Seperate line creation so it can be paralized

src/contour_creator.hh

@@ -36,3 +36,20 @@ class CellMap
         CellMap(int width, int height, uint8_t* cells, OGRSpatialReference reference_system, double* geotransform);
         int get_cell(int x,int y);
 };
+
+class Point
+{
+    public:
+        int x;
+        int y;
+        int mscase;
+        Point * next;
+        Point * previous;
+        Point(int x, int y, int mscase){
+            this -> x = x;
+            this -> y = y;
+            this -> mscase = mscase;
+            this -> next = nullptr;
+            this -> previous = nullptr;
+        };
+};

src/main.cpp

@@ -5,6 +5,7 @@
 #include <gdal/ogr_feature.h>
 #include <gdal/ogr_geometry.h>
 #include <iostream>
+#include <iterator>
 #include <ostream>
 #include <vector>
 #include <cstdint>
@@ -13,10 +14,11 @@
 #include <gdal/gdal_frmts.h>
 #include <omp.h>
 
-CellMap produce_cellmap(HeightMap* heightmap, float z)
+std::vector<Point> produce_cellmap(HeightMap* heightmap, float z)
 {
-    int length = (heightmap->width-1)*(heightmap->height-1);
+    int length = (heightmap->width-1)*(heightmap->height-1); // Defining length of vector
     uint8_t *cells = (uint8_t *) CPLMalloc(sizeof(uint8_t)*length);
+    std::vector<Point> points; // Initiating a vector of points
     for (int i = 0; i<length; i++) {
         int y = i/(heightmap->width-1);
         int x = i%(heightmap->width-1);
@@ -24,35 +26,16 @@ CellMap produce_cellmap(HeightMap* heightmap, float z)
         (heightmap->get_pixel(x+1,y)>z)*2 +
         (heightmap->get_pixel(x+1,y+1)>z)*4 +
         (heightmap->get_pixel(x,y+1)>z)*8;
-        *(cells + i) = result;
+        if (result != 0 and result != 15 ) {
+            points.push_back(Point(x, y, result));
+
+        };
     }
     
-    return CellMap(heightmap->width-1, heightmap->height-1, cells, heightmap->reference_system, heightmap->geotransform);
+    return points;
 
 
 }
-
-std::vector<CellMap> vector_cellmap(HeightMap* heightmap, int interval)
-{
-    int num_contours = (heightmap->max - heightmap->min)/interval;
-    std::vector<CellMap> vector_contours;
-    omp_set_num_threads(12);
-
-    #pragma omp parallel
-    {
-        std::vector<CellMap> vec_private;
-        #pragma omp for
-        for (int i = 1; i <= num_contours; i++) 
-        {
-            vec_private.push_back(produce_cellmap(heightmap, heightmap->min + interval*i));
-        }
-        #pragma omp critical
-        vector_contours.insert(vector_contours.end(), vec_private.begin(), vec_private.end());
-
-    }
-        return vector_contours;
-}
-
 std::tuple<double, double> local_to_projected(double* geotransform, int x, int y)
 {
     return {
@@ -62,6 +45,116 @@ std::tuple<double, double> local_to_projected(double* geotransform, int x, int y
         geotransform[4] * 0.5 + geotransform[5] * 0.5 + geotransform[3]
         };
 }
+std::vector<OGRFeature*> create_contours(OGRFeatureDefn* layer_def, std::vector<Point> points, HeightMap* heightmap)
+{
+    std::vector<OGRFeature*> lines;
+    for (int i = 0; i<points.size();i++)
+    {
+        OGRFeature *feature;
+            OGRLineString *geometry = new OGRLineString();
+            
+            feature = OGRFeature::CreateFeature(layer_def);
+            feature->SetField( "Name", i );
+        Point* current = &points[0];
+        int points_delegated = 0;
+        while (points_delegated < points.size()) 
+        {
+            //int x_raw = i%width;
+            //int y_raw = i/height;
+            int x_raw = current->x;
+            int y_raw = current->y;
+            auto [x, y] = local_to_projected(heightmap->geotransform, x_raw, y_raw);
+            //std::cout << x << ", " << y << "  ";
+            //auto [x_bl, y_bl, x_tr, y_tr] = marching_squares_lookup(*(cellmap->cells + i) );
+            //std::cout << x << ", " << y << "  ";
+            //geometry->setPoint( geometry->getNumPoints(), x+x_tr*0.25, y+y_tr*0.25 ); 
+            //geometry->setPoint( geometry->getNumPoints(), x+x_bl*0.25, y+y_bl*0.25 ); 
+            geometry->setPoint(geometry->getNumPoints(),x ,y );
+            points_delegated++;
+            current = current->next;
+            if (current == nullptr) 
+            {
+                for (int k = 0; k < points.size(); k++)
+                {
+                    if (points[k].previous == nullptr)
+                    {
+                    current = &points[k];
+                    }
+                }
+                if (current == nullptr)
+                {
+                    break;
+                }
+
+            }
+        }
+
+                    if ( feature->SetGeometry(geometry) != OGRERR_NONE)
+            {
+                printf( "Failed to set geometry.\n" );
+                exit( 1 );
+            }
+            OGRGeometryFactory::destroyGeometry(geometry);
+            lines.push_back(feature);
+    }
+    
+}
+
+std::vector<OGRFeature*> vector_cellmap(OGRFeatureDefn* layer_def, HeightMap* heightmap, int interval)
+{
+    int num_contours = (heightmap->max - heightmap->min)/interval;
+    std::vector<OGRFeature*> vector_contours;
+    omp_set_num_threads(12);
+
+    #pragma omp parallel
+    {
+        std::vector<OGRFeature*> lines;
+        #pragma omp for
+        for (int i = 1; i <= num_contours; i++) 
+        {
+            auto points = produce_cellmap(heightmap, heightmap->min + interval*i);
+
+                
+            for (int j = 0; j < points.size(); j++){
+                Point* current = &points[j];
+                //std::cout << points_allocated << " " << points.size() << "\n";
+                for (int k = 0; k < points.size(); k++){
+                    Point* candidate = &points[k];
+                    if (candidate->previous == nullptr) {
+                        
+                        if (candidate->x +1 == current->x && candidate->y == current->y) {
+                            current->next = candidate;
+                            candidate->previous = current;
+                        }
+                        else if (candidate->x -1 == current->x && candidate->y == current->y) {
+                            current->next = candidate;
+                            candidate->previous = current;
+                        }
+                        else if (candidate->y +1 == current->y && candidate->x == current->x) {
+                            current->next = candidate;
+                            candidate->previous = current;
+                        }
+                        else if (candidate->y -1 == current->y && candidate->x == current->x) {
+                            current->next = candidate;
+                            candidate->previous = current;
+                        }
+                        
+                    }
+                }
+            }
+            auto lines = create_lines(layer_def, points, heightmap);
+            
+        }
+        
+        #pragma omp critical
+
+        vector_contours.insert(vector_contours.end(), lines.begin(), lines.end());
+
+    }
+        return vector_contours;
+}
+
+
 
