Adds conversion settings to control the granularity of points computed for a piecewise_function

src/ifcgeom/ConversionSettings.cpp

@@ -37,3 +37,17 @@ std::istream& ifcopenshell::geometry::settings::operator>>(std::istream& in, Ite
 	}
 	return in;
 }
+
+std::istream& ifcopenshell::geometry::settings::operator>>(std::istream& in, PiecewiseStepMethod& ioo) {
+    std::string token;
+    in >> token;
+    boost::to_upper(token);
+    if (token == "MAXSTEPSIZE") {
+        ioo = MAXSTEPSIZE;
+    } else if (token == "MINSTEPS") {
+        ioo = MINSTEPS;
+    } else {
+        in.setstate(std::ios_base::failbit);
+    }
+    return in;
+}

src/ifcgeom/ConversionSettings.h

@@ -300,12 +300,29 @@ namespace ifcopenshell {
 				static constexpr const char* const description = "Overrides transparency of spaces in geometry output.";
 			};
 
+			enum PiecewiseStepMethod  {
+				MAXSTEPSIZE,
+				MINSTEPS };
+
+			std::istream& operator>>(std::istream& in, PiecewiseStepMethod& ioo);
+
+         struct PiecewiseStepType : public SettingBase<PiecewiseStepType, PiecewiseStepMethod> {
+               static constexpr const char* const name = "piecewise-step-type";
+               static constexpr const char* const description = "Indicates the method used for defining step size when evaluating piecewise curves. Provides interpretation of piecewise-step-param";
+               static constexpr PiecewiseStepMethod defaultvalue = MAXSTEPSIZE;
+         };
+
+			struct PiecewiseStepParam : public SettingBase<PiecewiseStepParam, double> {
+               static constexpr const char* const name = "piecewise-step-param";
+               static constexpr const char* const description = "Indicates the parameter value for defining step size when evaluating piecewise curves.";
+               static constexpr double defaultvalue = 0.5; // ceiling of this value is used when PiecewiseStepMethod is MinSteps
+         };
 		}
 
 		template <typename settings_t>
 		class IFC_GEOM_API SettingsContainer {
 		public:
-			typedef boost::variant<bool, int, double, std::string, std::set<int>, IteratorOutputOptions> value_variant_t;
+         typedef boost::variant<bool, int, double, std::string, std::set<int>, IteratorOutputOptions, PiecewiseStepMethod> value_variant_t;
 		private:
 			settings_t settings;
 
@@ -385,7 +402,7 @@ namespace ifcopenshell {
 		};
 
 		class IFC_GEOM_API Settings : public SettingsContainer<
-			std::tuple<MesherLinearDeflection, MesherAngularDeflection, ReorientShells, LengthUnit, PlaneUnit, Precision, IncludeCurves, IncludeSurfaces, LayersetFirst, DisableBooleanResult, NoWireIntersectionCheck, NoWireIntersectionTolerance, PrecisionFactor, DebugBooleanOperations, BooleanAttempt2d, WeldVertices, UseWorldCoords, ConvertBackUnits, ContextIds, IteratorOutput, DisableOpeningSubtractions, ApplyDefaultMaterials, DontEmitNormals, GenerateUvs, ApplyLayerSets, UseElementHierarchy, ValidateQuantities, EdgeArrows, BuildingLocalPlacement, SiteLocalPlacement, ForceSpaceTransparency>
+                                          std::tuple<MesherLinearDeflection, MesherAngularDeflection, ReorientShells, LengthUnit, PlaneUnit, Precision, IncludeCurves, IncludeSurfaces, LayersetFirst, DisableBooleanResult, NoWireIntersectionCheck, NoWireIntersectionTolerance, PrecisionFactor, DebugBooleanOperations, BooleanAttempt2d, WeldVertices, UseWorldCoords, ConvertBackUnits, ContextIds, IteratorOutput, DisableOpeningSubtractions, ApplyDefaultMaterials, DontEmitNormals, GenerateUvs, ApplyLayerSets, UseElementHierarchy, ValidateQuantities, EdgeArrows, BuildingLocalPlacement, SiteLocalPlacement, ForceSpaceTransparency, PiecewiseStepType, PiecewiseStepParam>
 		>
 		{};
 }

src/ifcgeom/mapping/IfcCompositeCurve.cpp

@@ -23,7 +23,7 @@ using namespace ifcopenshell::geometry;
 
 taxonomy::ptr mapping::map_impl(const IfcSchema::IfcCompositeCurve* inst) {
 	auto loop = taxonomy::make<taxonomy::loop>();
-	auto pwf = taxonomy::make<taxonomy::piecewise_function>();
+	auto pwf = taxonomy::make<taxonomy::piecewise_function>(&settings_);
 
 #ifdef SCHEMA_HAS_IfcSegment
 	// 4x3

src/ifcgeom/mapping/IfcCurveSegment.cpp

@@ -942,7 +942,7 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcCurveSegment* inst) {
 	auto length = fabs(cse.length());
 
 	// @todo it might be suboptimal that we no longer have the spans now
-	auto pwf = taxonomy::make<taxonomy::piecewise_function>();
+	auto pwf = taxonomy::make<taxonomy::piecewise_function>(&settings_);
 	pwf->spans.push_back({ length, fn });
 	pwf->instance = inst;
 	return pwf;

src/ifcgeom/mapping/IfcGradientCurve.cpp

@@ -28,7 +28,7 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcGradientCurve* inst) {
        Logger::Warning("Expected IfcGradientCurve.BaseCurve to be IfcCompositeCurve", inst); // CT 4.1.7.1.1.2
 
    auto horizontal = taxonomy::cast<taxonomy::piecewise_function>(map(inst->BaseCurve()));
-	auto vertical = taxonomy::make<taxonomy::piecewise_function>();
+	auto vertical = taxonomy::make<taxonomy::piecewise_function>(&settings_);
 
 	auto segments = inst->Segments();
 
