Fix rounding errors breaking buffer sizes of large gltf models (#810)

- Add uint64_t/int64_t types to the JsonObj class so that sizes never
touch floats
- In match graph diagrams, color nodes with obs-crossing boundary edges
in red instead of in black

Author: Strilanc

src/stim/diagram/basic_3d_diagram.cc

@@ -60,7 +60,7 @@ GltfScene Basic3dDiagram::to_gltf_scene() const {
     });
 
     auto buf_purple_scattered_lines = std::shared_ptr<GltfBuffer<3>>(new GltfBuffer<3>{
-        {"buf_blue_scattered_lines"},
+        {"buf_purple_scattered_lines"},
         purple_line_data,
     });
 

src/stim/diagram/gate_data_3d.cc

@@ -342,7 +342,7 @@ std::pair<std::string_view, std::shared_ptr<GltfMesh>> make_z_control_mesh() {
     return {"Z_CONTROL", mesh};
 }
 
-std::pair<std::string_view, std::shared_ptr<GltfMesh>> make_detector_mesh() {
+std::pair<std::string_view, std::shared_ptr<GltfMesh>> make_detector_mesh(bool excited) {
     auto circle = make_circle_loop(8, CONTROL_RADIUS, true);
     auto circle2 = make_circle_loop(8, CONTROL_RADIUS, true);
     auto circle3 = make_circle_loop(8, CONTROL_RADIUS, true);
@@ -354,44 +354,44 @@ std::pair<std::string_view, std::shared_ptr<GltfMesh>> make_detector_mesh() {
         std::swap(e.xyz[0], e.xyz[1]);
         std::swap(e.xyz[1], e.xyz[2]);
     }
-    auto black_material = std::shared_ptr<GltfMaterial>(new GltfMaterial{
-        {"black"},
-        {0, 0, 0, 1},
+    auto material = std::shared_ptr<GltfMaterial>(new GltfMaterial{
+        {excited ? "det_red" : "det_black"},
+        {excited ? 1.0f : 0.0f, excited ? 0.5f : 0.0f, excited ? 0.5f : 0.0f, 1},
         1,
         1,
         true,
         nullptr,
     });
     auto disc_interior = std::shared_ptr<GltfPrimitive>(new GltfPrimitive{
-        {"detector_primitive_circle_interior"},
+        {excited ? "excited_detector_primitive_circle_interior" : "detector_primitive_circle_interior"},
         GL_TRIANGLE_FAN,
         circle,
         nullptr,
-        black_material,
+        material,
     });
     auto disc_interior2 = std::shared_ptr<GltfPrimitive>(new GltfPrimitive{
-        {"detector_primitive_circle_interior_2"},
+        {excited ? "excited_detector_primitive_circle_interior_2" : "detector_primitive_circle_interior_2"},
         GL_TRIANGLE_FAN,
         circle2,
         nullptr,
-        black_material,
+        material,
     });
     auto disc_interior3 = std::shared_ptr<GltfPrimitive>(new GltfPrimitive{
-        {"detector_primitive_circle_interior_3"},
+        {excited ? "excited_detector_primitive_circle_interior_3" : "detector_primitive_circle_interior_3"},
         GL_TRIANGLE_FAN,
         circle3,
         nullptr,
-        black_material,
+        material,
     });
     auto mesh = std::shared_ptr<GltfMesh>(new GltfMesh{
-        {"mesh_DETECTOR"},
+        {excited ? "mesh_EXCITED_DETECTOR" : "mesh_DETECTOR"},
         {
             disc_interior,
             disc_interior2,
             disc_interior3,
         },
     });
-    return {"DETECTOR", mesh};
+    return {excited ? "EXCITED_DETECTOR" : "DETECTOR", mesh};
 }
 
 std::map<std::string_view, std::shared_ptr<GltfMesh>> stim_draw_internal::make_gate_primitives() {
@@ -516,6 +516,7 @@ std::map<std::string_view, std::shared_ptr<GltfMesh>> stim_draw_internal::make_g
         make_z_control_mesh(),
         make_xswap_control_mesh(),
         make_zswap_control_mesh(),
-        make_detector_mesh(),
+        make_detector_mesh(false),
+        make_detector_mesh(true),
     };
 }

src/stim/diagram/gltf.cc

@@ -31,14 +31,14 @@ JsonObj GltfScene::_to_json_local() const {
 JsonObj GltfScene::to_json() {
     // Clear indices.
     visit([&](GltfId &item_id, const char *type, const std::function<JsonObj(void)> &to_json, uintptr_t abs_id) {
-        item_id.index = SIZE_MAX;
+        item_id.index = UINT64_MAX;
     });
 
