Initial implementation of the filament rendering backend for mujoco.

This is intended as a drop-in replacement for mjr_render to enable high
quality, physically-based rendering (PBR) using the filament render engine.

This is a work-in-progress and, as such, some features may be missing. This
is also a code-only drop; build files (including instructions on how to
generate the filament materials) will be provided at a later date.

This library is intended to be run with the experimental studio app.

PiperOrigin-RevId: 817593684
Change-Id: Ib9cd14c1881e4897c1111275bd749aa38ebb5317

src/experimental/filament/assets/pbr.mat

@@ -0,0 +1,54 @@
+// 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,
+    shadingModel : lit,
+    culling: none,
+    flipUV: false,
+    parameters : [
+        { type : sampler2d, name : BaseColor },
+        { 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.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/assets/pbr_packed.mat

@@ -0,0 +1,51 @@
+// 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,
+    shadingModel : lit,
+    culling: none,
+    flipUV: false,
+    parameters : [
+        { type : sampler2d, name : BaseColor },
+        { 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.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/phong_2d.mat

@@ -0,0 +1,50 @@
+// 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 : phong_2d,
+    shadingModel : specularGlossiness,
+    culling : none,
+    flipUV : false,
+    parameters : [
+        { type : float4, name : BaseColorFactor },
+        { type : float, name : SpecularFactor },
+        { type : float, name : GlossinessFactor },
+        { type : float, name : EmissiveFactor },
+        { type : float3, name : UvScale },
+        { type : sampler2d, name : BaseColor }
+    ],
+    variables : [
+         vertex_pos
+    ]
+}
+
+vertex {
+  void materialVertex(inout MaterialVertexInputs material) {
+    material.vertex_pos = getPosition();
+  }
+}
+
+fragment {
+  void material(inout MaterialInputs material) {
+    vec2 uv = variable_vertex_pos.xy * materialParams.UvScale.xy;
+
+    prepareMaterial(material);
+    material.baseColor     = materialParams.BaseColorFactor;
+    material.baseColor     *= texture(materialParams_BaseColor, uv);
+    material.specularColor = vec3(materialParams.SpecularFactor);
+    material.glossiness    = materialParams.GlossinessFactor;
+    material.emissive      = vec4(materialParams.EmissiveFactor);
+  }
+}

src/experimental/filament/assets/phong_2d_fade.mat

@@ -0,0 +1,51 @@
+// 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 : phong_2d,
+    shadingModel : specularGlossiness,
+    culling : none,
+    flipUV : false,
+    blending: fade,
+    parameters : [
+        { type : float4, name : BaseColorFactor },
+        { type : float, name : SpecularFactor },
+        { type : float, name : GlossinessFactor },
+        { type : float, name : EmissiveFactor },
+        { type : float3, name : UvScale },
+        { type : sampler2d, name : BaseColor }
+    ],
+    variables : [
+         vertex_pos
+    ]
+}
+
+vertex {
+  void materialVertex(inout MaterialVertexInputs material) {
+    material.vertex_pos = getPosition();
+  }
+}
+
+fragment {
+  void material(inout MaterialInputs material) {
+    vec2 uv = variable_vertex_pos.xy * materialParams.UvScale.xy;
+
+    prepareMaterial(material);
+    material.baseColor     = materialParams.BaseColorFactor;
+    material.baseColor     *= texture(materialParams_BaseColor, uv);
+    material.specularColor = vec3(materialParams.SpecularFactor);
+    material.glossiness    = materialParams.GlossinessFactor;
+    material.emissive      = vec4(materialParams.EmissiveFactor);
+  }
+}