@@ -73,7 +73,7 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcGradientCurve* inst) {
 		}
 	}
 
-	auto pwf = taxonomy::make<taxonomy::piecewise_function>();
+	auto pwf = taxonomy::make<taxonomy::piecewise_function>(&settings_);
 	pwf->spans.emplace_back( min_length, composition );
 	pwf->instance = inst;
 	return pwf;

src/ifcgeom/mapping/IfcOffsetCurveByDistance.cpp

@@ -46,7 +46,7 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcOffsetCurveByDistances* inst
        basis_curve_length += s.first;
    }
 
-    auto offsets = taxonomy::make<taxonomy::piecewise_function>();
+    auto offsets = taxonomy::make<taxonomy::piecewise_function>(&settings_);
 
 #if defined SCHEMA_HAS_IfcDistanceExpression
    double first_distance = first_offset_value->DistanceAlong();
@@ -153,7 +153,7 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcOffsetCurveByDistances* inst
 
    // current implementation assumes that offsets is equal to the full length of basis curve
    // this may change depending on decisions in the bSI-IF
-	auto pwf = taxonomy::make<taxonomy::piecewise_function>();
+	auto pwf = taxonomy::make<taxonomy::piecewise_function>(&settings_);
 	pwf->spans.emplace_back( basis_curve_length, composition );
 	pwf->instance = inst;
 	return pwf;

src/ifcgeom/mapping/IfcSegmentedReferenceCurve.cpp

@@ -28,7 +28,7 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcSegmentedReferenceCurve* ins
        Logger::Warning("Expected IfcSegmentedReferenceCurve.BaseCurve to be IfcGradient", inst); // CT 4.1.7.1.1.3
 		  
 	auto gradient = taxonomy::cast<taxonomy::piecewise_function>(map(inst->BaseCurve()));
-	auto cant = taxonomy::make<taxonomy::piecewise_function>();
+	auto cant = taxonomy::make<taxonomy::piecewise_function>(&settings_);
 
 	auto segments = inst->Segments();
 
@@ -76,7 +76,7 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcSegmentedReferenceCurve* ins
 		}
 	}
 
-	auto pwf = taxonomy::make<taxonomy::piecewise_function>();
+	auto pwf = taxonomy::make<taxonomy::piecewise_function>(&settings_);
 	pwf->spans.emplace_back( min_length, composition );
 	pwf->instance = inst;
 	return pwf;

src/ifcgeom/taxonomy.cpp

@@ -460,10 +460,19 @@ ifcopenshell::geometry::taxonomy::item::ptr ifcopenshell::geometry::taxonomy::pi
 
    std::vector<taxonomy::point3::ptr> polygon;
 	
-	static const double target_resolution = 0.5;
+	auto param_type = settings_ ? settings_->get<ifcopenshell::geometry::settings::PiecewiseStepType>().get() : ifcopenshell::geometry::settings::PiecewiseStepMethod::MAXSTEPSIZE;
-	int num_steps = (int)std::ceil(length / target_resolution);
+   auto param = settings_ ? settings_->get<ifcopenshell::geometry::settings::PiecewiseStepParam>().get() : 0.5;
-   auto resolution = length / num_steps;
+   int num_steps = 0;
-	for (int i = 0; i <= num_steps; ++i) {
+   if (param_type == ifcopenshell::geometry::settings::PiecewiseStepMethod::MAXSTEPSIZE) {
+	   // parameter is max step size
+      num_steps = (int)std::ceil(length / param);
+   } else {
+	   // parameter is minimum number of steps
+      num_steps = (int)std::ceil(param);
+    }
+    auto resolution = length / num_steps;
+
+	 for (int i = 0; i <= num_steps; ++i) {
 		auto u = resolution * i;
       Eigen::Matrix4d m = evaluate(u);
       polygon.push_back(taxonomy::make<taxonomy::point3>(m.col(3)(0), m.col(3)(1), m.col(3)(2)));

src/ifcgeom/taxonomy.h

@@ -3,6 +3,8 @@
 
 #include "../ifcparse/IfcBaseClass.h"
 
+#include "ConversionSettings.h"
+
 #include <boost/variant.hpp>
 #include <boost/functional/hash.hpp>
 
@@ -127,6 +129,7 @@ typedef item const* ptr;
 
 			struct implicit_item : public item {
 				DECLARE_PTR(implicit_item)
+				using item::item;
 
 				virtual item::ptr evaluate() const = 0;
 			};
@@ -134,6 +137,13 @@ typedef item const* ptr;
 			struct piecewise_function : public implicit_item {
 				DECLARE_PTR(piecewise_function)
 
+				piecewise_function(const IfcUtil::IfcBaseInterface* instance = nullptr) : implicit_item(instance){};
+				piecewise_function(ifcopenshell::geometry::Settings* settings) : settings_(settings){};
+            piecewise_function(piecewise_function&&) = default;
+            piecewise_function(const piecewise_function&) = default;
+
+				ifcopenshell::geometry::Settings* settings_ = nullptr;
+
 				// length of span, function to evaluate span
 				std::vector<std::pair<double, std::function<Eigen::Matrix4d(double u)>>> spans;