node_modules/three/src/renderers/shaders/ShaderLib/cube.glsl.js

export const vertex = /* glsl */`
varying vec3 vWorldDirection;

#include <common>

void main() {

	vWorldDirection = transformDirection( position, modelMatrix );

	#include <begin_vertex>
	#include <project_vertex>

	gl_Position.z = gl_Position.w; // set z to camera.far

}
`;

export const fragment = /* glsl */`
uniform samplerCube tCube;
uniform float tFlip;
uniform float opacity;

varying vec3 vWorldDirection;

void main() {

	vec4 texColor = textureCube( tCube, vec3( tFlip * vWorldDirection.x, vWorldDirection.yz ) );

	gl_FragColor = texColor;
	gl_FragColor.a *= opacity;

	#include <tonemapping_fragment>
	#include <colorspace_fragment>

}
`;