#3644 Write unit test for cell volume calculation and fix negative volumes for "flipped" cells.

ApplicationCode/ReservoirDataModel/RigCellGeometryTools.cpp

@@ -78,8 +78,8 @@ double RigCellGeometryTools::calculateCellVolume(const std::array<cvf::Vec3d, 8>
     // 2 flops for summation + 1 for division = 3 flops
     double volume = (det1 + det2 + det3) / 12.0;
     
-    // Assume 0 in volume for degenerate cells. 1 flop.
+    // In order for this to work in any rotation of the cell, we need the absolute value. 1 flop.
-    return std::max(0.0, volume); // Altogether 18 + 3*17 + 3 + 1 flops = 73 flops.
+    return std::abs(volume); // Altogether 18 + 3*17 + 3 + 1 flops = 73 flops.
 }
 
 //--------------------------------------------------------------------------------------------------

ApplicationCode/UnitTests/RigCellGeometryTools-Test.cpp

@@ -21,6 +21,27 @@
 #include "RigCellGeometryTools.h"
 #include "RigMainGrid.h"
 
+//--------------------------------------------------------------------------------------------------
+/// 
+//--------------------------------------------------------------------------------------------------
+TEST(RigCellGeometryTools, calculateCellVolumeTest)
+{
+    cvf::BoundingBox bbox(cvf::Vec3d(1.0, -2.0, 5.0), cvf::Vec3d(200.0, 3.0, 1500.0));
+    cvf::Vec3d extent = bbox.extent();
+    double bboxVolume = extent.x() * extent.y() * extent.z();
+
+    std::array<cvf::Vec3d, 8> cornerVertices;
+    bbox.cornerVertices(cornerVertices.data());    
+
+    EXPECT_DOUBLE_EQ(bboxVolume, RigCellGeometryTools::calculateCellVolume(cornerVertices));
+
+    cornerVertices[1].x() += 100.0;
+    cornerVertices[2].x() += 100.0;
+
+    double extraVolume = 0.5 * extent.z() * 100 * extent.y();
+
+    EXPECT_DOUBLE_EQ(bboxVolume + extraVolume, RigCellGeometryTools::calculateCellVolume(cornerVertices));
+}
 
 //--------------------------------------------------------------------------------------------------
 ///