Add Filament lighting and shadow features and fixes.

- Add a hidden directional light to Filament scenes with no lights to work around soft shadow blackout bug.
- Respect quality/shadowsize as default shadow map resolution.
- Interpret light/bulbradius in correct units for each shadow type and update XML reference docs.
- Support updating the shadow map resolution of live Filament lights.
- Clamp light intensities to non-negative values in the Filament debug panel.

PiperOrigin-RevId: 957305808
Change-Id: Ic7a3430aaa3b117be7fbb7ace836d68e54cdf65a

doc/APIreference/functions.rst

@@ -3429,6 +3429,15 @@ Enables or disables the light.
 
 Sets the intensity of the light, in candela.
 
+.. _mjrf_setLightShadowMapSize:
+
+`mjrf_setLightShadowMapSize <#mjrf_setLightShadowMapSize>`__
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. mujoco-include:: mjrf_setLightShadowMapSize
+
+Sets the resolution of the light's shadow map, in texels.
+
 .. _mjrf_setLightColor:
 
 `mjrf_setLightColor <#mjrf_setLightColor>`__

doc/XMLreference.rst

@@ -3301,8 +3301,8 @@ Attributes may be applied or ignored depending on the lighting model being used.
 .. _body-light-bulbradius:
 
 :at:`bulbradius`: :at-val:`real, "0.02"`
-   The radius of the light source which can affect shadow softness depending on the
+   The radius of the light-emitting surface. Larger radii produce softer shadows in renderers that
-   renderer. This only applies to spotlights.
+   support soft shadows. Ignored by the classic renderer.
 
 .. _body-light-attenuation:
 

doc/includes/references.h

@@ -3442,6 +3442,7 @@ mjrfLight* mjrf_createLight(mjrfContext* ctx, const mjrfLightParams* params);
 void mjrf_destroyLight(mjrfLight* light);
 void mjrf_setLightEnabled(mjrfLight* light, mjtBool enabled);
 void mjrf_setLightIntensity(mjrfLight* light, float intensity);
+void mjrf_setLightShadowMapSize(mjrfLight* light, int map_size);
 void mjrf_setLightColor(mjrfLight* light, const float color[3]);
 void mjrf_setLightTransform(mjrfLight* light, const float position[3], const float direction[3]);
 int mjrf_getLightType(const mjrfLight* light);

include/mujoco/mjrfilament.h

@@ -281,6 +281,9 @@ void mjrf_setLightEnabled(mjrfLight* light, mjtBool enabled);
 // Sets the intensity of the light, in candela.
 void mjrf_setLightIntensity(mjrfLight* light, float intensity);
 
+// Sets the resolution of the light's shadow map, in texels.
+void mjrf_setLightShadowMapSize(mjrfLight* light, int map_size);
+
 // Sets the RGB color of the light.
 void mjrf_setLightColor(mjrfLight* light, const float color[3]);
 

src/experimental/filament/compat/scene_bridge.cc

@@ -100,6 +100,8 @@ mat4 CalculateClipFromWorld(const mjrRect& viewport, const mjrCamera& cam) {
 void SceneBridge::Update(const mjrRect& viewport, const mjvScene* scene) {
   const mjModel* model = model_objects_->GetModel();
 
+  model_lights_->Update();
+
   mjtNum hpos[3], hfwd[3];
   float headpos[3], gazedir[3];
   mjv_cameraInModel(hpos, hfwd, nullptr, scene);

src/render/filament/core/imgui_editor.cc

@@ -187,6 +187,19 @@ bool Ui(std::string_view label, T* value, UiOpts<T> opts = {}) {
     static_assert(dependent_false<T>::value, "Unsupported type");
   }
 
+  // The Drag widgets above do not enforce bounds when only one of min/max is
+  // given, and typed input (ctrl+click) bypasses Slider bounds; clamp here.
+  if constexpr (std::is_arithmetic_v<T> && !std::is_same_v<T, bool>) {
+    if (changed) {
+      if (opts.min.has_value()) {
+        *value = std::max(*value, *opts.min);
+      }
+      if (opts.max.has_value()) {
+        *value = std::min(*value, *opts.max);
+      }
+    }
+  }
+
   if (modified) {
     ImGui::PopStyleColor();
     ImGui::SetItemTooltip("RMB to revert change");
@@ -565,7 +578,7 @@ void DrawIndirectLightGui(SceneView* scene_view) {
   float intensity = 10000.0f;
   if (ibl) {
     intensity = ibl->getIntensity();
-    if (Ui("Intensity", &intensity, {.step = 1000.0f, .fstep = 10000.0f})) {
+    if (Ui("Intensity", &intensity, {.min = 0.0f, .step = 1000.0f, .fstep = 10000.0f})) {
       ibl->setIntensity(intensity);
     }
   }
@@ -586,7 +599,7 @@ void DrawLightGui(filament::LightManager& lm,
     lm.setDirection(li, direction);
   }
   float intensity = lm.getIntensity(li);
-  if (Ui("Intensity", &intensity, {.step = 1000.0f, .fstep = 10000.0f})) {
+  if (Ui("Intensity", &intensity, {.min = 0.0f, .step = 1000.0f, .fstep = 10000.0f})) {
     lm.setIntensityCandela(li, intensity);
   }
   float falloff = lm.getFalloff(li);

