three.js/src/renderers/shaders/ShaderLib/depth_vert.glsl.js

export default /* glsl */`
#include <common>
#include <uv_pars_vertex>
#include <displacementmap_pars_vertex>
#include <morphtarget_pars_vertex>
#include <skinning_pars_vertex>
#include <logdepthbuf_pars_vertex>
#include <clipping_planes_pars_vertex>

// This is used for computing an equivalent of gl_FragCoord.z that is as high precision as possible.
// Some platforms compute gl_FragCoord at a lower precision which makes the manually computed value better for
// depth-based postprocessing effects. Reproduced on iPad with A10 processor / iPadOS 13.3.1.
varying vec2 vHighPrecisionZW;

void main() {

	#include <uv_vertex>

	#include <skinbase_vertex>

	#ifdef USE_DISPLACEMENTMAP

		#include <beginnormal_vertex>
		#include <morphnormal_vertex>
		#include <skinnormal_vertex>

	#endif

	#include <begin_vertex>
	#include <morphtarget_vertex>
	#include <skinning_vertex>
	#include <displacementmap_vertex>
	#include <project_vertex>
	#include <logdepthbuf_vertex>
	#include <clipping_planes_vertex>

	vHighPrecisionZW = gl_Position.zw;

}
`;