Fix unit handling in an edge case.

Author: kovacsv

dist/occt-import-js.wasm

@@ -127,6 +127,7 @@ int main (int argc, const char* argv[])
     }
 
     ImportParams params;
+    params.linearUnit = ImportParams::LinearUnit::Meter;
     Importer::Result result = importer->LoadFile (argv[1], params);
     if (result != Importer::Result::Success) {
         return 1;

occt-import-js/example/main.cpp

@@ -9,6 +9,7 @@
 #include <Bnd_Box.hxx>
 #include <BRepBndLib.hxx>
 #include <BRepMesh_IncrementalMesh.hxx>
+#include <UnitsMethods.hxx>
 
 VectorBuffer::VectorBuffer (const std::vector<uint8_t>& v)
 {
@@ -95,6 +96,25 @@ bool OcctFace::HasTriangulation () const
     return true;
 }
 
+UnitsMethods_LengthUnit LinearUnitToLengthUnit (ImportParams::LinearUnit linearUnit)
+{
+    UnitsMethods_LengthUnit lengthUnit = UnitsMethods_LengthUnit_Millimeter;
+    switch (linearUnit) {
+        case ImportParams::LinearUnit::Millimeter:
+            return UnitsMethods_LengthUnit_Millimeter;
+        case ImportParams::LinearUnit::Centimeter:
+            return  UnitsMethods_LengthUnit_Centimeter;
+        case ImportParams::LinearUnit::Meter:
+            return UnitsMethods_LengthUnit_Meter;
+        case ImportParams::LinearUnit::Inch:
+            return UnitsMethods_LengthUnit_Inch;
+        case ImportParams::LinearUnit::Foot:
+            return UnitsMethods_LengthUnit_Foot;
+        default:
+            return UnitsMethods_LengthUnit_Millimeter;
+    }
+}
+
 bool TriangulateShape (TopoDS_Shape& shape, const ImportParams& params)
 {
     Standard_Real linDeflection = params.linearDeflection;
@@ -112,7 +132,12 @@ bool TriangulateShape (TopoDS_Shape& shape, const ImportParams& params)
         Standard_Real avgSize = ((xMax - xMin) + (yMax - yMin) + (zMax - zMin)) / 3.0;
         linDeflection = avgSize * params.linearDeflection;
         if (linDeflection < Precision::Confusion ()) {
-            linDeflection = 0.1;
+            // use 1mm in the current unit
+            double mmToUnit = UnitsMethods::GetLengthUnitScale (
+                UnitsMethods_LengthUnit_Millimeter,
+                LinearUnitToLengthUnit (params.linearUnit)
+            );
+            linDeflection = 1.0 * mmToUnit;
         }
     }
 

occt-import-js/src/importer-utils.cpp

@@ -6,6 +6,7 @@
 #include <TopoDS_Face.hxx>
 #include <TopLoc_Location.hxx>
 #include <Poly_Triangulation.hxx>
+#include <UnitsMethods_LengthUnit.hxx>
 
 #include <vector>
 #include <fstream>
@@ -36,4 +37,5 @@ class OcctFace : public Face
     TopLoc_Location location;
 };
 
+UnitsMethods_LengthUnit LinearUnitToLengthUnit (ImportParams::LinearUnit linearUnit);
 bool TriangulateShape (TopoDS_Shape& shape, const ImportParams& params);

occt-import-js/src/importer-utils.hpp

@@ -371,26 +371,7 @@ Importer::Result ImporterXcaf::LoadFile (const std::vector<std::uint8_t>& fileCo
 {
     document = new TDocStd_Document ("XmlXCAF");
 
-    UnitsMethods_LengthUnit lengthUnit = UnitsMethods_LengthUnit_Millimeter;
-    switch (params.linearUnit) {
-        case ImportParams::LinearUnit::Millimeter:
-            lengthUnit = UnitsMethods_LengthUnit_Millimeter;
-            break;
-        case ImportParams::LinearUnit::Centimeter:
-            lengthUnit = UnitsMethods_LengthUnit_Centimeter;
-            break;
-        case ImportParams::LinearUnit::Meter:
-            lengthUnit = UnitsMethods_LengthUnit_Meter;
-            break;
-        case ImportParams::LinearUnit::Inch:
-            lengthUnit = UnitsMethods_LengthUnit_Inch;
-            break;
-        case ImportParams::LinearUnit::Foot:
-            lengthUnit = UnitsMethods_LengthUnit_Foot;
-            break;
-        default:
-            return Importer::Result::ImportFailed;
-    }
+    UnitsMethods_LengthUnit lengthUnit = LinearUnitToLengthUnit (params.linearUnit);
     XCAFDoc_DocumentTool::SetLengthUnit (document, 1.0, lengthUnit);
 
     if (!TransferToDocument (fileContent)) {