diff --git a/shader/sky/fog.frag b/shader/sky/fog.frag
index cc2677883..a45392e85 100644
--- a/shader/sky/fog.frag
+++ b/shader/sky/fog.frag
@@ -51,6 +51,10 @@ layout(binding = 4) uniform utexture3D pageTbl;
 layout(binding = 5) uniform texture2D  pageData;
 #endif
 
+const float dFogMin = 0;
+//const float dFogMax = 1;
+const float dFogMax = 0.9999;
+
 #if defined(GL_COMPUTE_SHADER)
 uvec2 invocationID = gl_GlobalInvocationID.xy;
 #endif
@@ -175,10 +179,8 @@ vec4 fog(vec2 uv, float z) {
   const int   steps    = 32;
   const float noise    = interleavedGradientNoise()/steps;
 
-  const float dMin     = 0;
-  const float dMax     = 0.9999;
-  const vec3  pos0     = project(scene.viewProjectLwcInv, vec3(inPos,dMin));
-  const vec3  pos1     = project(scene.viewProjectLwcInv, vec3(inPos,dMax));
+  const vec3  pos0     = project(scene.viewProjectLwcInv, vec3(inPos,dFogMin));
+  const vec3  pos1     = project(scene.viewProjectLwcInv, vec3(inPos,dFogMax));
   const vec3  posz     = project(scene.viewProjectLwcInv, vec3(inPos,z));
 
 #if defined(VIRTUAL_SHADOW) || defined(VIRTUAL_SHADOW_MARK)
@@ -262,11 +264,9 @@ const vec3 debugColors[MAX_DEBUG_COLORS] = {
   };
 
 vec4 fog(vec2 uv, float z) {
-  float dMin = 0;
-  float dMax = 0.9999;
-  float dZ   = linearDepth(   z, scene.clipInfo);
-  float d0   = linearDepth(dMin, scene.clipInfo);
-  float d1   = linearDepth(dMax, scene.clipInfo);
+  float dZ   = linearDepth(      z, scene.clipInfo);
+  float d0   = linearDepth(dFogMin, scene.clipInfo);
+  float d1   = linearDepth(dFogMax, scene.clipInfo);
   float d    = (dZ-d0)/(d1-d0);
   // return vec4(debugColors[min(int(d*textureSize(fogLut,0).z), textureSize(fogLut,0).z-1)%MAX_DEBUG_COLORS], 0);
   return textureLod(fogLut, vec3(uv,d), 0);
diff --git a/shader/virtual_shadow/vsm_common.glsl b/shader/virtual_shadow/vsm_common.glsl
index 2ec1216ec..f5bfb8245 100644
--- a/shader/virtual_shadow/vsm_common.glsl
+++ b/shader/virtual_shadow/vsm_common.glsl
@@ -64,15 +64,19 @@ bool vsmPageClip(ivec2 fragCoord, const uint page) {
   }
 
 int vsmCalcMipIndex(in vec2 shPos) {
+#if 1
+  float d  = max(abs(shPos.x), abs(shPos.y));
+  uint  id = uint(d);
+  return findMSB(id)+1;
+#else
   float x = ceil(log2(max(abs(shPos.x), 1)));
   float y = ceil(log2(max(abs(shPos.y), 1)));
   return int(max(x,y));
+#endif
   }
 
 int vsmCalcMipIndex(in vec2 shPos, int minMip) {
-  float x = ceil(log2(max(abs(shPos.x), 1)));
-  float y = ceil(log2(max(abs(shPos.y), 1)));
-  return max(minMip, int(max(x,y)));
+  return max(vsmCalcMipIndex(shPos), minMip);
   }
 
 uint pageIdHash7(ivec3 src) {