidity = 1; // Represents the amount (scattering) of haze as opposed to molecules in atmosphere

skyTurbidity

skyMaterial.luminance = 1; // Controls the overall luminance of sky in interval ]0, 1,190[

skyLuminance

// Control the planet's orientation over the sun
skyMaterial.inclination = 0.5; // The solar inclination, related to the solar azimuth in interval [0, 1]
skyMaterial.azimuth = 0.25; // The solar azimuth in interval [0, 1]

Otherwise, if you want to configure the sun position with a BABYLON.Vector3, you can set:

// Manually set the sun position
skyMaterial.useSunPosition = true; // Do not set sun position from azimuth and inclination
skyMaterial.sunPosition = new BABYLON.Vector3(0, 100, 0);

skyAzimuthInclination

skyMaterial.rayleigh = 2; // Represents the sky appearance (globally)

skyRayleigh

// Mie scattering (from [Gustav Mie](https://en.wikipedia.org/wiki/Gustav_Mie))
// Related to the haze particles in atmosphere

// The amount of haze particles following the Mie scattering theory
skyMaterial.mieDirectionalG = 0.8;

skyMaterial.mieCoefficient = 0.005; // The mieCoefficient in interval [0, 0.1], affects the property skyMaterial.mieDirectionalG

skyMie