skybox_blit_frag.glsl

#version 300 es

precision highp float;

uniform vec3 u_camera;
in vec3 v_pos;
uniform sampler2D u_skybox_tex;
uniform highp sampler3D cloud_base_texture;

out vec4 fragColor;

#define PI 3.14159
vec2 dir_to_skybox_uv(vec3 dir) {
  vec2 uv = vec2(atan(dir.x, -dir.z), acos(dir.y));
  if (uv.x < 0.0) {
    uv.x += PI * 2.0;
  }
  return (uv / vec2(PI * 2.0, PI));
}
vec3 skybox_uv_to_dir(vec2 uv) {
	uv = (uv - 0.5) * vec2(-2.0, -1.0) * PI;
	vec3 r_dir = normalize( vec3( sin(uv.x), tan(uv.y), cos(uv.x) ) * cos(uv.y) );
	return r_dir;
}

void main() {
  vec3 rayDir = normalize(v_pos - u_camera);
  vec2 uv = dir_to_skybox_uv(rayDir);
  fragColor = texture(u_skybox_tex, uv);
  // fragColor = vec4(texture(cloud_base_texture, vec3(uv, 0.5)).z * 100000000000.0);
  // fragColor = vec4(texture(cloud_base_texture, vec3(rayDir * 50.0)).rgb * 10000.0, 1.0);
}