     // Re-index.
     std::map<std::string, size_t> counts;
     visit([&](GltfId &item_id, const char *type, const std::function<JsonObj(void)> &to_json, uintptr_t abs_id) {
         auto &c = counts[type];
-        if (item_id.index == SIZE_MAX || item_id.index == c) {
+        if (item_id.index == UINT64_MAX || item_id.index == c) {
             item_id.index = c;
             c++;
         } else if (item_id.index > c) {
@@ -97,7 +97,8 @@ void GltfImage::visit(const gltf_visit_callback &callback) {
 
 JsonObj GltfImage::to_json() const {
     return std::map<std::string, JsonObj>{
-        {"name", id.name},
+        // Note: saving space by not including names.
+        //{"name", id.name},
         {"uri", uri},
     };
 }
@@ -116,7 +117,8 @@ void GltfTexture::visit(const gltf_visit_callback &callback) {
 
 JsonObj GltfTexture::to_json() const {
     return std::map<std::string, JsonObj>{
-        {"name", id.name},
+        // Note: saving space by not including names.
+//        {"name", id.name},
         {"sampler", 0},
         {"source", 0},
     };
@@ -137,7 +139,7 @@ void GltfMaterial::visit(const gltf_visit_callback &callback) {
 
 JsonObj GltfMaterial::to_json() const {
     JsonObj result = std::map<std::string, JsonObj>{
-        {"name", id.name},
+//        {"name", id.name},
         {"pbrMetallicRoughness",
          std::map<std::string, JsonObj>{
              {"baseColorFactor",

src/stim/diagram/gltf.h

@@ -11,30 +11,23 @@
 
 namespace stim_draw_internal {
 
-constexpr size_t GL_FLOAT = 5126;
-constexpr size_t GL_ARRAY_BUFFER = 34962;
-constexpr size_t GL_UNSIGNED_SHORT = 5123;
-constexpr size_t GL_ELEMENT_ARRAY_BUFFER = 34963;
-constexpr size_t GL_TRIANGLE_STRIP = 5;
-constexpr size_t GL_TRIANGLES = 4;
-constexpr size_t GL_TRIANGLE_FAN = 6;
-
-constexpr size_t GL_LINES = 1;
-constexpr size_t GL_LINE_STRIP = 3;
-constexpr size_t GL_LINE_LOOP = 2;
-
-constexpr size_t GL_REPEAT = 10497;
-constexpr size_t GL_CLAMP = 10496;
-constexpr size_t GL_CLAMP_TO_EDGE = 33071;
-constexpr size_t GL_LINEAR = 9729;
-constexpr size_t GL_LINEAR_MIPMAP_NEAREST = 9987;
-constexpr size_t GL_NEAREST = 9728;
+constexpr uint64_t GL_FLOAT = 5126;
+constexpr uint64_t GL_ARRAY_BUFFER = 34962;
+constexpr uint64_t GL_TRIANGLES = 4;
+constexpr uint64_t GL_TRIANGLE_FAN = 6;
+
+constexpr uint64_t GL_LINES = 1;
+constexpr uint64_t GL_LINE_STRIP = 3;
+constexpr uint64_t GL_LINE_LOOP = 2;
+
+constexpr uint64_t GL_CLAMP_TO_EDGE = 33071;
+constexpr uint64_t GL_NEAREST = 9728;
 
 struct GltfId {
     std::string name;
-    size_t index;
+    uint64_t index;
 