src/experimental/filament/assets/phong_2d_uv.mat

@@ -0,0 +1,43 @@
+// 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 : phong_2d_uv,
+    shadingModel : specularGlossiness,
+    culling : none,
+    flipUV : false,
+    parameters : [
+        { type : float4, name : BaseColorFactor },
+        { type : float, name : SpecularFactor },
+        { type : float, name : GlossinessFactor },
+        { type : float, name : EmissiveFactor },
+        { type : sampler2d, name : BaseColor }
+    ],
+    requires : [
+        uv0
+    ],
+}
+
+fragment {
+  void material(inout MaterialInputs material) {
+    vec2 uv = getUV0();
+
+    prepareMaterial(material);
+    material.baseColor     = materialParams.BaseColorFactor;
+    material.baseColor     *= texture(materialParams_BaseColor, uv);
+    material.specularColor = vec3(materialParams.SpecularFactor);
+    material.glossiness    = materialParams.GlossinessFactor;
+    material.emissive      = vec4(materialParams.EmissiveFactor);
+  }
+}

src/experimental/filament/assets/phong_2d_uv_fade.mat

@@ -0,0 +1,44 @@
+// 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 : phong_2d_uv,
+    shadingModel : specularGlossiness,
+    culling : none,
+    flipUV : false,
+    blending: fade,
+    parameters : [
+        { type : float4, name : BaseColorFactor },
+        { type : float, name : SpecularFactor },
+        { type : float, name : GlossinessFactor },
+        { type : float, name : EmissiveFactor },
+        { type : sampler2d, name : BaseColor }
+    ],
+    requires : [
+        uv0
+    ],
+}
+
+fragment {
+  void material(inout MaterialInputs material) {
+    vec2 uv = getUV0();
+
+    prepareMaterial(material);
+    material.baseColor     = materialParams.BaseColorFactor;
+    material.baseColor     *= texture(materialParams_BaseColor, uv);
+    material.specularColor = vec3(materialParams.SpecularFactor);
+    material.glossiness    = materialParams.GlossinessFactor;
+    material.emissive      = vec4(materialParams.EmissiveFactor);
+  }
+}

src/experimental/filament/assets/phong_color.mat

@@ -0,0 +1,35 @@
+// 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 : phong_color,
+    shadingModel : specularGlossiness,
+    culling: none,
+    parameters : [
+        { type : float4, name : BaseColorFactor },
+        { type : float, name : SpecularFactor },
+        { type : float, name : GlossinessFactor },
+        { type : float, name : EmissiveFactor }
+    ]
+}
+
+fragment {
+  void material(inout MaterialInputs material) {
+    prepareMaterial(material);
+    material.baseColor     = materialParams.BaseColorFactor;
+    material.specularColor = vec3(materialParams.SpecularFactor);
+    material.glossiness    = materialParams.GlossinessFactor;
+    material.emissive      = vec4(materialParams.EmissiveFactor);
+  }
+}

src/experimental/filament/assets/phong_color_fade.mat

@@ -0,0 +1,36 @@
+// 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 : phong_color_fade,
+    shadingModel : specularGlossiness,
+    culling: none,
+    blending: fade,
+    parameters : [
+        { type : float4, name : BaseColorFactor },
+        { type : float, name : SpecularFactor },
+        { type : float, name : GlossinessFactor },
+        { type : float, name : EmissiveFactor }
+    ]
+}
+
+fragment {
+  void material(inout MaterialInputs material) {
+    prepareMaterial(material);
+    material.baseColor     = materialParams.BaseColorFactor;
+    material.specularColor = vec3(materialParams.SpecularFactor);
+    material.glossiness    = materialParams.GlossinessFactor;
+    material.emissive      = vec4(materialParams.EmissiveFactor);
+  }
+}

