[Three.js] Shader Material

A shader material is rendered with a custom shader. It requires vertex and fragment shaders which are written in GLSL (openGL Shading Language) code and depict the position of a vertex and its color, respectively. Since these codes run on the GPU using WebGL, a ShaderMaterial is rendered properly by WebGLRenderer only. In the post, I’ll explain how to use Shaders in Three.js.

ShaderMaterial can be defined by:

const material = new THREE.ShaderMaterial({
    uniforms: {
        time: { value: 1.0 },
        resolution: { value: new THREE.Vector2() }
    },
    vertexShader: /* glsl */ `...`,
    fragmentShader: /* glsl */ `...`,
})

The properties inside uniforms can be accessed in the vertexShader and fragmentShader, and they have the same values for each vertex. The types of GLSL variable are float, vec2, vec3, vec4, sampler2D, and their corresponding types for JavaScript are Number, THREE.Vector2, THREE.Vector3 (or THREE.Color), THREE.Vector4, and THREE.Texture.

GLSL JavaScript
float Number
vec2 THREE.Vector2
vec3 THREE.Vector3 or THREE.Color
vec4 THREE.Vector4
sampler2D THREE.Texture

The vertexShader and fragmentShader of ShaderMaterial fetch a code as a text format. These code can be written inside <script type=“x-shader/x-vertex”> or <script type=“x-shader/x-fragment”> in HTML, then be read by document.getElementById(’vertex’).textContent.

<!-- index.html -->
<html>
<head>
    <script id="vertex" type=“x-shader/x-vertex”>
        ...
    </script>
    <script id="fragment" type=“x-shader/x-fragment”>
        ...
    </script>
</head>
<body>
</body>
</html>

Otherwise, they can be declared as a multi-line strings using apostrophe (`) at an external file, then be imported as import vertex from ‘./shader/vertex.js’

// vertex.js
export const vertex = `
/* glsl */
...
`

In the following articles, I’ll introduce the basics of GLSL and create the Earth using ShaderMaterial.