Ignore area lights with "interface" material.

Thus, "interface" is purely for specifying medium transitions.

Issue #112.

src/pbrt/cpu/render.cpp

@@ -164,14 +164,21 @@ void CPURender(ParsedScene &parsedScene) {
                 Light area = nullptr;
                 if (sh.lightIndex != -1) {
                     CHECK_LT(sh.lightIndex, parsedScene.areaLights.size());
-                    const auto &areaLightEntity = parsedScene.areaLights[sh.lightIndex];
-
-                    area = Light::CreateArea(
-                        areaLightEntity.name, areaLightEntity.parameters,
-                        *sh.renderFromObject, mi, s, &areaLightEntity.loc, Allocator{});
-                    if (area) {
-                        std::lock_guard<std::mutex> lock(lightsMutex);
-                        lights.push_back(area);
+                    if (!mtl)
+                        Warning(&sh.loc, "Ignoring area light specification for shape "
+                                         "with \"interface\" material.");
+                    else {
+                        const auto &areaLightEntity =
+                            parsedScene.areaLights[sh.lightIndex];
+
+                        area = Light::CreateArea(areaLightEntity.name,
+                                                 areaLightEntity.parameters,
+                                                 *sh.renderFromObject, mi, s,
+                                                 &areaLightEntity.loc, Allocator{});
+                        if (area) {
+                            std::lock_guard<std::mutex> lock(lightsMutex);
+                            lights.push_back(area);
+                        }
                     }
                 }
                 if (area == nullptr && !mi.IsMediumTransition() && !alphaTex)

src/pbrt/gpu/accel.cpp

@@ -347,12 +347,16 @@ OptixTraversableHandle GPUAccel::createGASForTriangles(
         hgRecord.triRec.alphaTexture = alphaTexture;
         hgRecord.triRec.areaLights = {};
         if (shape.lightIndex != -1) {
-            // Note: this will hit if we try to have an instance as an area
-            // light.
-            auto iter = shapeIndexToAreaLights.find(shapeIndex);
-            CHECK(iter != shapeIndexToAreaLights.end());
-            CHECK_EQ(iter->second->size(), mesh->nTriangles);
-            hgRecord.triRec.areaLights = pstd::MakeSpan(*iter->second);
+            if (!material)
+                Warning(&shape.loc, "Ignoring area light specification for shape with \"interface\" material.");
+            else {
+                // Note: this will hit if we try to have an instance as an area
+                // light.
+                auto iter = shapeIndexToAreaLights.find(shapeIndex);
+                CHECK(iter != shapeIndexToAreaLights.end());
+                CHECK_EQ(iter->second->size(), mesh->nTriangles);
+                hgRecord.triRec.areaLights = pstd::MakeSpan(*iter->second);
+            }
         }
         hgRecord.triRec.mediumInterface = getMediumInterface(shape, media, alloc);
 
@@ -428,12 +432,16 @@ OptixTraversableHandle GPUAccel::createGASForBLPs(
         hgRecord.bilinearRec.alphaTexture = alphaTexture;
         hgRecord.bilinearRec.areaLights = {};
         if (shape.lightIndex != -1) {
-            auto iter = shapeIndexToAreaLights.find(shapeIndex);
-            // Note: this will hit if we try to have an instance as an area
-            // light.
-            CHECK(iter != shapeIndexToAreaLights.end());
-            CHECK_EQ(iter->second->size(), mesh->nPatches);
-            hgRecord.bilinearRec.areaLights = pstd::MakeSpan(*iter->second);
+            if (!material)
+                Warning(&shape.loc, "Ignoring area light specification for shape with \"interface\" material.");
+            else {
+                auto iter = shapeIndexToAreaLights.find(shapeIndex);
+                // Note: this will hit if we try to have an instance as an area
+                // light.
+                CHECK(iter != shapeIndexToAreaLights.end());
+                CHECK_EQ(iter->second->size(), mesh->nPatches);
+                hgRecord.bilinearRec.areaLights = pstd::MakeSpan(*iter->second);
+            }
         }
         hgRecord.bilinearRec.mediumInterface = getMediumInterface(shape, media, alloc);
 
@@ -517,12 +525,16 @@ OptixTraversableHandle GPUAccel::createGASForQuadrics(
         hgRecord.quadricRec.alphaTexture = alphaTexture;
         hgRecord.quadricRec.areaLight = nullptr;
         if (s.lightIndex != -1) {
-            auto iter = shapeIndexToAreaLights.find(shapeIndex);
-            // Note: this will hit if we try to have an instance as an area
-            // light.
-            CHECK(iter != shapeIndexToAreaLights.end());
-            CHECK_EQ(iter->second->size(), 1);
-            hgRecord.quadricRec.areaLight = (*iter->second)[0];
+            if (!material)
+                Warning(&s.loc, "Ignoring area light specification for shape with \"interface\" material.");
+            else {
+                auto iter = shapeIndexToAreaLights.find(shapeIndex);
+                // Note: this will hit if we try to have an instance as an area
+                // light.
+                CHECK(iter != shapeIndexToAreaLights.end());
+                CHECK_EQ(iter->second->size(), 1);
+                hgRecord.quadricRec.areaLight = (*iter->second)[0];
+            }
         }
         hgRecord.quadricRec.mediumInterface = getMediumInterface(s, media, alloc);
 

src/pbrt/gpu/pathintegrator.cpp

@@ -120,6 +120,25 @@ GPUPathIntegrator::GPUPathIntegrator(Allocator alloc, const ParsedScene &scene)
         const auto &shape = scene.shapes[i];
         if (shape.lightIndex == -1)
             continue;
+
+        auto isInterface = [&]() {
+            const SceneEntity *mtl = nullptr;
+            if (shape.materialIndex != -1)
+                mtl = &scene.materials[shape.materialIndex];
+            else {
+                for (auto iter = scene.namedMaterials.begin();
+                     iter != scene.namedMaterials.end(); ++iter)
+                    if (iter->first == shape.materialName) {
+                        mtl = &iter->second;
+                        break;
+                    }
+                CHECK(mtl != nullptr);
+            }
+            return (mtl->name == "interface" || mtl->name == "none" || mtl->name.empty());
+        };
+        if (isInterface())
+            continue;
+
         CHECK_LT(shape.lightIndex, scene.areaLights.size());
         const auto &areaLightEntity = scene.areaLights[shape.lightIndex];
         AnimatedTransform renderFromLight(*shape.renderFromObject);