src/render/filament/core/light.cc

@@ -165,6 +165,18 @@ void Light::SetIntensity(float intensity) {
   }
 }
 
+void Light::SetShadowMapSize(int map_size) {
+  params_.shadow_map_size = map_size;
+  if (ibl_) {
+    return;
+  }
+  filament::LightManager& lm = engine_->getLightManager();
+  const filament::LightManager::Instance li = lm.getInstance(entity_);
+  filament::LightManager::ShadowOptions opts = lm.getShadowOptions(li);
+  opts.mapSize = map_size;
+  lm.setShadowOptions(li, opts);
+}
+
 void Light::Enable() {
   if (!enabled_) {
     enabled_ = true;

src/render/filament/core/light.h

@@ -51,6 +51,9 @@ class Light : public mjrfLight {
   // Sets the intensity of this light, in candela.
   void SetIntensity(float intensity);
 
+  // Sets the resolution of this light's shadow map, in texels.
+  void SetShadowMapSize(int map_size);
+
   // Returns the type of the light.
   mjtLightType GetType() const;
 

src/render/filament/mjrfilament.cc

@@ -234,6 +234,10 @@ void mjrf_setLightIntensity(mjrfLight* light, float intensity) {
   mujoco::Light::downcast(light)->SetIntensity(intensity);
 }
 
+void mjrf_setLightShadowMapSize(mjrfLight* light, int map_size) {
+  mujoco::Light::downcast(light)->SetShadowMapSize(map_size);
+}
+
 void mjrf_setLightColor(mjrfLight* light, const float color[3]) {
   mujoco::Light::downcast(light)->SetColor({color[0], color[1], color[2]});
 }

src/render/filament/support/model_lights.cc

@@ -14,10 +14,13 @@
 
 #include "render/filament/support/model_lights.h"
 
+#include <algorithm>
 #include <memory>
+#include <numbers>
 #include <string>
 #include <utility>
 
+#include <math/TVecHelpers.h>
 #include <math/mat4.h>
 #include <math/mathfwd.h>
 #include <math/vec3.h>
@@ -74,8 +77,7 @@ static UniquePtr<mjrfTexture> CreateFallbackIndirectLightTexture(
 ModelLights::ModelLights(mjrfScene* scene, ModelObjects* model_objects)
     : scene_(scene), model_objects_(model_objects) {
   const mjModel* model = model_objects->GetModel();
-  default_shadow_map_size_ =
+  shadowsize_ = model->vis.quality.shadowsize;
-      ReadElement(model, "filament.shadows.map_size", default_shadow_map_size_);
   fallback_head_light_intensity_ =
       ReadElement(model, "filament.fallback.head_light_intensity",
                   fallback_head_light_intensity_);
@@ -97,16 +99,28 @@ ModelLights::~ModelLights() {
     mjrf_removeLightFromScene(scene_, fallback_ibl_.get());
   }
   fallback_ibl_.reset();
+  if (fallback_directional_) {
+    mjrf_removeLightFromScene(scene_, fallback_directional_.get());
+  }
+  fallback_directional_.reset();
 }
 
 void ModelLights::Prepare() {
   mjrfContext* ctx = model_objects_->GetContext();
   const mjModel* model = model_objects_->GetModel();
 
+  // Default to the shadow map resolution in mjVisual, like the classic
+  // renderer. Filament clamps shadow map sizes to 2048.
+  int default_shadow_map_size = std::min(model->vis.quality.shadowsize, 2048);
+  default_shadow_map_size =
+      ReadElement(model, "filament.shadows.map_size", default_shadow_map_size);
+
   bool has_image_based_light = false;
+  bool has_directional_light = false;
   float total_light_intensity = 0.0f;
   for (int i = 0; i < model->nlight; ++i) {
     total_light_intensity += model->light_intensity[i];
+    has_directional_light |= model->light_type[i] == mjLIGHT_DIRECTIONAL;
 