src/experimental/filament/assets/phong_cube.mat

@@ -0,0 +1,50 @@
+// 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 : phong_cube,
+    shadingModel : specularGlossiness,
+    culling : none,
+    flipUV : false,
+    parameters : [
+        { type : float4, name : BaseColorFactor },
+        { type : float, name : SpecularFactor },
+        { type : float, name : GlossinessFactor },
+        { type : float, name : EmissiveFactor },
+        { type : float3, name : UvScale },
+        { type : samplerCubemap, name : BaseColor }
+    ],
+    variables : [
+         vertex_pos
+    ]
+}
+
+vertex {
+  void materialVertex(inout MaterialVertexInputs material) {
+    material.vertex_pos = getPosition();
+  }
+}
+
+fragment {
+  void material(inout MaterialInputs material) {
+    vec3 uv = variable_vertex_pos.xyz * materialParams.UvScale;
+
+    prepareMaterial(material);
+    material.baseColor     = materialParams.BaseColorFactor;
+    material.baseColor     *= texture(materialParams_BaseColor, uv);
+    material.specularColor = vec3(materialParams.SpecularFactor);
+    material.glossiness    = materialParams.GlossinessFactor;
+    material.emissive      = vec4(materialParams.EmissiveFactor);
+  }
+}

src/experimental/filament/assets/phong_cube_fade.mat

@@ -0,0 +1,51 @@
+// 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 : phong_cube,
+    shadingModel : specularGlossiness,
+    culling : none,
+    flipUV : false,
+    blending: fade,
+    parameters : [
+        { type : float4, name : BaseColorFactor },
+        { type : float, name : SpecularFactor },
+        { type : float, name : GlossinessFactor },
+        { type : float, name : EmissiveFactor },
+        { type : float3, name : UvScale },
+        { type : samplerCubemap, name : BaseColor }
+    ],
+    variables : [
+         vertex_pos
+    ]
+}
+
+vertex {
+  void materialVertex(inout MaterialVertexInputs material) {
+    material.vertex_pos = getPosition();
+  }
+}
+
+fragment {
+  void material(inout MaterialInputs material) {
+    vec3 uv = variable_vertex_pos.xyz * materialParams.UvScale;
+
+    prepareMaterial(material);
+    material.baseColor     = materialParams.BaseColorFactor;
+    material.baseColor     *= texture(materialParams_BaseColor, uv);
+    material.specularColor = vec3(materialParams.SpecularFactor);
+    material.glossiness    = materialParams.GlossinessFactor;
+    material.emissive      = vec4(materialParams.EmissiveFactor);
+  }
+}

src/experimental/filament/assets/unlit_depth.mat

@@ -0,0 +1,31 @@
+// 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 : unlit_depth,
+    shadingModel : unlit,
+    blending : opaque,
+    culling: none,
+    depthWrite: true
+}
+
+fragment {
+  void material(inout MaterialInputs material) {
+    prepareMaterial(material);
+    float3 worldPosition = getWorldPosition();
+    float4 clipPosition = mulMat4x4Float3(getClipFromWorldMatrix(), worldPosition);
+    float3 normalizedPosition = clipPosition.xyz / clipPosition.w;
+    material.baseColor.rgb = vec3(normalizedPosition.z);
+  }
+}

src/experimental/filament/assets/unlit_segmentation.mat

@@ -0,0 +1,29 @@
+// 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 : unlit_segmentation,
+    shadingModel : unlit,
+    culling: none,
+    parameters : [
+        { type : float4, name : BaseColorFactor }
+    ]
+}
+
+fragment {
+    void material(inout MaterialInputs material) {
+      prepareMaterial(material);
+      material.baseColor = materialParams.BaseColorFactor;
+    }
+}

src/experimental/filament/assets/unlit_ui.mat

@@ -0,0 +1,43 @@
+// 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 : unlit_ui,
+    parameters : [
+        {
+            type : sampler2d,
+            name : glyph
+        }
+    ],
+    requires : [
+        uv0,
+        color
+    ],
+    shadingModel : unlit,
+    culling : none,
+    depthCulling: false,
+    blending : transparent,
+    featureLevel : 0
+}
+
+fragment {
+    void material(inout MaterialInputs material) {
+        prepareMaterial(material);
+        vec2 uv = getUV0();
+        uv.y = 1.0 - uv.y;
+        vec4 tex_color = texture2D(materialParams_glyph, uv);
+        material.baseColor = getColor() * tex_color;
+        material.baseColor.rgb *= material.baseColor.a;
+    }
+}