Small area flow compensator improvements (#11716)

* Replace spline with PchipInterpolatorHelper in flow compensator

Swapped out the tk::spline implementation for PchipInterpolatorHelper in SmallAreaInfillFlowCompensator. Updated member types and method calls to use the new interpolator for improved flow compensation modeling.

* Enforce strictly increasing flow compensation factors

Added a check to ensure that flow compensation factors in SmallAreaInfillFlowCompensator strictly increase with extrusion length, throwing an exception if this condition is not met. This improves input validation and prevents invalid compensation models.

* Add context to Small Area Flow Compensation errors

Prefixed error messages in SmallAreaInfillFlowCompensator with 'Small Area Flow Compensation' for improved clarity and debugging. Also rethrows exceptions after logging to ensure proper error propagation.

* Remove spline library from dependencies

Eliminated the spline header-only library from the project by deleting its CMake configuration and header file, and updating documentation and build scripts to remove references to spline. This streamlines the dependencies and build process.

src/libslic3r/GCode/SmallAreaInfillFlowCompensator.cpp

@@ -15,7 +15,6 @@
 #include "../PrintConfig.hpp"
 
 #include "SmallAreaInfillFlowCompensator.hpp"
-#include "spline/spline.h"
 #include <boost/log/trivial.hpp>
 
 namespace Slic3r {
@@ -47,37 +46,43 @@ SmallAreaInfillFlowCompensator::SmallAreaInfillFlowCompensator(const Slic3r::GCo
                     }
                 } catch (...) {
                     std::stringstream ss;
-                    ss << "Error parsing data point in small area infill compensation model:" << line << std::endl;
+                    ss << "Small Area Flow Compensation: Error parsing data point in small area infill compensation model:" << line << std::endl;
 
                     throw Slic3r::InvalidArgument(ss.str());
                 }
             }
         }
 
-        for (int i = 0; i < eLengths.size(); i++) {
+        for (size_t i = 0; i < eLengths.size(); i++) {
             if (i == 0) {
                 if (!nearly_equal(eLengths[i], 0.0)) {
-                    throw Slic3r::InvalidArgument("First extrusion length for small area infill compensation model must be 0");
+                    throw Slic3r::InvalidArgument("Small Area Flow Compensation: First extrusion length for small area infill compensation model must be 0");
                 }
             } else {
                 if (nearly_equal(eLengths[i], 0.0)) {
-                    throw Slic3r::InvalidArgument("Only the first extrusion length for small area infill compensation model can be 0");
+                    throw Slic3r::InvalidArgument("Small Area Flow Compensation: Only the first extrusion length for small area infill compensation model can be 0");
                 }
                 if (eLengths[i] <= eLengths[i - 1]) {
-                    throw Slic3r::InvalidArgument("Extrusion lengths for subsequent points must be increasing");
+                    throw Slic3r::InvalidArgument("Small Area Flow Compensation: Extrusion lengths for subsequent points must be increasing");
                 }
             }
         }
 
-        if (!flowComps.empty() && !nearly_equal(flowComps.back(), 1.0)) {
-            throw Slic3r::InvalidArgument("Final compensation factor for small area infill flow compensation model must be 1.0");
+        for (size_t i = 1; i < flowComps.size(); ++i) {
+            if (flowComps[i] <= flowComps[i - 1]) {
+                throw Slic3r::InvalidArgument("Small Area Flow Compensation: Flow compensation factors must strictly increase with extrusion length");
+            }
         }
 
-        flowModel = std::make_unique<tk::spline>();
-        flowModel->set_points(eLengths, flowComps);
+        if (!flowComps.empty() && !nearly_equal(flowComps.back(), 1.0)) {
+            throw Slic3r::InvalidArgument("Small Area Flow Compensation: Final compensation factor for small area infill flow compensation model must be 1.0");
+        }
+
+        flowModel = std::make_unique<PchipInterpolatorHelper>(eLengths, flowComps);
 
     } catch (std::exception& e) {
         BOOST_LOG_TRIVIAL(error) << "Error parsing small area infill compensation model: " << e.what();
+        throw;
     }
 }
 
@@ -92,7 +97,7 @@ double SmallAreaInfillFlowCompensator::flow_comp_model(const double line_length)
         return 1.0;
     }
 
-    return (*flowModel)(line_length);
+    return flowModel->interpolate(line_length);
 }
 
 double SmallAreaInfillFlowCompensator::modify_flow(const double line_length, const double dE, const ExtrusionRole role)

src/libslic3r/GCode/SmallAreaInfillFlowCompensator.hpp

@@ -4,12 +4,9 @@
 #include "../libslic3r.h"
 #include "../PrintConfig.hpp"
 #include "../ExtrusionEntity.hpp"
+#include "PchipInterpolatorHelper.hpp"
 #include <memory>
 
-namespace tk {
-class spline;
-} // namespace tk
-
 namespace Slic3r {
 
 class SmallAreaInfillFlowCompensator
@@ -26,8 +23,7 @@ private:
     std::vector<double> eLengths;
     std::vector<double> flowComps;
 
-    // TODO: Cubic Spline
-    std::unique_ptr<tk::spline> flowModel;
+    std::unique_ptr<PchipInterpolatorHelper> flowModel;
 
     double flow_comp_model(const double line_length);