     if (model->light_type[i] == mjLIGHT_IMAGE) {
       mjrfLightParams params;
@@ -126,13 +140,42 @@ void ModelLights::Prepare() {
       params.color[2] = model->light_diffuse[2];
       params.type = (mjtLightType)model->light_type[i];
       params.cast_shadows = model->light_castshadow[i];
-      // The bulb_radius is only used by DPCF or PCSS shadows. For VSM shadows,
+      // light_bulbradius is the radius of the emitting surface in meters.
-      // we use light_bulbradius to control the blur width.
+      // Filament's DPCF/PCSS internally scale shadowBulbRadius from meters
-      params.bulb_radius = model->light_bulbradius[i];
+      // to light-space texels, so we pass it through in meters for all types.
-      params.vsm_blur_width = model->light_bulbradius[i];
+      // VSM requires a single uniform blur width for the map; we approximate
+      // this using the angular size of the bulb from the scene center.
+      const float bulb_radius = model->light_bulbradius[i];
+      const float map_size = default_shadow_map_size;
+      const float3 to_center = ReadFloat3(model->stat.center) -
+                               ReadFloat3(model->light_pos0, i);
+      const float distance = std::max(length(to_center), 1e-6f);
+      const float bulb_angle = bulb_radius / distance;
+      params.bulb_radius = bulb_radius;
+      switch (params.type) {
+        case mjLIGHT_SPOT: {
+          const float fov =
+              2.0f * model->light_cutoff[i] * std::numbers::pi / 180.0f;
+          params.vsm_blur_width = bulb_angle * map_size / fov;
+          break;
+        }
+        case mjLIGHT_POINT:
+          params.vsm_blur_width =
+              bulb_angle * map_size / (0.5f * std::numbers::pi);
+          break;
+        case mjLIGHT_DIRECTIONAL: {
+          const float coverage =
+              2.0f * model->vis.map.shadowclip * model->stat.extent;
+          params.vsm_blur_width = bulb_radius * map_size / coverage;
+          break;
+        }
+        default:
+          break;
+      }
+      params.vsm_blur_width = std::min(params.vsm_blur_width, 125.0f);
       params.range = model->light_range[i];
       params.intensity = model->light_intensity[i];
-      params.shadow_map_size = default_shadow_map_size_;
+      params.shadow_map_size = default_shadow_map_size;
       if (params.type == mjLIGHT_SPOT) {
         params.spot_cone_angle = model->light_cutoff[i];
       }
@@ -162,6 +205,23 @@ void ModelLights::Prepare() {
     lights_.emplace_back(std::move(light_obj));
   }
 
+  // Workaround for an upstream filament bug, present since 1.74.0
+  // (https://github.com/google/filament/issues/10249): under the non-PCF
+  // shadow types (VSM/DPCF/PCSS), a scene where a punctual (spot/point) light
+  // casts shadows renders fully black unless a directional light is also
+  // present. Mere presence suffices: zero intensity, shadows off. Keep
+  // filament's directional slot occupied with an invisible light whenever the
+  // model has no directional light.
+  if (!has_directional_light) {
+    mjrfLightParams params;
+    mjrf_defaultLightParams(&params);
+    params.type = mjLIGHT_DIRECTIONAL;
+    params.cast_shadows = 0;
+    params.intensity = 0.0f;
+    fallback_directional_ = CreateLight(ctx, params);
+    mjrf_addLightToScene(scene_, fallback_directional_.get());
+  }
+
   if (!has_image_based_light && total_light_intensity > 0.0f) {
     // Create a black indirect light to ensure that the skybox is
     // oriented to respect mujoco's Z-up convention.
@@ -203,7 +263,22 @@ void ModelLights::Prepare() {
   mjrf_setSceneSkybox(scene_, model_objects_->GetSkyboxTexture());
 }
 
+void ModelLights::UpdateShadowMapSize() {
+  const mjModel* model = model_objects_->GetModel();
+  if (model->vis.quality.shadowsize != shadowsize_) {
+    shadowsize_ = model->vis.quality.shadowsize;
+    const int map_size = std::min(shadowsize_, 2048);
+    for (auto& light : lights_) {
+      mjrf_setLightShadowMapSize(light.get(), map_size);
+    }
+  }
+}
+
 void ModelLights::Update(const mjData* data) {
+  UpdateShadowMapSize();
+  if (data == nullptr) {
+    return;
+  }
   const mjModel* model = model_objects_->GetModel();
   for (int i = 0; i <= model->nlight; ++i) {
     // Light with index nlight is the headlight.

src/render/filament/support/model_lights.h

@@ -31,7 +31,7 @@ class ModelLights {
   ~ModelLights();
 
   // Updates the state of the lights in the scene.
-  void Update(const mjData* data);
+  void Update(const mjData* data = nullptr);
 
   // Returns the light with the given index in the mjModel. Note that an extra
   // headlight is assigned of the index `nlight`.
@@ -43,13 +43,19 @@ class ModelLights {
  private:
   void Prepare();
 
+  // Applies changes of mjVisual quality.shadowsize to the lights' shadow
+  // maps. A filament.shadows.map_size custom element remains in effect until
+  // shadowsize is edited.
+  void UpdateShadowMapSize();
+
   mjrfScene* scene_ = nullptr;
   ModelObjects* model_objects_ = nullptr;
 
   UniquePtr<mjrfLight> fallback_ibl_{nullptr, nullptr};
+  UniquePtr<mjrfLight> fallback_directional_{nullptr, nullptr};
   UniquePtr<mjrfTexture> fallback_ibl_texture_{nullptr, nullptr};
   std::vector<UniquePtr<mjrfLight>> lights_;
-  int default_shadow_map_size_ = 2048;
+  int shadowsize_ = 0;
   float fallback_head_light_intensity_ = 0.f;
   float fallback_scene_light_intensity_ = 80'000.f;
   float fallback_environment_light_intensity_ = 5'000.f;