three.js实现辉光

在three.js中实现辉光效果可以使用ShaderMaterial和PostProcessing来实现。以下是一个简单的实现步骤：

1. 创建一个ShaderMaterial来渲染模型，该材质包含一个自定义的fragment shader，用于实现辉光效果。

const glowMaterial = new THREE.ShaderMaterial({
    uniforms: {
        "c": { type: "f", value: 0.2 },
        "p": { type: "f", value: 3.0 },
        glowColor: { type: "c", value: new THREE.Color(0xffffff) },
        viewVector: { type: "v3", value: camera.position }
    },
    vertexShader: document.getElementById('vertexShader').textContent,
    fragmentShader: document.getElementById('fragmentShader').textContent,
    side: THREE.FrontSide,
    blending: THREE.AdditiveBlending,
    transparent: true
});

2. 创建一个自定义的fragment shader，用于实现辉光效果。该shader通过计算法向量和视线向量之间的角度来确定辉光的大小和颜色。

uniform vec3 glowColor;
uniform vec3 viewVector;

varying vec3 vNormal;

void main()
{
    float intensity = pow(c - dot(vNormal, viewVector), p);
    gl_FragColor = vec4(glowColor, intensity);
}

3. 将该材质应用于模型上。

const mesh = new THREE.Mesh(geometry, glowMaterial);
scene.add(mesh);

4. 使用PostProcessing技术，在屏幕上渲染出辉光效果。这可以通过创建一个RenderPass和一个ShaderPass来实现。

const renderPass = new THREE.RenderPass(scene, camera);

const glowComposer = new THREE.EffectComposer(renderer);
glowComposer.addPass(renderPass);

const glowPass = new THREE.ShaderPass({
    uniforms: {
        "tDiffuse": { value: null },
        "glowColor": { value: new THREE.Color(0xffffff) }
    },
    vertexShader: document.getElementById('vertexShader').textContent,
    fragmentShader: document.getElementById('glowFragmentShader').textContent,
    blending: THREE.AdditiveBlending,
    transparent: true
});
glowComposer.addPass(glowPass);

const finalPass = new THREE.ShaderPass({
    uniforms: {
        "tDiffuse": { value: null },
        "tGlow": { value: glowComposer.renderTarget2.texture }
    },
    vertexShader: document.getElementById('vertexShader').textContent,
    fragmentShader: document.getElementById('finalFragmentShader').textContent
});
composer.addPass(finalPass);

5. 创建自定义的fragment shaders，用于在屏幕上渲染出辉光效果。

//glowFragmentShader
uniform vec3 glowColor;

varying vec2 vUv;

void main()
{
    vec4 sum = vec4(0.0);
    vec2 texelSize = vec2(1.0 / resolution.x, 1.0 / resolution.y);
    for (int i = -2; i <= 2; i++)
    {
        for (int j = -2; j <= 2; j++)
        {
            vec2 offset = vec2(float(i), float(j)) * texelSize;
            sum += texture2D(tDiffuse, vUv + offset);
        }
    }
    gl_FragColor = sum / 25.0;
    gl_FragColor += vec4(glowColor, 1.0);
}

//finalFragmentShader
uniform sampler2D tDiffuse;
uniform sampler2D tGlow;

varying vec2 vUv;

void main()
{
    vec4 texel = texture2D(tDiffuse, vUv);
    vec4 glow = texture2D(tGlow, vUv);
    gl_FragColor = texel + glow;
}

通过以上步骤，就可以在three.js中实现辉光效果了。