Using three-fatline with Next.js

The error you're encountering is a common issue when using Three.js libraries in Next.js applications. The 'window is not defined' error occurs because Next.js performs server-side rendering (SSR), but Three.js and related packages like three-fatline are designed for browser environments and rely on browser-specific objects like window.

Solution: Dynamic Imports with Client-Side Only Rendering

You can solve this by using dynamic imports and ensuring the Three.js code only runs on the client side:

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'use client'; // If using the App Router

import { useEffect, useState } from 'react';
import dynamic from 'next/dynamic';

// Component that will contain your Three.js scene
const ThreeScene = () => {
  const [isClient, setIsClient] = useState(false);

  useEffect(() => {
    // This code only runs on the client
    setIsClient(true);
    
    // Import Three.js and three-fatline only on the client side
    if (typeof window !== 'undefined') {
      import('three').then((THREE) => {
        import('three-fatline').then((FatLine) => {
          // Your Three.js initialization code here
          // ...
        });
      });
    }
  }, []);

  if (!isClient) {
    return <div>Loading...</div>; // Or any loading state
  }

  return <div id="canvas-container" style={{ width: '100%', height: '500px' }} />;
};

// Use dynamic import with ssr: false for the component
const DynamicThreeScene = dynamic(() => Promise.resolve(ThreeScene), {
  ssr: false
});

export default function YourPage() {
  return (
    <div>
      <h1>My Three.js Scene</h1>
      <DynamicThreeScene />
    </div>
  );
}

Alternative Approach: Module Aliasing

You can also use module aliasing in your Next.js configuration to provide empty modules for browser-specific dependencies during server-side rendering:

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// next.config.js
module.exports = {
  webpack: (config, { isServer }) => {
    if (isServer) {
      // Replace three-fatline with an empty module on the server
      config.resolve.alias['three-fatline'] = require.resolve('./empty-module.js');
    }
    return config;
  },
};

Create an empty module file:

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// empty-module.js
module.exports = {};

Additional Considerations

1. Make sure to wrap your Three.js code in conditional checks:

   JSCopied
   if (typeof window !== 'undefined') {
     // Three.js code here
   }

2. For components that use Three.js, always use the 'use client' directive (if using App Router) or dynamic imports with ssr: false.

3. Consider using established Next.js + Three.js solutions like react-three-fiber, which handles many of these issues for you.

This approach should help you integrate three-fatline into your Next.js project while avoiding the 'window is not defined' error during server-side rendering.

Using three-fatline in Next.js: Handling 'window is not defined' Error

This is a common issue when using Three.js libraries in Next.js applications. The error occurs because Next.js performs server-side rendering (SSR), but Three.js and related packages like three-fatline are designed for browser environments and rely on browser-specific objects like window.

Solution: Dynamic Imports with Client-Side Only Rendering

The most effective approach is to use dynamic imports and only render your Three.js components on the client side:

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import dynamic from 'next/dynamic'

// Import your Three.js component with SSR disabled
const ThreeComponent = dynamic(
  () => import('../components/ThreeComponent'),
  { ssr: false }
)

export default function HomePage() {
  return (
    <div>
      <h1>My 3D Application</h1>
      <ThreeComponent />
    </div>
  )
}

Then in your ThreeComponent.js:

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import React, { useEffect, useRef } from 'react'
import * as THREE from 'three'
// Import three-fatline only on client side
import { FatLine } from 'three-fatline'

const ThreeComponent = () => {
  const mountRef = useRef(null)
  
  useEffect(() => {
    // Three.js code here
    // This will only run on the client
    const scene = new THREE.Scene()
    // Use FatLine here
    
    return () => {
      // Cleanup
    }
  }, [])
  
  return <div ref={mountRef} style={{ width: '100%', height: '500px' }} />
}

export default ThreeComponent

Alternative: Conditional Import

You can also conditionally import the library only when the window object is available:

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import { useEffect, useState, useRef } from 'react'
import * as THREE from 'three'

export default function ThreeComponent() {
  const mountRef = useRef(null)
  const [FatLine, setFatLine] = useState(null)
  
  useEffect(() => {
    // Import the library only on client side
    import('three-fatline').then(module => {
      setFatLine(module.FatLine)
    })
    
    // Rest of your Three.js initialization
    const scene = new THREE.Scene()
    // ...
    
    // Only use FatLine when it's available
    if (FatLine) {
      // Use FatLine here
    }
    
    return () => {
      // Cleanup
    }
  }, [FatLine])
  
  return <div ref={mountRef} style={{ width: '100%', height: '500px' }} />
}

This approach ensures that the code that depends on browser-specific APIs only runs in the browser environment, avoiding the "window is not defined" error during server-side rendering.

Remember that Three.js is primarily designed for web environments and relies on browser-specific objects and DOM APIs that aren't available in Node.js environments like Next.js server-side rendering.