Fix constant to be opaque

src/emitters/constant.cpp

@@ -55,7 +55,7 @@ class ConstantBackgroundEmitter final : public Emitter<Float, Spectrum> {
     ConstantBackgroundEmitter(const Properties &props) : Base(props) {
         /* Until `set_scene` is called, we have no information
            about the scene and default to the unit bounding sphere. */
-        m_bsphere = ScalarBoundingSphere3f(ScalarPoint3f(0.f), 1.f);
+        m_bsphere = BoundingSphere3f(ScalarPoint3f(0.f), 1.f);
         m_surface_area = 4.f * dr::Pi<ScalarFloat>;
 
         m_radiance = props.texture_d65<Texture>("radiance", 1.f);
@@ -74,16 +74,22 @@ class ConstantBackgroundEmitter final : public Emitter<Float, Spectrum> {
 
     void set_scene(const Scene *scene) override {
         if (scene->bbox().valid()) {
-            m_bsphere = scene->bbox().bounding_sphere();
+            ScalarBoundingSphere3f scene_sphere =
+                scene->bbox().bounding_sphere();
+            m_bsphere = BoundingSphere3f(scene_sphere.center, scene_sphere.radius);
             m_bsphere.radius =
                 dr::maximum(math::RayEpsilon<Float>,
                         m_bsphere.radius * (1.f + math::RayEpsilon<Float>));
         } else {
-            m_bsphere = ScalarBoundingSphere3f(ScalarPoint3f(0.f), 1.f);
+            m_bsphere.center = 0.f;
+            m_bsphere.radius = math::RayEpsilon<Float>;
         }
         m_surface_area = 4.f * dr::Pi<ScalarFloat> * dr::sqr(m_bsphere.radius);
+
+        dr::make_opaque(m_bsphere.center, m_bsphere.radius, m_surface_area);
     }
 
+
     Spectrum eval(const SurfaceInteraction3f &si, Mask active) const override {
         MI_MASKED_FUNCTION(ProfilerPhase::EndpointEvaluate, active);
 
@@ -195,10 +201,10 @@ class ConstantBackgroundEmitter final : public Emitter<Float, Spectrum> {
     MI_DECLARE_CLASS()
 protected:
     ref<Texture> m_radiance;
-    ScalarBoundingSphere3f m_bsphere;
+    BoundingSphere3f m_bsphere;
 
     /// Surface area of the bounding sphere
-    ScalarFloat m_surface_area;
+    Float m_surface_area;
 };
 
 MI_IMPLEMENT_CLASS_VARIANT(ConstantBackgroundEmitter, Emitter)