support transparency in material's diffa

panda/src/egg2pg/config_egg2pg.cxx

@@ -184,6 +184,13 @@ ConfigVariableInt egg_vertex_max_num_joints
           "more than this number of joints, the joints with the lesser membership "
           "value are ignored.  Set this to -1 to allow any number of joints."));
 
+ConfigVariableBool egg_implicit_alpha_binary
+("egg-implicit-alpha-binary", false,
+ PRC_DESC("If this is true, then a <Scalar> alpha value appearing in an egg "
+          "file that appears to specify only a binary (0 or 1) value for alpha "
+          "will automatically be downgraded to alpha type \"binary\" instead of "
+          "whatever appears in the egg file."));
+
 ConfigureFn(config_egg2pg) {
   init_libegg2pg();
 }

panda/src/egg2pg/config_egg2pg.h

@@ -54,6 +54,7 @@ extern EXPCL_PANDAEGG ConfigVariableBool egg_emulate_bface;
 extern EXPCL_PANDAEGG ConfigVariableBool egg_preload_simple_textures;
 extern EXPCL_PANDAEGG ConfigVariableDouble egg_vertex_membership_quantize;
 extern EXPCL_PANDAEGG ConfigVariableInt egg_vertex_max_num_joints;
+extern EXPCL_PANDAEGG ConfigVariableBool egg_implicit_alpha_binary;
 
 extern EXPCL_PANDAEGG void init_libegg2pg();
 

panda/src/egg2pg/eggRenderState.cxx

@@ -247,10 +247,15 @@ fill_state(EggPrimitive *egg_prim) {
   }
 
   if (egg_prim->has_material()) {
+    PT(EggMaterial) material = egg_prim->get_material();
     CPT(RenderAttrib) mt =
-      get_material_attrib(egg_prim->get_material(),
-                          egg_prim->get_bface_flag());
+      get_material_attrib(material, egg_prim->get_bface_flag());
     add_attrib(mt);
+
+    if (material->has_diff() && material->get_diff()[3] != 1.0) {
+      implicit_alpha = true;
+      binary_alpha_only = false;
+    }
   }
 
 
@@ -294,11 +299,13 @@ fill_state(EggPrimitive *egg_prim) {
   case EggRenderMode::AM_ms:
   case EggRenderMode::AM_ms_mask:
   case EggRenderMode::AM_dual:
-    // Any of these modes gets implicitly downgraded to AM_binary, if
-    // all of the alpha sources only contribute a binary value to
-    // alpha.
-    if (binary_alpha_only) {
-      am = EggRenderMode::AM_binary;
+    if (egg_implicit_alpha_binary) {
+      // Any of these modes gets implicitly downgraded to AM_binary, if
+      // all of the alpha sources only contribute a binary value to
+      // alpha.
+      if (binary_alpha_only) {
+        am = EggRenderMode::AM_binary;
+      }
     }
     break;