From 8e5436c3354eb5fee5eba3d4b1f7f2c38eba3d34 Mon Sep 17 00:00:00 2001
From: Haroon Qureshi <haroonq@google.com>
Date: Thu, 12 Feb 2026 01:06:45 -0800
Subject: [PATCH] Make phong-shading multipliers configurable.

PiperOrigin-RevId: 869080920
Change-Id: I4eb7311b54270d596c09a01d6725c1efb931de4b
---
 src/experimental/filament/filament/material.cc  | 17 ++++++-----------
 .../filament/filament/object_manager.cc         |  7 +++++++
 .../filament/filament/object_manager.h          |  7 +++++++
 3 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/src/experimental/filament/filament/material.cc b/src/experimental/filament/filament/material.cc
index edf205ca..c62733b9 100644
--- a/src/experimental/filament/filament/material.cc
+++ b/src/experimental/filament/filament/material.cc
@@ -24,11 +24,6 @@
 
 namespace mujoco {
 
-// Various tweakable parameters for mapping mujoco values onto filament.
-static constexpr float kSpecularMultiplier = 0.6f;
-static constexpr float kShininessMultiplier = 0.1f;
-static constexpr float kEmissiveMultiplier = 0.3f;
-
 Material::Material(ObjectManager* object_mgr) : object_mgr_(object_mgr) {
   instances_[kDepth] =
       object_mgr->GetMaterial(ObjectManager::kUnlitDepth)->createInstance();
@@ -88,16 +83,16 @@ void Material::UpdateMaterialInstances() {
                            params_.color);
   }
   if (material->hasParameter("EmissiveFactor")) {
-    instance->setParameter("EmissiveFactor",
-                           params_.emissive * kEmissiveMultiplier);
+    const float multiplier = object_mgr_->GetEmissiveMultiplier();
+    instance->setParameter("EmissiveFactor", params_.emissive * multiplier);
   }
   if (material->hasParameter("SpecularFactor")) {
-    instance->setParameter("SpecularFactor",
-                           params_.specular * kSpecularMultiplier);
+    const float multiplier = object_mgr_->GetSpecularMultiplier();
+    instance->setParameter("SpecularFactor", params_.specular * multiplier);
   }
   if (material->hasParameter("GlossinessFactor")) {
-    instance->setParameter("GlossinessFactor",
-                           params_.glossiness * kShininessMultiplier);
+    const float multiplier = object_mgr_->GetShininessMultiplier();
+    instance->setParameter("GlossinessFactor", params_.glossiness * multiplier);
   }
   if (material->hasParameter("MetallicFactor")) {
     instance->setParameter("MetallicFactor",
diff --git a/src/experimental/filament/filament/object_manager.cc b/src/experimental/filament/filament/object_manager.cc
index 20443c25..28eee711 100644
--- a/src/experimental/filament/filament/object_manager.cc
+++ b/src/experimental/filament/filament/object_manager.cc
@@ -129,6 +129,13 @@ ObjectManager::ObjectManager(const mjModel* model, filament::Engine* engine,
   fallback_textures_[mjTEXROLE_ORM] = fallback_orm_;
 
   fallback_indirect_light_ = LoadFallbackIndirectLight("ibl.ktx", 1.0f);
+
+  specular_multiplier_ = ReadElement(
+      model_, "filament.phong.specular_multiplier", specular_multiplier_);
+  shininess_multiplier_ = ReadElement(
+      model_, "filament.phong.shininess_multiplier", shininess_multiplier_);
+  emissive_multiplier_ = ReadElement(
+      model_, "filament.phong.emissive_multiplier", emissive_multiplier_);
 }
 
 ObjectManager::~ObjectManager() {
diff --git a/src/experimental/filament/filament/object_manager.h b/src/experimental/filament/filament/object_manager.h
index a9aaf4d1..fd37f526 100644
--- a/src/experimental/filament/filament/object_manager.h
+++ b/src/experimental/filament/filament/object_manager.h
@@ -104,6 +104,10 @@ class ObjectManager {
   filament::IndirectLight* LoadFallbackIndirectLight(std::string_view filename,
                                                      float intensity);
 
+  float GetSpecularMultiplier() const { return specular_multiplier_; }
+  float GetShininessMultiplier() const { return shininess_multiplier_; }
+  float GetEmissiveMultiplier() const { return emissive_multiplier_; }
+
   const mjModel* GetModel() const { return model_; }
 
   ObjectManager(const ObjectManager&) = delete;
@@ -129,6 +133,9 @@ class ObjectManager {
   filament::Texture* fallback_normal_ = nullptr;
   filament::Texture* fallback_orm_ = nullptr;
   filament::IndirectLight* fallback_indirect_light_ = nullptr;
+  float specular_multiplier_ = 0.6f;
+  float shininess_multiplier_ = 0.1f;
+  float emissive_multiplier_ = 0.3f;
 };
 
 }  // namespace mujoco