Added parameter for pillar connection mode

src/libslic3r/SLA/SLASupportTree.cpp

@@ -1249,8 +1249,13 @@ bool SLASupportTree::generate(const PointSet &points,
             if(chkd >= bridge_distance) {
                 result.add_bridge(sj, ej, pillar.r);
 
+                auto pcm = cfg.pillar_connection_mode;
+
                 // double bridging: (crosses)
-                if(pillar_dist > 2*cfg.base_radius_mm) {
+                if( pcm == PillarConnectionMode::cross ||
+                   (pcm == PillarConnectionMode::dynamic &&
+                    pillar_dist > 2*cfg.base_radius_mm))
+                {
                     // If the columns are close together, no need to
                     // double bridge them
                     Vec3d bsj(ej(X), ej(Y), sj(Z));

src/libslic3r/SLA/SLASupportTree.hpp

@@ -28,6 +28,12 @@ using SlicedSupports = std::vector<SliceLayer>;
 
 namespace sla {
 
+enum class PillarConnectionMode {
+    zigzag,
+    cross,
+    dynamic
+};
+
 struct SupportConfig {
     // Radius in mm of the pointing side of the head.
     double head_front_radius_mm = 0.2;
@@ -46,6 +52,9 @@ struct SupportConfig {
     // headless pillars will have half of this value.
     double headless_pillar_radius_mm = 0.4;
 
+    // How to connect pillars
+    PillarConnectionMode pillar_connection_mode = PillarConnectionMode::dynamic;
+
     // TODO: unimplemented at the moment. This coefficient will have an impact
     // when bridges and pillars are merged. The resulting pillar should be a bit
     // thicker than the ones merging into it. How much thicker? I don't know