blender-archive/source/blender/draw/engines/eevee/shaders/background_vert.glsl

in vec2 pos;

out vec3 viewPosition;

#ifndef VOLUMETRICS
/* necessary for compilation*/
out vec3 worldPosition;
out vec3 worldNormal;
out vec3 viewNormal;
#endif

void main()
{
  gl_Position = vec4(pos, 1.0, 1.0);
  viewPosition = vec3(pos, -1.0);

#ifndef VOLUMETRICS
  /* Not used in practice but needed to avoid compilation errors. */
  worldPosition = viewPosition;
  worldNormal = viewNormal = normalize(-viewPosition);
#endif

#ifdef USE_ATTR
  pass_attr(viewPosition);
#endif
}