#3059 Fix for PBR hair fighting itself (and other fully transparent materials) (#3080)

Author: Geenz

indra/newview/llvovolume.cpp

@@ -5925,7 +5925,24 @@ void LLVolumeGeometryManager::rebuildGeom(LLSpatialGroup* group)
                             {
                                 if (gltf_mat != nullptr)
                                 {
-                                    add_face(sPbrFaces, pbr_count, facep);
+                                    // In theory, we should never actually get here with alpha blending.
+                                    // How this is supposed to work is we check if the surface is alpha blended, and we assign it to the alpha draw pool.
+                                    // For rigged meshes, this apparently may not happen consistently.
+                                    // For now, just discard it here if the alpha is 0 (fully transparent) to achieve parity with blinn-phong materials in function.
+
+                                    bool should_render = true;
+                                    if (gltf_mat->mAlphaMode == LLGLTFMaterial::ALPHA_MODE_BLEND)
+                                    {
+                                        if (gltf_mat->mBaseColor.mV[3] == 0.0f)
+                                        {
+                                            should_render = false;
+                                        }
+                                    }
+
+                                    if (should_render)
+                                    {
+                                        add_face(sPbrFaces, pbr_count, facep);
+                                    }
                                 }
                                 else
                                 {