Add support for transparent PBR materials.

PiperOrigin-RevId: 919477028
Change-Id: I75cc311fc73dd5fe26b72ba8d49fd421fda455e3

src/experimental/filament/CMakeLists.txt

@@ -100,7 +100,9 @@ file(COPY
 set(MATC_EXECUTABLE matc)
 set(MATERIAL_FILES
     pbr.mat
+    pbr_transparent.mat
     pbr_packed.mat
+    pbr_packed_transparent.mat
     phong_2d_fade.mat
     phong_2d.mat
     phong_2d_reflect.mat

src/experimental/filament/assets/pbr_packed_transparent.mat

@@ -0,0 +1,53 @@
+// Copyright 2025 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+material {
+    name : pbr_packed_transparent,
+    shadingModel : lit,
+    flipUV: false,
+    blending: transparent,
+    parameters : [
+        { type : sampler2d, name : BaseColor },
+        { type : sampler2d, name : Opacity },
+        { type : sampler2d, name : Normal },
+        { type : sampler2d, name : ORM },
+        { type : sampler2d, name : Emissive },
+        { type : float4, name : BaseColorFactor },
+        { type : float, name : MetallicFactor },
+        { type : float, name : RoughnessFactor }
+    ],
+    requires : [
+        uv0
+    ]
+}
+
+fragment {
+  void material(inout MaterialInputs material) {
+    vec2 uv = getUV0();
+
+    material.normal = texture(materialParams_Normal, uv).xyz * 2.0 - 1.0;
+    prepareMaterial(material);
+
+    material.baseColor        = materialParams.BaseColorFactor;
+    material.baseColor        *= texture(materialParams_BaseColor, uv);
+    material.baseColor.a      *= texture(materialParams_Opacity, uv).r;
+    material.ambientOcclusion = texture(materialParams_ORM, uv).r;
+    material.roughness        = materialParams.RoughnessFactor;
+    material.roughness        *= texture(materialParams_ORM, uv).g;
+    material.metallic         = materialParams.MetallicFactor;
+    material.metallic         *= texture(materialParams_ORM, uv).b;
+    material.emissive         = texture(materialParams_Emissive, uv);
+    material.emissive.a       = 1.0 - material.emissive.a;
+  }
+}

src/experimental/filament/assets/pbr_transparent.mat

@@ -0,0 +1,56 @@
+// Copyright 2025 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+material {
+    name : pbr_transparent,
+    shadingModel : lit,
+    flipUV: false,
+    blending: transparent,
+    parameters : [
+        { type : sampler2d, name : BaseColor },
+        { type : sampler2d, name : Opacity },
+        { type : sampler2d, name : Normal },
+        { type : sampler2d, name : Occlusion },
+        { type : sampler2d, name : Roughness },
+        { type : sampler2d, name : Metallic },
+        { type : sampler2d, name : Emissive },
+        { type : float4, name : BaseColorFactor },
+        { type : float, name : MetallicFactor },
+        { type : float, name : RoughnessFactor }
+
+    ],
+    requires : [
+        uv0
+    ]
+}
+
+fragment {
+  void material(inout MaterialInputs material) {
+    vec2 uv = getUV0();
+
+    material.normal = texture(materialParams_Normal, uv).xyz * 2.0 - 1.0;
+    prepareMaterial(material);
+
+    material.baseColor        = materialParams.BaseColorFactor;
+    material.baseColor        *= texture(materialParams_BaseColor, uv);
+    material.baseColor.a      *= texture(materialParams_Opacity, uv).r;
+    material.ambientOcclusion = texture(materialParams_Occlusion, uv).r;
+    material.roughness        = materialParams.RoughnessFactor;
+    material.roughness        *= texture(materialParams_Roughness, uv).r;
+    material.metallic         = materialParams.MetallicFactor;
+    material.metallic         *= texture(materialParams_Metallic, uv).r;
+    material.emissive         = texture(materialParams_Emissive, uv);
+    material.emissive.a       = 1.0 - material.emissive.a;
+  }
+}

src/experimental/filament/compat/scene_geom_util.cc

@@ -198,6 +198,7 @@ static void UpdateGeomMaterial(mjrRenderable* renderable, const mjvGeom& geom,
     };
     material.color_texture = get_texture(mjTEXROLE_RGB);
     material.normal_texture = get_texture(mjTEXROLE_NORMAL);
+    material.opacity_texture = get_texture(mjTEXROLE_OPACITY);
     material.emissive_texture = get_texture(mjTEXROLE_EMISSIVE);
     material.orm_texture = get_texture(mjTEXROLE_ORM);
     material.metallic_texture = get_texture(mjTEXROLE_METALLIC);

