ADD: IBL glsl cleaning

shaders/background_env.frag

@@ -1,21 +1,11 @@
 #version 450
 #extension GL_GOOGLE_include_directive : require
 #include "input_structures.glsl"
+#include "ibl_common.glsl"
 
 layout(location=0) in vec2 inUV;
 layout(location=0) out vec4 outColor;
 
-// IBL specular equirect 2D (LOD 0 for background)
-layout(set=3, binding=0) uniform sampler2D iblSpec2D;
-
-vec2 dir_to_equirect(vec3 d)
-{
-    d = normalize(d);
-    float phi = atan(d.z, d.x);
-    float theta = acos(clamp(d.y, -1.0, 1.0));
-    return vec2(phi * (0.15915494309) + 0.5, theta * (0.31830988618));
-}
-
 void main()
 {
     // Reconstruct world-space direction from screen UV