1 files changed, 6 insertions, 7 deletions
diff --git a/indra/newview/app_settings/shaders/class1/deferred/materialF.glsl b/indra/newview/app_settings/shaders/class1/deferred/materialF.glsl
index b26194f278..b30d7655db 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/materialF.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/materialF.glsl
@@ -202,7 +202,7 @@ VARYING vec2 vary_texcoord2;
 uniform float env_intensity;
 uniform vec4 specular_color;  // specular color RGB and specular exponent (glossiness) in alpha
 
-#ifdef HAS_ALPHA_MASK
+#if (DIFFUSE_ALPHA_MODE == DIFFUSE_ALPHA_MODE_MASK)
 uniform float minimum_alpha;
 #endif
 
@@ -227,12 +227,11 @@ void main()
     vec4 diffcol = texture2D(diffuseMap, vary_texcoord0.xy);
 	diffcol.rgb *= vertex_color.rgb;
 
-#ifdef HAS_ALPHA_MASK
-#if DIFFUSE_ALPHA_MODE == DIFFUSE_ALPHA_MODE_BLEND
-    if (diffcol.a*vertex_color.a < minimum_alpha)
-#else
-    if (diffcol.a < minimum_alpha)
-#endif
+#if (DIFFUSE_ALPHA_MODE == DIFFUSE_ALPHA_MODE_MASK)
+
+    // Comparing floats cast from 8-bit values, produces acne right at the 8-bit transition points
+    float bias = 0.001953125; // 1/512, or half an 8-bit quantization (SL-18637)
+    if (diffcol.a < minimum_alpha-bias)
     {
         discard;
     }