src/experimental/filament/filament/material.cc

@@ -38,15 +38,35 @@ ObjectManager::MaterialType GetMaterialType(const mjrMaterial& material,
       return ObjectManager::kUnlitDecor;
     }
   } else if (material.orm_texture) {
-    return ObjectManager::kPbrPacked;
+    if (material.opacity_texture) {
+      return ObjectManager::kPbrPackedTransparent;
+    } else {
+      return ObjectManager::kPbrPacked;
+    }
   } else if (material.metallic_texture) {
-    return ObjectManager::kPbr;
+    if (material.opacity_texture) {
+      return ObjectManager::kPbrPackedTransparent;
+    } else {
+      return ObjectManager::kPbr;
+    }
   } else if (material.roughness_texture) {
-    return ObjectManager::kPbr;
+    if (material.color[3] < 1.0f) {
+      return ObjectManager::kPbrTransparent;
+    } else {
+      return ObjectManager::kPbr;
+    }
   } else if (material.metallic >= 0) {
-    return ObjectManager::kPbr;
+    if (material.color[3] < 1.0f) {
+      return ObjectManager::kPbrTransparent;
+    } else {
+      return ObjectManager::kPbr;
+    }
   } else if (material.roughness >= 0) {
-    return ObjectManager::kPbr;
+    if (material.color[3] < 1.0f) {
+      return ObjectManager::kPbrTransparent;
+    } else {
+      return ObjectManager::kPbr;
+    }
   }
 
   // Check to see if we're dealing with a mesh with texture coordinates.
@@ -163,6 +183,7 @@ void UpdateMaterialInstance(filament::MaterialInstance* instance,
   };
 
   TrySetTexture("BaseColor", material.color_texture, mjTEXROLE_RGB);
+  TrySetTexture("Opacity", material.opacity_texture, mjTEXROLE_OPACITY);
   TrySetTexture("Normal", material.normal_texture, mjTEXROLE_NORMAL);
   TrySetTexture("Metallic", material.metallic_texture, mjTEXROLE_METALLIC);
   TrySetTexture("Roughness", material.roughness_texture, mjTEXROLE_ROUGHNESS);

src/experimental/filament/filament/object_manager.cc

@@ -55,6 +55,8 @@ ObjectManager::ObjectManager(filament::Engine* engine)
     : engine_(engine) {
   materials_[kPbr] = LoadMaterial(engine, "pbr.filamat");
   materials_[kPbrPacked] = LoadMaterial(engine, "pbr_packed.filamat");
+  materials_[kPbrTransparent] = LoadMaterial(engine, "pbr_transparent.filamat");
+  materials_[kPbrPackedTransparent] = LoadMaterial(engine, "pbr_packed_transparent.filamat");
   materials_[kPhong2d] = LoadMaterial(engine, "phong_2d.filamat");
   materials_[kPhong2dFade] = LoadMaterial(engine, "phong_2d_fade.filamat");
   materials_[kPhong2dReflect] = LoadMaterial(engine, "phong_2d_reflect.filamat");
@@ -97,6 +99,7 @@ ObjectManager::ObjectManager(filament::Engine* engine)
 
   fallback_textures_[mjTEXROLE_USER] = fallback_black_;
   fallback_textures_[mjTEXROLE_RGB] = fallback_white_;
+  fallback_textures_[mjTEXROLE_OPACITY] = fallback_white_;
   fallback_textures_[mjTEXROLE_OCCLUSION] = fallback_white_;
   fallback_textures_[mjTEXROLE_ROUGHNESS] = fallback_white_;
   fallback_textures_[mjTEXROLE_METALLIC] = fallback_black_;

src/experimental/filament/filament/object_manager.h

@@ -42,7 +42,9 @@ class ObjectManager {
   // ObjectManager.
   enum MaterialType {
     kPbr,
+    kPbrTransparent,
     kPbrPacked,
+    kPbrPackedTransparent,
     kPhong2d,
     kPhong2dFade,
     kPhong2dReflect,

src/experimental/filament/render_context_filament.h

@@ -627,6 +627,9 @@ struct mjrMaterial {
   // The texture containing the base color of the object.
   const mjrTexture* color_texture;
 
+  // The texture containing the opacity of the object.
+  const mjrTexture* opacity_texture;
+
   // The normal map of the object.
   const mjrTexture* normal_texture;
 

src/experimental/studio/live.js

@@ -57,7 +57,9 @@ var Module = {
       "assets/ibl.ktx",
       "assets/OpenSans-Regular.ttf",
       "assets/pbr.filamat",
+      "assets/pbr_transparent.filamat",
       "assets/pbr_packed.filamat",
+      "assets/pbr_packed_transparent.filamat",
       "assets/phong_2d_fade.filamat",
       "assets/phong_2d.filamat",
       "assets/phong_2d_reflect.filamat",