-    GltfId(std::string name) : name(name), index(SIZE_MAX) {
+    GltfId(std::string name) : name(name), index(UINT64_MAX) {
     }
     GltfId() = delete;
 };
@@ -81,7 +74,7 @@ struct GltfBuffer {
         return std::map<std::string, JsonObj>{
             {"name", id.name},
             {"uri", ss.str()},
-            {"byteLength", vertex_data_size},
+            {"byteLength", (uint64_t)vertex_data_size},
         };
     }
 
@@ -90,7 +83,7 @@ struct GltfBuffer {
             {"name", id.name},
             {"buffer", id.index},
             {"byteOffset", 0},
-            {"byteLength", vertices.size() * sizeof(Coord<DIM>)},
+            {"byteLength", (uint64_t)(vertices.size() * sizeof(Coord<DIM>))},
             {"target", GL_ARRAY_BUFFER},
         };
     }
@@ -115,7 +108,7 @@ struct GltfBuffer {
             {"bufferView", id.index},
             {"byteOffset", 0},
             {"componentType", GL_FLOAT},
-            {"count", vertices.size()},
+            {"count", (uint64_t)vertices.size()},
             {"type", "VEC" + std::to_string(DIM)},
             {"min", std::move(min_v)},
             {"max", std::move(max_v)},
@@ -125,10 +118,10 @@ struct GltfBuffer {
 
 struct GltfSampler {
     GltfId id;
-    size_t magFilter;
-    size_t minFilter;
-    size_t wrapS;
-    size_t wrapT;
+    uint64_t magFilter;
+    uint64_t minFilter;
+    uint64_t wrapS;
+    uint64_t wrapT;
 
     void visit(const gltf_visit_callback &callback);
     JsonObj to_json() const;
@@ -165,7 +158,7 @@ struct GltfMaterial {
 
 struct GltfPrimitive {
     GltfId id;
-    size_t element_type;
+    uint64_t element_type;
     std::shared_ptr<GltfBuffer<3>> position_buffer;
     std::shared_ptr<GltfBuffer<2>> tex_coords_buffer;
     std::shared_ptr<GltfMaterial> material;

src/stim/diagram/graph/match_graph_3d_drawer.cc

@@ -79,6 +79,7 @@ Basic3dDiagram stim_draw_internal::dem_match_graph_to_basic_3d_diagram(const sti
     auto minmax = Coord<3>::min_max(coords);
     auto center = (minmax.first + minmax.second) * 0.5;
 
+    std::set<uint64_t> boundary_observable_detectors;
     std::vector<Coord<3>> det_coords;
     auto handle_contiguous_targets = [&](SpanRef<const DemTarget> targets) {
         bool has_observables = false;
@@ -102,6 +103,13 @@ Basic3dDiagram stim_draw_internal::dem_match_graph_to_basic_3d_diagram(const sti
             }
             auto a = det_coords[0];
             det_coords.push_back(a + d * 10);
+            if (has_observables) {
+                for (auto t : targets) {
+                    if (t.is_relative_detector_id()) {
+                        boundary_observable_detectors.insert(t.val());
+                    }
+                }
+            }
         }
         if (det_coords.size() == 2) {
             if (has_observables) {
@@ -129,10 +137,6 @@ Basic3dDiagram stim_draw_internal::dem_match_graph_to_basic_3d_diagram(const sti
         }
     };
 
-    for (const auto &c : coords) {
-        out.elements.push_back({"DETECTOR", c});
-    }
-
     dem.iter_flatten_error_instructions([&](const DemInstruction &op) {
         if (op.type != DemInstructionType::DEM_ERROR) {
             return;
@@ -148,5 +152,10 @@ Basic3dDiagram stim_draw_internal::dem_match_graph_to_basic_3d_diagram(const sti
         handle_contiguous_targets({p + start, op.target_data.ptr_end});
     });
 
+    for (size_t k = 0; k < coords.size(); k++) {
+        bool excited = boundary_observable_detectors.find(k) != boundary_observable_detectors.end();
+        out.elements.push_back({excited ? "EXCITED_DETECTOR" : "DETECTOR", coords[k]});
+    }
+
     return out;
 }