diff --git a/include/common/bspfile.hh b/include/common/bspfile.hh
index 9213235d..def1f39b 100644
--- a/include/common/bspfile.hh
+++ b/include/common/bspfile.hh
@@ -355,6 +355,8 @@ typedef struct {
 #define TEX_NOMINLIGHT (1ULL << 54)   /* opt out of minlight on this face */
 #define TEX_NOEXPAND  (1ULL << 55)   /* don't expand this face for larger clip hulls */
 #define TEX_LIGHTIGNORE (1ULL << 56)
+#define TEX_LIGHT_ALPHA_SHIFT 57
+#define TEX_LIGHT_ALPHA_MASK  (127ULL << TEX_LIGHT_ALPHA_SHIFT) /* 7 bit unsigned value. custom opacity */
 
 // Q2 Texture flags.
 #define    Q2_SURF_LIGHT      0x1        // value will hold the light strength
diff --git a/include/qbsp/qbsp.hh b/include/qbsp/qbsp.hh
index 001e99fc..eff7c070 100644
--- a/include/qbsp/qbsp.hh
+++ b/include/qbsp/qbsp.hh
@@ -144,7 +144,8 @@
 #define TEX_NOMINLIGHT (1ULL << 54)   /* opt out of minlight on this face */
 #define TEX_NOEXPAND  (1ULL << 55)   /* don't expand this face for larger clip hulls */
 #define TEX_LIGHTIGNORE (1ULL << 56)
-
+#define TEX_LIGHT_ALPHA_SHIFT 57
+#define TEX_LIGHT_ALPHA_MASK  (127ULL << TEX_LIGHT_ALPHA_SHIFT) /* 7 bit unsigned value. custom opacity */
 /*
  * The quality of the bsp output is highly sensitive to these epsilon values.
  * Notes:
diff --git a/light/trace_embree.cc b/light/trace_embree.cc
index eb138cce..bfd234ca 100644
--- a/light/trace_embree.cc
+++ b/light/trace_embree.cc
@@ -301,9 +301,7 @@ Embree_FilterFuncN(int* valid,
         
         // test fence textures and glass
         const bsp2_dface_t *face = Embree_LookupFace(geomID, primID);
-        
-        
-        float alpha = hit_modelinfo->alpha.floatValue();
+        float alpha = Face_Alpha(hit_modelinfo, face);
 
         //mxd
         bool isFence, isGlass;
@@ -561,6 +559,26 @@ MakeFaces(const mbsp_t *bsp, const dmodel_t *model)
     return result;
 }
 
+/**
+ * Returns 1.0 unless a custom alpha value is set.
+ * The priority is: "_light_alpha" (read from extended_texinfo_flags), then "alpha"
+ */
+static float
+Face_Alpha(const modelinfo_t *modelinfo, const bsp2_dface_t *face)
+{
+    const uint64_t extended_flags = extended_texinfo_flags[face->texinfo];  
+
+    // for _light_alpha, 0 is considered unset
+    const uint64_t alpha_u7 = (extended_flags >> TEX_LIGHT_ALPHA_SHIFT) & 127ULL;
+    const float alpha_float = (float)alpha_u7 / (float)127;
+    if (alpha_float != 0.0f) {
+        return alpha_float;
+    }
+
+    // next check modelinfo alpha (defaults to 1.0)
+    return modelinfo->alpha.floatValue();
+}
+
 void
 Embree_TraceInit(const mbsp_t *bsp)
 {
@@ -602,8 +620,9 @@ Embree_TraceInit(const mbsp_t *bsp)
             if(bsp->loadversion == Q2_BSPVERSION && (contents & Q2_SURF_NODRAW) && !(contents & Q2_SURF_SKY))
                 continue;
             
-            // handle glass
-            if (model->alpha.floatValue() < 1.0f 
+            // handle glass / water 
+            const float alpha = Face_Alpha(model, face);
+            if (alpha < 1.0f
                 || (bsp->loadversion == Q2_BSPVERSION && (contents & Q2_SURF_TRANSLUCENT))) { //mxd. Both fence and transparent textures are done using SURF_TRANS flags in Q2
                 filterfaces.push_back(face);
                 continue;
diff --git a/qbsp/map.cc b/qbsp/map.cc
index dad8ab08..1401f6ed 100644
--- a/qbsp/map.cc
+++ b/qbsp/map.cc
@@ -359,7 +359,7 @@ FindTexinfoEnt(mtexinfo_t *texinfo, const mapentity_t *entity)
     // handle "_minlight"
     const vec_t minlight = atof(ValueForKey(entity, "_minlight"));
     if (minlight > 0) {
-        const uint8_t minlight_byte = (uint8_t) qmax(0, qmin(255, (int)rint(minlight)));
+        const uint64_t minlight_byte = (uint64_t) qmax(0, qmin(255, (int)rint(minlight)));
         flags |= (minlight_byte << TEX_MINLIGHT_SHIFT);
     }
 
@@ -383,6 +383,14 @@ FindTexinfoEnt(mtexinfo_t *texinfo, const mapentity_t *entity)
             flags |= (b_byte << TEX_MINLIGHT_COLOR_B_SHIFT);
         }
     }
+
+    // handle "_light_alpha"
+    const vec_t lightalpha = atof(ValueForKey(entity, "_light_alpha"));
+    if (lightalpha != 0.0) {
+        const uint64_t lightalpha_u7 = (uint64_t) qmax(0, qmin(127, (int)rint(lightalpha * 127.0)));
+        Q_assert(lightalpha_u7 < 128u);
+        flags |= (lightalpha_u7 << TEX_LIGHT_ALPHA_SHIFT);
+    }
     
     return FindTexinfo(texinfo, flags);
 }