three.js/src/renderers/shaders/ShaderChunk/dithering_pars_fragment.glsl.js

export default /* glsl */`
#ifdef DITHERING

	// based on https://www.shadertoy.com/view/MslGR8
	vec3 dithering( vec3 color ) {
		//Calculate grid position
		float grid_position = rand( gl_FragCoord.xy );

		//Shift the individual colors differently, thus making it even harder to see the dithering pattern
		vec3 dither_shift_RGB = vec3( 0.25 / 255.0, -0.25 / 255.0, 0.25 / 255.0 );

		//modify shift according to grid position.
		dither_shift_RGB = mix( 2.0 * dither_shift_RGB, -2.0 * dither_shift_RGB, grid_position );

		//shift the color by dither_shift
		return color + dither_shift_RGB;
	}

#endif
`;