ObjectInstance has influence on scene bound (used by e.g. InfiniteAreaLight)

[wahn]

The scene gitlab/rs-pbrt-test-scenes/pbrt/pbrt_vw_van/vw-van.pbrt (on GitLab rs-pbrt-test-scenes) contains 240 ObjectInstance lines:

$ pwd
/home/jan/git/gitlab/rs-pbrt-test-scenes/pbrt/pbrt_vw_van
$ grep ObjectInstance vw-van.pbrt | wc -l
240

So far the Rust code seems to ignore them (because I didn't see any geometry missing), but it seems to mess up the scene bound, which is used in InfiniteAreaLight:

$ tail gdb.txt -n 6
world_center
x = -500, y = 177.225449, z = 850 C++
x = -500, y = 177.264572, z = 850 Rust
world_radius
2730.18994 C++
2730.18726 Rust

[wahn]

(gdb) set args --nthreads 1 vw-van.pbrt
(gdb) b api.cpp:1572

1550 void pbrtObjectInstance(const std::string &name) {
1551     VERIFY_WORLD("ObjectInstance");
1552     if (PbrtOptions.cat || PbrtOptions.toPly) {
1553         printf("%*sObjectInstance \"%s\"\n", catIndentCount, "", name.c_str());
1554         return;
1555     }
1556 
1557     // Perform object instance error checking
1558     if (renderOptions->currentInstance) {
1559         Error("ObjectInstance can't be called inside instance definition");
1560         return;
1561     }
1562     if (renderOptions->instances.find(name) == renderOptions->instances.end()) {
1563         Error("Unable to find instance named \"%s\"", name.c_str());
1564         return;
1565     }
1566     std::vector<std::shared_ptr<Primitive>> &in =
1567         renderOptions->instances[name];
1568     if (in.empty()) return;
1569     ++nObjectInstancesUsed;
1570     if (in.size() > 1) {
1571         // Create aggregate for instance _Primitive_s
1572         std::shared_ptr<Primitive> accel(
1573             MakeAccelerator(renderOptions->AcceleratorName, std::move(in),
1574                             renderOptions->AcceleratorParams));
1575         if (!accel) accel = std::make_shared<BVHAccel>(in);
1576         in.clear();
1577         in.push_back(accel);
1578     }
1579     static_assert(MaxTransforms == 2,
1580                   "TransformCache assumes only two transforms");
1581     // Create _animatedInstanceToWorld_ transform for instance
1582     Transform *InstanceToWorld[2] = {
1583         transformCache.Lookup(curTransform[0]),
1584         transformCache.Lookup(curTransform[1])
1585     };
1586     AnimatedTransform animatedInstanceToWorld(
1587         InstanceToWorld[0], renderOptions->transformStartTime,
1588         InstanceToWorld[1], renderOptions->transformEndTime);
1589     std::shared_ptr<Primitive> prim(
1590         std::make_shared<TransformedPrimitive>(in[0], animatedInstanceToWorld));
1591     renderOptions->primitives.push_back(prim);
1592 }

So, we found 60 Primitive values in the vector renderOptions->instances at that point:

(gdb) print name
$8 = "Null.60"
(gdb) print in
$6 = std::vector of length 60, capacity 96 = {std::shared_ptr<pbrt::Primitive> ...

[wahn]

(gdb) b 1529
Breakpoint 2 at 0x55555583d9bc: file /home/jan/git/github/pbrt-v3/src/core/api.cpp, line 1529.

1524 void pbrtObjectBegin(const std::string &name) {
1525     VERIFY_WORLD("ObjectBegin");
1526     pbrtAttributeBegin();
1527     if (renderOptions->currentInstance)
1528         Error("ObjectBegin called inside of instance definition");
1529     renderOptions->instances[name] = std::vector<std::shared_ptr<Primitive>>();
1530     renderOptions->currentInstance = &renderOptions->instances[name];
1531     if (PbrtOptions.cat || PbrtOptions.toPly)
1532         printf("%*sObjectBegin \"%s\"\n", catIndentCount, "", name.c_str());
1533 }

So, after executing line 1530, we got an empty vector pointed to by renderOptions->currentInstance:

(gdb) print *renderOptions->currentInstance
$14 = std::vector of length 0, capacity 0

On the Rust side we have that too:

(gdb) print *instance
$5 = Vec<alloc::sync::Arc<Primitive>>(len: 0, cap: 0)

[wahn]

(gdb) b 1412
Breakpoint 3 at 0x55555583ca17: file /home/jan/git/github/pbrt-v3/src/core/api.cpp, line 1412.
(gdb) run
(gdb) where
#0  pbrt::pbrtShape (name="plymesh", params=...) at /home/jan/git/github/pbrt-v3/src/core/api.cpp:1412

1410     // Add _prims_ and _areaLights_ to scene or current instance
1411     if (renderOptions->currentInstance) {
1412         if (areaLights.size())
1413             Warning("Area lights not supported with object instancing");
1414         renderOptions->currentInstance->insert(
1415             renderOptions->currentInstance->end(), prims.begin(), prims.end());
1416     } else {
1417         renderOptions->primitives.insert(renderOptions->primitives.end(),
1418                                          prims.begin(), prims.end());
1419         if (areaLights.size())
1420             renderOptions->lights.insert(renderOptions->lights.end(),
1421                                          areaLights.begin(), areaLights.end());
1422     }

The first time line 1414 gets executed we inserted 12 Primitive values (in C++):

(gdb) print *renderOptions->currentInstance
$20 = std::vector of length 12, capacity 12 = {std::shared_ptr<pbrt::Primitive>

On the Rust side we have that too:

1: *current_instance = Vec<alloc::sync::Arc<Primitive>>(len: 12, cap: 16) = {Arc<Primitive> = ...

[wahn]

Commit 52bdd2e resolves this issue:

Before:

world_center
x = -500, y = 177.225449, z = 850 C++
x = -500, y = 177.264572, z = 850 Rust
world_radius
2730.18994 C++
2730.18726 Rust

After:

world_center
x = -500, y = 177.225449, z = 850 C++
x = -500, y = 177.225449, z = 850 Rust
world_radius
2730.18994 C++
2730.18994 Rust