diff --git a/zenovis/xinxinoptix/DeflMatShader.cu b/zenovis/xinxinoptix/DeflMatShader.cu
index 8a9f79413d..f765674a32 100644
--- a/zenovis/xinxinoptix/DeflMatShader.cu
+++ b/zenovis/xinxinoptix/DeflMatShader.cu
@@ -184,14 +184,6 @@ static __inline__ __device__ bool isBadVector(float3& vector) {
     return isBadVector(tmp);
 }
 
-static __inline__ __device__ float3 sphereUV(float3 &direction) {
-    
-    return float3 {
-        atan2(direction.x, direction.z) / (2.0f*M_PIf) + 0.5f,
-        direction.y * 0.5f + 0.5f, 0.0f
-    };
-} 
-
 extern "C" __global__ void __anyhit__shadow_cutout()
 {
 
@@ -234,7 +226,7 @@ extern "C" __global__ void __anyhit__shadow_cutout()
 
     attrs.pos = P;
     attrs.nrm = N;
-    attrs.uv = sphereUV(_normal_object_);
+    attrs.uv = sphereUV(_normal_object_, false);
 
     attrs.clr = {};
     attrs.tang = {};
@@ -505,7 +497,7 @@ extern "C" __global__ void __closesthit__radiance()
 
     attrs.pos = P;
     attrs.nrm = N;
-    attrs.uv = sphereUV(_normal_object_);
+    attrs.uv = sphereUV(_normal_object_, false);
 
     attrs.clr = {};
     attrs.tang = {};
diff --git a/zenovis/xinxinoptix/Light.cu b/zenovis/xinxinoptix/Light.cu
index 4e1b542789..edbf61c832 100644
--- a/zenovis/xinxinoptix/Light.cu
+++ b/zenovis/xinxinoptix/Light.cu
@@ -21,14 +21,6 @@ static __inline__ __device__ void evalSurface(float4* uniforms) {
     //GENERATED_BEGIN_MARK
 
     //GENERATED_END_MARK
-}
-
-static __inline__ __device__ float3 sphereUV(float3 &direction) {
-    
-    return float3 {
-        atan2(direction.x, direction.z) / (2.0f*M_PIf) + 0.5f,
-        direction.y * 0.5f + 0.5f, 0.0f
-    };
 } 
 
 static __inline__ __device__ bool checkLightGAS(uint instanceId) {
diff --git a/zenovis/xinxinoptix/Sampling.h b/zenovis/xinxinoptix/Sampling.h
index 76358988a7..33eb6ca7d7 100644
--- a/zenovis/xinxinoptix/Sampling.h
+++ b/zenovis/xinxinoptix/Sampling.h
@@ -137,6 +137,17 @@ namespace rtgems {
     }
 }
 
+static __host__ __device__ __inline__ float3 sphereUV(const float3 &dir, bool internal) {
+//https://en.wikipedia.org/wiki/UV_mapping
+
+    auto x = internal? dir.x:-dir.x;
+
+    auto u = 0.5f + atan2f(dir.z, x) * 0.5f / M_PIf;
+    auto v = 0.5f + asinf(dir.y) / M_PIf;
+
+    return float3 {u, v, 0.0f};
+} 
+
 // *Really* minimal PCG32 code / (c) 2014 M.E. O'Neill / pcg-random.org
 // Licensed under Apache License 2.0 (NO WARRANTY, etc. see website)
 
diff --git a/zenovis/xinxinoptix/proceduralSky.h b/zenovis/xinxinoptix/proceduralSky.h
index 80e5b6395f..47dd61b9f2 100644
--- a/zenovis/xinxinoptix/proceduralSky.h
+++ b/zenovis/xinxinoptix/proceduralSky.h
@@ -1,4 +1,5 @@
 #pragma once
+#include "Sampling.h"
 #include "zxxglslvec.h"
 #include "TraceStuff.h"
 
@@ -304,8 +305,8 @@ static __inline__ __device__ vec3 hdrSky2(
             .rotX(to_radians(params.sky_rot_x))
             .rotZ(to_radians(params.sky_rot_z))
             .rotY(to_radians(params.sky_rot));
-  float u = atan2(dir.z, dir.x)  / 3.1415926f * 0.5f + 0.5f;
-  float v = asin(dir.y) / 3.1415926f + 0.5f;
+            
+  vec3 uv = sphereUV(dir, true);
   vec3 col = vec3(0);
   for(int jj=-2;jj<=2;jj++)
   {
@@ -313,7 +314,7 @@ static __inline__ __device__ vec3 hdrSky2(
     {
       float dx = (float)ii / (float)(params.skynx);
       float dy = (float)jj / (float)(params.skyny);
-      col = col + (vec3)texture2D(params.sky_texture, vec2(u + dx, v + dy)) * params.sky_strength;
+      col = col + (vec3)texture2D(params.sky_texture, vec2(uv[0] + dx, uv[1] + dy)) * params.sky_strength;
     }
   }
 
@@ -328,12 +329,13 @@ static __inline__ __device__ vec3 hdrSky(
             .rotX(to_radians(params.sky_rot_x))
             .rotZ(to_radians(params.sky_rot_z))
             .rotY(to_radians(params.sky_rot));
-    float u = atan2(dir.z, dir.x)  / 3.1415926f * 0.5f + 0.5f;
-    float v = asin(dir.y) / 3.1415926f + 0.5f;
-    vec3 col = (vec3)texture2D(params.sky_texture, vec2(u, v)) * params.sky_strength;
+
+    vec3 uv = sphereUV(dir, true);
+
+    vec3 col = (vec3)texture2D(params.sky_texture, vec2(uv[0], uv[1])) * params.sky_strength;
     vec3 col2 = clamp(col, vec3(0.0f), vec3(upperBound));
-    int i = u * params.skynx;
-    int j = v * params.skyny;
+    int i = uv[0] * params.skynx;
+    int j = uv[1] * params.skyny;
     //float p = params.skycdf[params.skynx * params.skyny + j * params.skynx + i];
     pdf = luminance(col) / params.envavg / (2.0f * M_PIf * M_PIf);
     return mix(col, col2, isclamp);