Alphamasking migrated to shaders instead of using fixed-function. Very early code. Hasn't even made it into viewer-development yet.

indra/newview/app_settings/shaders/class1/objects/impostorF.glsl

@@ -0,0 +1,26 @@
+/** 
+ * @file impostorF.glsl
+ *
+ * $LicenseInfo:firstyear=2007&license=viewerlgpl$
+ * $/LicenseInfo$
+ */
+ 
+uniform float minimum_alpha;
+uniform float maximum_alpha;
+
+vec3 fullbrightAtmosTransport(vec3 light);
+vec3 fullbrightScaleSoftClip(vec3 light);
+
+uniform sampler2D diffuseMap;
+
+void main()
+{
+	vec4 color = texture2D(diffuseMap,gl_TexCoord[0].xy) * gl_Color;
+	
+	if (color.a < minimum_alpha || color.a > maximum_alpha)
+	{
+		discard;
+	}
+
+	gl_FragColor = color;
+}