 constexpr std::tuple<double, double, double, double> marching_squares_lookup(int mcase)
 {
@@ -82,7 +175,9 @@ constexpr std::tuple<double, double, double, double> marching_squares_lookup(int
         case 14: return {0, 0.5, 0.5, 0};
     };
 }
-void write_output_file(std::vector<CellMap> cellmaps, const char *filepath)
+
+
+void write_output_file(const char *filepath, HeightMap* heightmap)
 {
 
     const char *pszDriverName = "GeoJSON";
@@ -108,7 +203,7 @@ void write_output_file(std::vector<CellMap> cellmaps, const char *filepath)
 
     OGRLayer *poLayer;
 
-    poLayer = poDS->CreateLayer( "contours", &(cellmaps[0]).reference_system, wkbLineString, NULL );
+    poLayer = poDS->CreateLayer( "contours", /*&(cellmaps[0]).reference_system*/ NULL, wkbLineString, NULL );
     if( poLayer == NULL )
     {
         printf( "Layer creation failed.\n" );
@@ -124,42 +219,23 @@ void write_output_file(std::vector<CellMap> cellmaps, const char *filepath)
         printf( "Creating Name field failed.\n" );
         exit( 1 );
     }
-    for (int j = 0; j < cellmaps.size(); j++)
+    int width = heightmap->width -1;
+    int height = heightmap->height -1;
+    int size = width * height;
+
+    // gets the lines from the heightmap. Runs the actual algorithm
+    auto lines = create_contours(poLayer->GetLayerDefn(), heightmap, 5);
+
+
+    for (int j = 0; j < lines.size(); j++)
     {
-        CellMap* cellmap = &cellmaps[j];
 
-        for (int i = 0; i < cellmap->height*cellmap->width; i++) 
+            if( poLayer->CreateFeature( lines[j] ) != OGRERR_NONE )
-        {
-            if (*(cellmap->cells + i) != 0 && *(cellmap->cells + i) != 15)
             {
-                OGRFeature *feature;
+                printf( "Failed to create feature in shapefile.\n" );
-                OGRLineString *geometry = new OGRLineString();
+                exit( 1 );
-                feature = OGRFeature::CreateFeature( poLayer->GetLayerDefn() );
+            }
-                feature->SetField( "Name", j );
+            OGRFeature::DestroyFeature( lines[j] );  
-                int x_raw = i%cellmap->width;
-                int y_raw = i/cellmap->width;
-                auto [x, y] = local_to_projected(cellmap->geotransform, x_raw, y_raw);
-                auto [x_bl, y_bl, x_tr, y_tr] = marching_squares_lookup(*(cellmap->cells + i) );
-                //std::cout << x << ", " << y << "  ";
-                geometry->setPoint( geometry->getNumPoints(), x+x_tr*0.25, y+y_tr*0.25 ); 
-                geometry->setPoint( geometry->getNumPoints(), x+x_bl*0.25, y+y_bl*0.25 ); 
-                
-
-                if ( feature->SetGeometry(geometry) != OGRERR_NONE)
-                {
-                    printf( "Failed to set geometry.\n" );
-                    exit( 1 );
-                }
-                OGRGeometryFactory::destroyGeometry(geometry);
-                if( poLayer->CreateFeature( feature ) != OGRERR_NONE )
-                {
-                    printf( "Failed to create feature in shapefile.\n" );
-                    exit( 1 );
-                }
-                OGRFeature::DestroyFeature( feature );  
-                    }
-            
-        }
         
 
     }
@@ -179,6 +255,6 @@ int main(int argc, const char* argv[])
     
     auto cellmap = produce_cellmap(&map, 40);
     
-    auto cellmaps = vector_cellmap(&map, 5);
+    
-    write_output_file(cellmaps, "out.geojson");
+    write_output_file("out.geojson", &map);
 }